PROPOSAL PROGRAM RISET DAN INOVASI ITB 2011

PROPOSAL PROGRAM RISET DAN INOVASI ITB 2011

Pengembangan metoda pemantauan aktivitas gunungapi berdasarkan pada sifat listrik dan magnetik Development of method for monitoring volcanic activity derived from electrical and magnetic properties

Ketua Tim Peneliti: Dr. Nurhasan, S.Si, M.Si

KK

: Fisika Sistem Kompleks

Fakultas/Sekolah : FMIPA

INSTITUT TEKNOLOGI BANDUNG September, 2010

DAFTAR ISI Halaman IDENTITAS PROPOSAL ..................................................................................................3 1

RINGKASAN PROPOSAL ..........................................................................................4

2

PENDAHULUAN ......................................................................................................5 2.1

Latar belakang masalah ...................................................................................5

2.2

Tujuan riset....................................................................................................6

3

METODOLOGI...................................................................................................... 11

4

DAFTAR PUSTAKA ................................................................................................ 14

5

INDIKATOR KEBERHASILAN (TARGET CAPAIAN) ..................................................... 15

6

JADWAL PELAKSANAAN ........................................................................................ 16

7

PETA JALAN (ROAD MAP) RISET ............................................................................ 17

8

USULAN BIAYA RISET ........................................................................................... 18 8.1

Belanja pegawai............................................................................................ 18

8.2

Belanja barang ............................................................................................. 18

8.3

Belanja jasa.................................................................................................. 18

9

CV TIM PENELITI ................................................................................................. 20

10

LAMPIRAN BUKTI CAPAIAN OUTPUT TAHUN 2009-2010........................................... 29

3 LEMBAR IDENTITAS 1. Judul

: Pengembangan metoda pemantauan aktivitas gunungapi berdasarkan pada sifat listrik dan magnetik

2. Tim Peneliti 2.1 Peneliti Utama a. Nama Lengkap b. Pangkat/Golongan/Jabatan c. NIP d. Fakultas/Sekolah e. Kelompok Keilmuan f. Telpon/Fax Kantor g. Email h. Alamat Rumah i. Telpon Pribadi

: Dr. Nurhasan S.Si.,M.Si. : Penata Muda Tk. I/IIIB/Asisten Ahli : 132231594 : Fakultas Matematika dan Ilmu Pengetahuan Alam : Fisika Sistem Kompleks : 022-2500834 / : [email protected] : Komplek Pasir Pogor Blok RC No.9 Bandung : 081394276972

2.2 Anggota Tim Peneliti No.

Nama dan Gelar Akademik

Bidang Keahlian

Unit Kerja

Jam/mg

Bulan

1.

Prof. Doddy Sutarno, M.Sc, Ph.D

Induksi ELektromagnetik

FMIPA ITB

5

10

2.

Dr.rer.nat. Sparisoma Viridi, S.Si

Pemodelan Numerik

FMIPA ITB

5

10

2.2 Asisten Peneliti/Mahasiswa No.

Nama dan Gelar Akademik

Bidang Keahlian

Status

Jam/mg

Bulan

1.

Imran Hilman,S.Si, M.Si

Pemodelan Numerik

Mhs S3

10

10

2.

Harsya Bachtiar

Akusisi data

Mhs S1

10

10

3. Biaya yang diusulkan 4. Urutan Prioritas Skema

: Rp. 50.000.000,00 : 1. Riset Desentralisasi DP2M Dikti (STRANAS) 2. Riset dan Inovasi KK 3. Riset The Osaka Gas Foundation

5. Target output (keluaran) Riset No.

: Nama/Jenis Output

Jumlah

1.

Jurnal Nasional ber-referee/terakreditasi

2

2.

Prosiding Konferensi Internasional

1

6. Proposal ini belum pernah didanai oleh atau diusulkan ke sumber lain. Mengetahui Ketua Kelompok Keahlian

Bandung, 30 September 2010 Peneliti Utama

(Dr.rer.nat. Umar Fauzi ) NIP: 131844768

(Dr. Nurhasan S.Si.,M.Si.) NIP: 132231594

Dekan Fakultas Matematika dan Ilmu Pengetahuan Alam

(Prof. Dr. Pudji Astuti Waluyo MS) NIP: 131572750

4 1. RINGKASAN PROPOSAL

Indonesia sebagai salah satu negara kepulauan yang terletak pada batas tumbukan lempeng lempeng dunia merupakan negara yang memiliki resiko bencana alam tinggi terutama bencana alam gempa bumi dan letusan gunungapi. Sebagian besar gunungapi di Indonesia masih aktif dan terletak di daerah pemukiman yang sewaktu waktu dapat menimbulkan bencana bagi penduduk disekitarnya jika terjadi peningkatan aktivitas gunungapi apalagi jika sampai terjadi letusan. Berbagai usaha telah dan sedang diupayakan pemerintah dalam rangka mitigasi bencana baik dalah hal pengembangan pemantauan aktivitas gunungapi maupun dalam upaya meminimalisasi dampak kerugian yang ditimbulkan oleh bencana alam gunungapi ini. Salah satu sistem pemantauan aktivitas gunungai yang saat ini digunakan adalah data seismik yang didasarkan pada besar kecilnya getaran yang ditimbulkan oleh aktivitas gunungapi. Dalam penelitian ini akan di kembangkan suatu metoda alternatif dalam memantau aktivitas gunungapi dengan menggunakan metoda

elektromagnetik dan magnetik. Dalam metoda

yang diusulkan ini, perubahan struktur bawah gunungapi akan dipantau berdasarkan paramter fisis resistivitas sedangkan metoda magnetik digunakan untuk memantau perubahan sifat magnetik yang berhubungan dengan perubahan temperatur bawah permukaan, sehingga pemantauan gunungapi akan lebih komprehenship dan terintegrasi, dengan demikian informasi yang diperoleh akan lebih akurat. Metoda elektromagnetik merupakan metoda geofisika yang sangat sensitif terhadap perubahan konduktifitas dibawah permukaan bumi sebagai akibat berubahnya temperatur. Dengan memantau perubahan keberadaan daerah konduktif dan sifat magnetik akibat perubahan temperatur yang berhubungan dengan aditivitas gunungapi, maka pemantauan aktivitas gunungapi dapat diperoleh sehinga diharapkan informasi yang lebih detail, akurat dan komprehensif bisa didapatkan yang pada akhirnya dampak negatif dari kegiatan gunungapi bisa diantisipasi lebih dini.

5 2. PENDAHULUAN 2.1. Latar Belakang Negara Indonesia selain merupakan negara kepulauan, juga merupakan negara yang mempunyai banyak gunungapi aktif. Tidak kurang dari 129 gunungapi aktif atau 13%-17% dari jumlah gunungapi di dunia terdapat di Indonesia. Oleh karena itu, informasi aktivitas gunungapi yang lebih akurat dan komprehensif mutlak diperlukan. Monitoring gunung dapat dilakukan dengan beberapa metoda yang sudah dan sedang dikembangkan diantaranya dengan metoda seismik, metoda GPS (Hasanuddin et al., 2001). Sumber informasi tentang aktivitas gunungapi yang paling diandalkan pada saat ini adalah data seimik yang didasarkan pada besar kecilnya getaran yang terjadi. Peralatan seismik ini dipasang di sekitar gunungapi untuk medapatkan data berupa peningkatan atau penurunan getaran akibat aktivitas gunungapi. Data yang diperoleh pada metoda ini berupa data secara real time yang direkam berdasarkan phenomena yang terjadi dipermukaan pada saat itu tanpa melibatkan secara langsung informasi dari struktur bawah permukaan tubuh gunungapi secara keseluruhan. Dalam penelitian ini, berbeda dengan metoda yang selama ini digunakan, kami akan mengaplikasikan dan mengembangkan metoda elektromagnetik dan magnetik untuk mendeteksi perubahan struktur bawah gunungapi berdasarkan parameter

fisis

resistivitas

dan

sifat

magnetiknya.

Kelebihan

metoda

elektromagnetik dalam memetakan tubuh gunungapi dibandingkan dengan metoda geofisika lainnya adalah sensitifitasnya yang sangat tinggi terhadap kontras resistivitas atau konduktivitas bawah permukaan (Nurhasan, et al., 2006). Interpretasi data akan dilakukan melalui pemodelan elektromagnetik tiga dimensi. Sementara itu, sifat magnetik suat batuan sangat berhubungan erat dengan aktivitas gunungapi karena adanya perubahan temperatur akibat menaiknya panas kepermukaan. Dengan menggunakan kedua metoda ini diharapkan hasil pemodelan akan lebih baik sehingga informasi yang didapat lebih akurat. Analisa perubahan

daerah

konduktif,

sifat

magnetik

dan

hubungannya

dengan

sifat/parameter fisis yang lain (temperatur) akan memberikan informasi yang lebih komprehensif dan terintegrasi tentang aktivitas gunungapi yang terjadi sehingga

6 informasi yang didapat bukan saja bermanfaat pada waktu itu tetapi juga dapat dijadikan acuan untuk memprediksi aktivitas dalam jangka panjang. 2.2. Signifikansi Penelitian Salah satu isu nasional dalam penanganan bencana yang diakibatkan oleh meningkatnya aktivitas gunungapi adalah terbatasnya data yang diperoleh baik secara kuantitas maupun secara kualitas. Untuk mendapatkan informasi yang akurat dan komprehensif tentang aktivitas gunungapi, diperlukan suatu sarana yang dapat menggambarkan proses/aktivitas gunungapi secara menyeluruh baik yang melibatkan pendeteksian phenomena di permukaan seperti getaran atau deformasi maupun pendeteksian informasi tentang struktur tubuh gunungapi secara menyeluruh. Pemetaan struktur bawah permukaan gunungapi yang menyeluruh merupakan hal yang sangat penting untuk mengetahui proses yang terjadi di dalam tubuh gunungapi itu sendiri. Dengan menganalisa proses dan aktivitas yang terjadi pada tubuh gunungapi, diharapkan dapat memberikan informasi tentang kondisi aktivitas gunungapi aat itu. Diperlukan suatu metoda lain yang dapat memberikan informasi secara akurat dan lebih konprehensif dari aktivitas gununga api. Metoda elektromagnetik merupakan metoda alternatif untuk memantau aktivitas gunungapi. Dari segi pemodelan, diperlukan suatu metodologi dan teknik yang dapat meminimalisasi adanya efek efek yang dianggap sebagai nois seperti efek distorsi galvanik (galvanic distortion) yang biasa terjadi pada data elektromagnetik khususnya data magnetotellurik. Dengan melakukan pengembangan baik dari segi pemanfaat teknologi maupun pengembangan teknik pemodelan, diharapkan data yang diperoleh tidak saja berguna untuk saat itu (real time) tetapi juga dapat digunakan untuk mempelajari aktivitas gunug api di waktu

yang akan datang sehingga

penanganan bencana dapat dilakukan lebih awal yang pada akhirnya akan mengurangi dampak negatif dari aktivitas gunungapi. 2.3. Tujuan Penelitian Tujuan dilaksanakannya penelitian ini adalah 1. Memanfaatkan metoda elektromagnetik dan metoda magnetik dalam memantau aktivitas gunungapi di Indonesia.

7 2. Mengembangkan pemodelan elektromagnetik untuk memetakan struktur resistivitas bawah permukaan didaerah gunungapi. 3. Melalui kerjasama dengan instansi terkait (Direktorat Vulkanologi), akan menyediakan data/inofrmasi yang lebih baik dan akurat tentang aktivitas gunungapi yang selanjutnya dapat dijadikan untuk keperluan MITIGASI BENCANA ALAM di Indonesia 2.4. TINJAUAN PUSTAKA Pemantauan aktivitas gunungapi akan lebih efektif dan bermanfaat jika data yang diperoleh tidak saja menggambarkan aktivitas pada saat itu tetapi juga bisa memprediksi aktivitas gunungapi dalam jangka panjang. Beberapa metoda yang sejak dulu dan sekarang digunakan untuk mengetahui aktivitas gunungapi diantaranya adalah metoda seismik, metoda GPS, metoda satelit. Metoda Seismik adalah metoda yang digunakan dengan melakukan pemantauan getaran yang ditimbulkan oleh aktivitas gunungapi. Peningkatan aktivitas gunungapi dicirikan oleh makin tinggi dan seringnya getaran yang terjadi. Alat yang digunakan pada metoda ini berupa alat seismograf yang dapat merekam data getaran yang ditempatkan di daerah sekitar gunungapi. Sedangkan metoda GPS adalah metoda yang memanfaatkan perubahan/deformasi permukaan tanah yang terjadi sebagai akibat aktivitas gunungapi. Metoda metoda tersebut pada umumnya memanfaatkan phenomena yang terjadi pada saat aktivitas gunungapi meningkat. Selain itu, dalam metoda tersebut, data yang diperoleh merupakn sinyal yang terekam dipermukaan tanpa melibatkan secara langsung informasi proses dalam tubuh gunungapi itu sendiri. Struktur bawah permukaan gunungapi sangat kompleks. Struktur ini dapat di pelajari dalam berbagai parameter fisis misalnya resistivitas/konduktivitas, massa jenis, sifat magnetik, data kecepatan gelombang seismik, dan lain lain.

8 Perubahan resistivitas terhadap aktivitas gunungapi

Diantara parameter fisis tersebut, resistivitas merupakan parameter yang dapat dijadikan acuan dalam memantau aktivitas gunungapi. Hal ini disebabkan nilai resistivitas/konduktivitas batuan berhubungan dengan kandungan lempung (clay). Hubungan konduktivitas dengan kandungan lempung (clay) dirumuskan dalam persamaan berikut (Waxman and Smits, 1968) :

(1) adalah konduktivitas batuan, F adalah formation factor, w adalah kondutivitas air dan  adalah konduktivitas yang berhubungan dengan perpindahan kation pada lempung. Pada gunungapi yang bertipe preatik, peningkatan aktivitas gunungapi berhubungan erat dengan kandungan lempung (clay) sebagai akibat menaiknya temperatur

dibawah

permukaan.

Hubungan

antara

temperatur

dengan

pembentukan lempung (clay) dapat ditemukan dalam beberapa referensi seperti di daerah Salton Sea, California (Jennings and Thompson, 1986), New Zeeland (Harvey and Browne, 1991), Nesjavellir, Iceland (Arnason et al, 2000), Awibengkok, Indonesia (Gunderson et al, 2000), Gunungapi Kusatsu-Shirane, Japan (Kurasawa, 1993). Keberadaan lempung (clay) dalam struktur gunungapi dan hubungannya dengan sebaran resistivitas dapat dijumpai pada referensi Nurhasan et al., 2006. Dengan demikian, pemetaan daerah konduktif di daerah gunungapi merupakan langkah yang sangat penting untuk menganalisa kandungan lempung dan hubungannya dengan aktivitas gunungapi. Untuk tujuan ini, metoda elektromagnetik merupakan metoda yang paling efektif untuk digunakan, karena parameter yang digunakan adalah resistivitas dan kemampuannya untuk mendeteksi dan memetakan kontras konduktivitas sampai kedalaman sekitar 3 km dari permukaan.

9 Perubahan sifat magnetik batuan terhadap aktivitas gunungapi

Meningkatnya aktivitas gunungapi dicirikan dengan naiknya temperatur yang berasal dari magma menuju ke permukaan. Batuan bawah permukaan gunungapi akan mengalami perubahan magnetisasinya ketika temperatur yang melewatinya

mengalami

magnetisasinya

menjadi

perubahan. bahan

yang

Bahan

magnetik

magnetisasinya

akan

berubah

berkurang

jika

temperaturnya menaik. Dengan demikian, perubahan sifat magnetik batuan di daerah gunungapi aktif akan memberikan informasi tentang tingkat aktivitas gunungapi tersebut. Semakin meningkat aktivitasnya, maka temperaturnya akan semakin tinggi yang menyebabkan sifat magnetik batuannya akan cenderung kearah sifat diamagnetik (Yamazaki et al., 1990, Koike et al., 2003). Perubahan sifat magnetik batuan ini akan diukur melalui survey magnetik yang akan dilakukan secara berkala dalam periode tertentu sehingga dapat diperoleh perubahan sifat magnetiknya. Pada tahun 1990, Yamazaki et al. (1990), telah melakukan pengukuran geomagnetic di gunungapi Kusatsu, Jepang secara berulang dan diperoleh hasil bahwa terdapat hubungan yang erat antara data magnetik dengan meningkatnya aktivitas gunungapi tersebut. Beberapa hasil pemodelan elektromagnetik dan hubungannya dengan gunungapi yang sudah dan sedang kami kembangkan dalam berbagai penelitian diantaranya :

I. Publikasi Ilmiah

1. Nurhasan , Y. Ogawa , N. Ujihara, S.B. Tank , Y. Honkura, S. Onizawa,, T. Mori , and M. Makino, 2006, Two electrical conductors beneath KusatsuShirane volcano, Japan, imaged by audiomagnetotellurics and their implications for hydrothermal system, Earth Planets Space, vol. 53, 1053 1059. 2. Nurhasan , Y. Ogawa, N. Ujihara , S.B. Tank , Y. Honkura , Teruo Yamawaki, maging of Hydrothermal System in Kusatsu-Shirane Volcano,

10 Japan, using Three Dimensional Magnetotelluric Inversion, The IAGA 11th Scientific Assembly, Sopron, August 23-30, 2009. 3. Nurhasan , D. Sutarno , Y. Ogawa , D. Sugiyanto , M Irwan, F. Kimata, Takeo Ito, Agustan, Investigation of Sumatra Fault based on Magnetotelluric and GPS Measurements, The IAGA 11th Scientific Assembly, Sopron, August 23-30, 2009. 4. Nurhasan , D. Sutarno, W. Srigutomo, E J Mustopa, U. Fauzi,Y. Ogawa, Three-Dimensional Resistivity Structure of Papandayan Volcano, Indonesia derived from Magnetotelluric Data, Pertemuan Ilmiah Tahunan Himpunan Ahli Geofisika Indonesia (PIT HAGI), Yogyakarta, 9 – 12 November 2009 5. Nurhasan , D. Sutarno, Y. Ogawa, Dimensionality Analysis of Resistivity Structure of Volcanic Zone from Magnetotelluric Data, Pertemuan Ilmiah Tahunan Himpunan Ahli Geofisika Indonesia (PIT HAGI), Yogyakarta, 9 – 12 November 2009.Geomagnetism Meeting, Tokyo, 2009 6. Pengembangan metoda Robust pada impedansi magnetotelluric (Sutarno, D., 2006).

II. Kelengkapan Peralatan Untuk keperluan survey dan pemodelan, laboratorium yang berada di KK Fisika Sistem Komplek memiliki fasilitas lengkap untuk menunjang kelangsungan Penelitian ini, diantaranya peralatan magnetik, resistivitas dan beberapa komputer dengan momeri yang cukup besar.

III. Hasil penelitian di Gunungapi Papandayan berdasarkan resistivitasnya diperlihatkan pada gambar dibawah ini.

11 Utara

Kawah

Gambar 1. Distribusi resistivitas pada daerah gunungapi Papandayan (Hasil penelitian KNRT 2008-2009) 3. METODOLOGI

Metodologi yang akan digunakan dalam penelitian ini meliputi : 1. Aspek Pemanfaatan metoda elektromagnetik Pengambilan data elektromagnetik sudah kami lakukan dapa penelitian penelitian sebelumnya sehingga pada penelitian ini, pengambilan data elektromagnetik

merupakan

data

untuk

mengetahui

sejauh

mana

perubahannya. 2. Aspek pemanfaatan metoda magnetik Survey metoda magnetik akan dilakukan secara berkala untuk mengetahui perubahan yang terjadi sebagai akibat meningkatnya/menurunkan akktivitas gunungapi.

Pengukuran akan dilakukan di gunungapi Papandayan, Garut

karena gunungapi ini baru meletus dan masih dalam proses aktif sehingga diharapkan dapat dilihat perubahan aktivitasnya. 3. Aspek Pemodelan Elektromganetik dan Magnetik Fokus

utama

pada

penelitian

ini

adalah

pembuatan

pemodelan

elektromagnetik yang memiliki tingkat kecepatan hitung dan keakurasian tinggi. Untuk mendapatkan hasil yang lebih baik dalam rangka tersedianya model

12 awal

yang

lebih

mendekati

model

sebenarnya,

maka

diperlukan

pengembangan pemodelan baik 1 dimensi maupun 2 dimensi. Pada tahap kedua ini, pemodelan difokuskan : a. Penyempurnaan pemodelan elektromagnetik yaitu : i. Pemodelan 2 dimensi sebagai sarana untuk mendapatkan masukan model awal untuk pemodelan 3 dimensi ii. Pemodelan 3 dimensi b. Pengujian Pemodelan dengan data sintetik c. Aplikasi unutuk data lapangan (data MT) d. Analisa dan interpretasi hasil pemodelan Urutan dalam penelitian ini sebagai berikut : 1. Studi Literatur , dikhususkan pada data data pendukung untuk daerah gunungapi yang akan diteliti. 2. Penyempurnaan pemodelan elektromagnetik yang meliputi : o Pemodelan 1 dan 2 dimensi o Pemodelan tiga dimensi. 3. Pengetesan program pemodelan tersebut dengan menggunakan data sintetik 4. Melakukan simulasi monitoring gunungapi dengan menggunakan data sintetik 5. Pengambilan data ke-1 6. Pemetaan resistiivtas dan sifat magnetik bawah permukaan gunungapi 7. Pengambilan data ke-2 8. Pemetaan resistiivtas dan sifat magnetik bawah permukaan gunungapi 9. Pengambilan data ke-3 10. Pemetaan resistiivtas dan sifat magnetik bawah permukaan gunungapi 11. Dari 3 data yang berbeda waktu, akan di buat monitoring gunungapi yang akan dikombinasikan dengan data geofisika lain. Aspek penelitian tersebut digambarkan pada diagram dibawah ini.

13

MITIGASI BENCANA ALAM

MONITORING GUNUNGAPI METODA SAAT INI Sumber Informasi : Phenomena yang terdeteksi dipermukaan bumi (getaran, deformasi )

METODA YANG DIUSULKAN

Sumber Informasi : Proses aktivitas gunung api secara komprehensif dan terintegrasi

Perubahan temperatur

Pemodelan Elektromagnetik dan Magnetik

Perubahan resistivitas :

Perubahan sifat magnetik Metoda Magnetik

Metoda Elektromagnetik

Gambar 2. Diagram kerangka konseptual monitoring gunungapi dengan metoda EM dan Magnetik

14 4. DAFTAR PUSTAKA

Cagniard, L., Basic theory of the magnetotelluric method of geophysical prospecting. Geophysics, 18, p.605, 1953 Groom, R. W. and R.C. Bailey, Decomposition of magnetotelluric impedance tensor in the presence of local three-dimensional galvanic distortion, J. Geophys. Res., 94, 1913–1925, 1989. Hasanuddin, Z.A, et al., Studi Deformasi Gunung Kelut Dengan Metode Survei GPS , Prosiding PIT HAGI ke – 26, Jakarta, 2001 Hohmann, G..W., Three-dimensional EM Modeling, Geophysical Survey , 6, 27-53, 1983. Kurasawa, T., Problem with the drilling of geothermal well in the south of Mt. Kusatsu-Shirane, Gunma Prf., J. Japan Geothermal Energy Assoc., 30, 1-23, 1993 (in Japanese with English Abstract). Muller A, and V. Haak, 3-D modeling of the deep electrical conductivity of Merapi volcano (Central Java): integrating magnetotellurics, induction vectors and the effects of steep topography, J. Volcano. Geotherm. Res., 138 (3-4): 205222, 2004. Nurhasan , Y. Ogawa , N. Ujihara, S.B. Tank , Y. Honkura, S. Onizawa,, T. Mori , and M. Makino, Two electrical conductors beneath Kusatsu-Shirane volcano, Japan, imaged

by audiomagnetotellurics and

their implications for

hydrothermal system, Earth Planets Space, 2006, vol. 53, 1053 - 1059. Ogawa, Y., On two-dimensional modeling of magnetotelluric field data, Surv. Geophys., 23 (2-3), 251-273, 2002. Ogawa, Y., N. Matsushima, H. Oshima, S. Takakura, M. Utsugi, K. Hirano, M. Igarashi, and T. Doi, A resistivity cross-section of Usu volcano, Hokkaido, Japan, by audiomagnetotellurics soundings, Earth Planets Space, 50, 339346, 1998. Ogawa, Y. and T. Uchida, A two-dimensional magnetotelluric inversion assuming Gaussian static shift, Geophys. J. Int., 126, 69–76, 1996. Shi,

X.,

H.

Utada,

J.

Wang,

W.

Siripunvaraporn,

Three-dimensional

magnetotelluric forward modeling using vector finite method combined with divergence correction based on the magnetic fields (VFEH++),

15 Siripunvaraporn, W., G. Egbert, An efficient data-subspace inversion method for 2D magnetotelluric data, Geophysics, 65,3, 791-803, 2000. Sutarno,

D.,

(2006).

Development

of

Robust

Magnetotelluric

Impedance

Estimation, Indonesian Journal of Physics, 16, no. 3, 81 - 91 Srigutomo, W., Sutarno, D. and Harja, A. (2006). 2-D Magnetotellurics numerical modeling using the boundary element method, International Conference on Mathematics and Natural Sciences, Bandung . Waxman, M.H., L.J.M. Smits, Electrical Conductivities in Oil-Bearing Shaly Sands, Society of Petroleum Engineers Journal, 243, 107-122, 1968 Saito, A., Experimental study on the demagnetization of rocks under interaction with acid geothermal fluid, Master thesis, Tokyo Institute of Technology, 42pp, (in Japanese) 2003 Yamazaki, A., Churei,M., Tsunomura, S., and Nakajima, S., Analysis of the variation of geomagnetic total force at Kusatsu-Shirane volcano: the remarkable changes in the geomagnetic total force in 1990 and the estimated thermal demagnetization model, Mem. Kakioka Mag. Obs., 24, 2, 53-66, 1992. (in Japanese with English abstract).

5. Target output (keluaran) Riset No. Nama/Jenis Output 1. Jurnal Nasional ber-referee/terakreditasi 2.

Prosiding Konferensi Internasional

: Jumlah 2 1

16 6. JADWAL PENELITIAN

KEGIATAN 1. 2. 6. 7. 6. 7. 6. 7. 5.

Studi Literatur Pemodelan elektromagnetik dan magnetik Akuisisi data ke-1 Gunungapi Prosesing data ke -1 Gunungapi Akuisisi data ke-2 Gunungapi Prosesing data ke -2 Gunungapi Akuisisi data ke-3 Gunungapi Prosesing data ke -3 Gunungapi Pembuatan Pemodelan dan Simulasi monitoring Gunungapi dengan data sintetik 9. Interpretasi data secara keseluruhan 10. Laporan kegiatan

BULAN KE1 2 3 4 5 6 7

8 9 10

17 7. PETA JALAN (ROAD MAP) PENELITIAN

Tahap Pengembangan 2006 - 2010

Tahap Inisiasi 2000 - 2005

Inventarisasi Software – software yang sudah di buat meliputi : - Pemodelan kedepan 1D dan 2D elektromganetik (MT dan CSAMT - Teknik teknik pengolahan data

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Pengembangan pemodelan kearah inversi baik 1D dan 2D Elektromganetik Pengembangan Pengambilan dan Pengolahan data elektromagnetik Pembuatan pemodelan 3 dimensi elektromagnetik

Tahap Lanjut 2010 - 2020

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Pengembangan pemodelan 3 dimensi baik forward maupun inversi Pembuatan software secara terintegrasi yang meliputi 1D, 2D dan 3 D Pengembangan pengolahan data elektromganetik

Menghasil software software yang terintergarsi dalam bidang elektromagnetik baik untuk pemodelan maupun pengolahan data

APLIKASI METODA ELEKTROMAGNETIK DAN GEOFISIKA LAINNYA PADA BEBERAPA KASUS YAITU : 1. BENCANA ALAM (GUNUNGAPI, KEGEMPAAN, LONGSOR) 2. GEOTHERMAL

18 8. USULAN BIAYA RISET 8.1 REKAPITULASI BIAYA : No. 1. 2. 3. 4. 5.

Keterangan

Dana

Belanja Pegawai Belanja Barang Honor Pihak Ke-3 Perjalanan Sewa alat, jasa layanan, dal lain lain

18.125.000,3.000.000,12.000.000,15.500.000,1.375.000,-

Jumlah

Rp 50.000.000,-

8.2 RINCIAN BIAYA : 8.2.1. Belanja pegawai No. 1. 2.

Pelaksana Kegiatan Peneliti Utama Anggota Peneliti

Jumlah Orang 1 2

Honor per Jumlah Jumlah Jam Jam/Bulan Bulan/Tahun 27.500 25 10 22.500 25 10 Jumlah total biaya honor (Rp)

Jumlah Biaya (Rp) 6.875.000,11.250.000,18.125.000,-

8.2.2. Belanja barang No. 1. 2.

Peralatan/Bahan

Biaya Satuan (Rp)

Jumlah Biaya (Rp)

2.000.000,-

2.000.000,-

1 SET 1.000.000,Jumlah total biaya barang (Rp)

1.000.000,3.000.000,-

Volume

Keperluan Survey (Accu, Peta, Batterai, dll) ATK

Satuan

1 SET

8.2.3. Belanja jasa a. Honor pihak ketiga non PNS ITB dan ITB-BHMN atau asisten mahasiswa Jumlah Honor per Jumlah Jumlah Jumlah Biaya No. Pelaksana Kegiatan Orang Jam Jam/Bulan Bulan/Tahun (Rp) 1. Mahasiswa 2 15.000,20 10 6.000.000,2. Tenaga penunjang 4 10.000,15 10 6.000.000,Jumlah total biaya honor (Rp) 12.000.000,b. Perjalanan No. 1.

2.

Jumlah Biaya (Rp) Survey untuk pengambilan data ke gunungapi, selama 15 hari dengan rincian : Tujuan

1.1 Sewa mobil (+bensin) 15 hari x Rp. 500.000 1.2 Akomodasi 4 orang x 15 hari x Rp. 100.000 Mengikuti Pertemuan Ilmiah nasional/internasional

Volume

Biaya Satuan (Rp)

15 hari

500.000,-

7.500.000,-

15 hari

400.000,-

6.000.000,-

2 orang

1.000.000,-

2.000.000,-

Jumlah total biaya perjalanan (Rp)

15.500.000,-

19 c. Sewa Alat, Jasa Layanan dan Lain-lain No. 1. 2.

Nama Alat/Jasa Layanan

Volume

Biaya Satuan (Rp)

Laporan dan Penggandaan 1 set 875.000,Rapat koordinasi 5x 100.000,Jumlah total biaya sewa alat, jasa layanan, dll. (Rp)

Jumlah Biaya (Rp) 875.000,500.000,1.375.000,-

II. Sarana

(1) Laboratorium Laboratorium Fisika Bumi ITB dilengkapi dengan peralatan penelitian yang lengkap untuk menunjang kegiatan penelitian ini.

(2) Peralatan utama: Peralatan utama yang dimiliki oleh Laboratorium Fisika Bumi adalah No. 1

2

Nama Alat

Kegunaan

CSAMT unit, GDP16 Untuk

pengukuran

Zonge

bawah permukaan

Sensor Magnetik

Untuk

Keterangan resistivitas

pengekuran

medan

magnetik 3

PC

Untuk pengolahan dan pemodeln numerik

III. Dukungan pada Pelaksanaan Penelitian Pada saat ini sudah disusun 2 buah makalah ilmiah Internasional dan 1 makalah Nasional yaitu : 1. Nurhasan , D. Sutarno, Y. Ogawa , N. Ujihara, S.B. Tank , Y. Honkura, Three Dimensional Electromagnetic Imaging of Kusatsu-Shirane Volcano and Its Implications for Hydrothermal System (submit to Geophysical Research Letter, 2010) 2. Nurhasan , D. Sutarno , Y. Ogawa , D. Sugiyanto , M Irwan, F. Kimata, Takeo Ito, Agustan, Investigation of Sumatra Fault based on Magnetotelluric and GPS Measurements (submit to Earth and Planetary Sciences Journal ) 3. Nurhasan , D. Sutarno, W. Srigutomo, E J Mustopa, U. Fauzi,Y. Ogawa, Three-Dimensional Resistivity Structure of Papandayan Volcano, Indonesia derived from Magnetotelluric Data (submit to Indonesian Physics Journal ) Ketiga makalah tersebut ditunjukan pada bagian lampiran :

20 9.

CV TIM PENELITI CURRICULUM VITAE

A. Personal Data 1. Name and title 2. Unit in ITB 3. Office address 4. Education Bachelor (S1) Master (S2) Doctor (S3) B. Position history 1999 – Now Sciences, ITB

: Nurhasan, Ph.D : Physics of Complex System, Faculty of Mathematics and Natural Sciences, ITB : Jl. Ganesha 10 Bandung 40132 : : Physics Department, Bandung Institute of Technology : Earth Science, Physics Department, Bandung Institute of Technology : Earth Sciences, Tokyo Institute of Technology, Japan (Electromagnetic induction for Volcano and Geothermal) : : Lecturer/Researcher at Faculty of Mathematics and Natural

Publications (International and Domestic) 4. Nurhasan , Y. Ogawa , N. Ujihara, S.B. Tank , Y. Honkura, S. Onizawa,, T. Mori , and M. Makino, 2006, Two electrical conductors beneath Kusatsu-Shirane volcano, Japan, imaged by audiomagnetotellurics and their implications for hydrothermal system, Earth Planets Space, vol. 53, 1053 - 1059. 5. Nurhasan , D. Sutarno, Y. Ogawa , N. Ujihara, S.B. Tank , Y. Honkura, Three Dimensional Electromagnetic Imaging of Kusatsu-Shirane Volcano and Its Implications for Hydrothermal System (submit to Geophysical Research Letter, 2010) 6. Hashimoto, T., T. Mogi, Y. Nishida, Y. Ogawa, N. Ujihara, M. Oikawa, M. Saito, Nurhasan, S. Mizuhashi, T. Wakabayashi, R. Yoshimura, A. W. Hurst, M. Utsugi, Y. Tanaka, Self-potential studies in volcanic areas (5) -Rishiri, Kusatsu-Shirane, and White Island-, J. Fac. Sci. Hokkaido Univ., Ser. VII, 12, 2, 97-113, 2004 7. Nurhasan, Y. Ogawa , N. Ujihara , S.B. Tank, T. Wakabayashi and S. Onizawa, Resistivity structure of Kusatsu-Shirane Volcano imaged by audio-magnetotelluric observations, Kusastu Report, 2004.10

International/Domestic Conferences 1. Nurhasan , Y. Ogawa, N. Ujihara , S.B. Tank , Y. Honkura , Teruo Yamawaki,

maging of Hydrothermal System in Kusatsu-Shirane Volcano, Japan, using Three Dimensional Magnetotelluric Inversion, The IAGA 11th Scientific Assembly, Sopron, August 23-30, 2009. 2. NURHASAN , D. Sutarno , Y. Ogawa , D. Sugiyanto , M Irwan, F. Kimata, Takeo

Ito, Agustan, Investigation of Sumatra Fault based on Magnetotelluric and GPS Measurements, The IAGA 11th Scientific Assembly, Sopron, August 23-30, 2009.

21 3. Nurhasan , D. Sutarno, W. Srigutomo, E J Mustopa, U. Fauzi,Y. Ogawa, ThreeDimensional Resistivity Structure of Papandayan Volcano, Indonesia derived from Magnetotelluric Data, Pertemuan Ilmiah Tahunan Himpunan Ahli Geofisika Indonesia (PIT HAGI), Yogyakarta, 9 – 12 November 2009 4. Nurhasan , D. Sutarno, Y. Ogawa, Dimensionality Analysis of Resistivity Structure of Volcanic Zone from Magnetotelluric Data, Pertemuan Ilmiah Tahunan Himpunan Ahli Geofisika Indonesia (PIT HAGI), Yogyakarta, 9 – 12 November 2009.Geomagnetism Meeting, Tokyo, 2009 5. Y. Ogawa , Nurhasan, S.B. Tank, N. Ujihara, Y. Honkura, & T. Yamawaki , Imaging a Vapor Reservoir at Kusatsu-Shirane Volcano, By Three-Dimensional MT Inversion and Relocated Micro-Earthquakes, Geomagnetism Meeting, Tokyo, 2009 6. Enjang J M, Nurhasan , Doddy Sutarno, Wahyu Srigutomo, Two-dimensional Electromagnetic Image of Kamojang Geothermal Field, Indonesia by CSAMT Data, ( accepted to be presented on 19th electromagnetic induction workshop, Beijing , China, 23 – 29 October 2008) 7. Nurhasan , Y. Ogawa , Doddy Sutarno, Didik Sugiyanto, Imaging fault zone by MT Method at Sumatra area in Indonesia ( accepted to be presented on 19th electromagnetic induction workshop, Beijing , China, 23 – 29 October 2008) 8. Nurhasan , Y. Ogawa , N. Ujihara, S.B. Tank , Y. Honkura, Geothermal system of a phreatic eruption environment under Kusatsu-Shirane volcano, implied by three dimensional magnetotelluric modeling, IUGG Meeting, Perugia, Italy, 2 – 13 July, 2007 9. Mogi T, Nurhasan, Y. Ogawa, Djedi, W.S , Resistivity structure at damage area of the 2006 mid Java earthquake, IUGG Meeting, Perugia, Italy, 2 – 13 July, 2007 10. Nurhasan , Y. Ogawa , N. Ujihara, S.B. Tank , Y. Honkura, Three-dimensional electromagnetic image of Kusastu-Shirane volcano and its implications for hydrothermal system, 18th induction workshop, Barcelona , Spain, 2006.9.17-23. 11. Kasaya, K, Y. Ogawa, Nurhasan, N. Ujihara, F. Kimata, Fluid detection using AMT survey on the seismogenic zone around the eastern foot of Mt. Ontake, central Japan, IAGA General Assembly, Toulouse, France, 2005.7.18-29 12. Ogawa, Y, Nurhasan, N. Ujihara, S. Onizawa, Electromagnetic imaging of seismic LP resonator at Kusatsu-Shirane volcano, Japan, IAGA General Assembly, Toulouse, France, 2005.7.18-29 13. Nurhasan , Y. Ogawa , N. Ujihara , S.B. Tank, and S. Onizawa, Kusatsu-Shirane volcano imaged by audio magnetotelluric method, 17th induction workshop, Hyderabad, India, 2004.10. 14. Ogawa, Y, M. Uyeshima, Nurhasan, K. Takahashi, S. Koyama, T. Ogawa, Weerachai Siripunvaraporn, R. Yoshimura, H. Satoh, Magnetotelluric evidence for groundwater loss as a cause of continuous SO2 degassing at Miyakejima volcano, Japan, 17th induction workshop, Hyderabad, India, 2004.10. 15. Nurhasan,Yasuo Ogawa, Naoto Ujihara, Electromagnetic images of KusatsuShirane volcano and its implications for hydrothermal system, Conductive Anomaly Meeting, University of Tokyo, Japan, December 2005. 16. Nurhasan ,Yasuo Ogawa, Naoto Ujihara, Electromagnetic Image of seismic LP resonator at Kusatsu-Shirane volcano, Volcano Meeting 、 Sapporo, Japan, October 2005 17. Nurhasan , Yasuo Ogawa, Naoto Ujihara, Onizawa Shinya, Audiomagnetotelluric

22 study of the geothermal system of Kusatsu-Shirane volcano, Geomagnetism Meeting, Kyoto, Japan, September 2005.

Research project activities: No.

Research / Project

Year

Position

1

Pengembangan Pemodelan Elektromagnetik ”Audio Magnetotelluric” Tiga Dimensi sebagai Sarana Informasi Alternatif untuk Monitoring Gunungapi , PROGRAM INSENTIF RISET DASAR, KNRT. Image of subduction zone in Aceh region, Sumatra, Indonesia using magnetotelluric method, Joint research Unsyiah – ITB - Tokyo Institute of Technology, Japan Repeating magnetotelluric measurement in Kusatsu-Shirane volcano, Japan and its implication to geothermal system, Visiting Researcher at Tokyo Institute of Technology, Japan Electromagnetic study in Bantul-Yogyakarta to delineate shallow soft sediment and its implication in earthquake distribution, Joint research LIPI – Hokkaido University EARTH : How to build habitable planets ?, part of The 21st Century CEO Program, Tokyo Institute of Technology, Japan

2008 2009

Principal investigator

2008 2009

Researcher

2007

Researcher

2006

Member

2005

Research Assistant

2

3

4

3

Bandung, 30 September 2010

Dr. NURHASAN

23

CURRICULUM VITAE 1.

Name

:

2.

Place and date birth :

Bandung, January 9, 1953

3.

Current Position

Lecturer/Researcher

:

Doddy Sutarno, Ph. D.

4.

Educational experience: 1992 Ph. D. (in Geophysics) from Macquarie University, Sydney, NSW, Australia. 1983 M.Si. (in physics) from Bandung Institute of Technology, Bandung. 1979 Sarjana (in physics) from Bandung Institute of Technology, Bandung 5.

Research experience: No

Project Name

Period

Position

1

Proyek DIP-ITB: Penyelidikan Air Tanah dengan Metoda “Geoelectrics Plurry direction” di Daerah Gunung Kidul, Jawa Tengah

1981-1982

Angggota

2

Proyek DIP-ITB: Penentuan Elastisitas Campuran Bahan Padat dengan Gelombang Ultra Sonic

1982-1983

Ketua

3

Proyek DPPM: Pemodelan Konduktivitas Batuan Berdasarkan Teori Perkolasi

1982-1983

Anggota

4

Proyek DIP-ITB: Aplikasi Data Seismogram Gempa Bumi untuk Studi Regional

1983-1984

Anggota

5

Proyek PPPG: Penyelidikan Gaya Berat dan Geolistrik secara terpadu di Daerah Cimareme

1983-1984

Anggota

6

Proyek DPPM: Penelitian Chemisorpsi Logam

1984-1985

Anggota

7

Proyek DPPM: Pengembangan Metoda Polarisasi Terimbas dan TURAM

1984-1985

Ketua

8

Seismic survey at Mora, Western Australia.

1987

Anggota

24 9

CSAMT Survey at Queenstown, Tasmania

1988

Anggota

10

MT survey at north Melbourne, Australia

1989

Anggota

11

Proyek OPF-ITB: Pengembangan Metoda Seismik Refraksi Vertikal

1992-1993

Ketua

12

Proyek Penelitian Basic Science I: Inversi Magnetotelurik 2-D

1992-1993

Ketua

13

Proyek Penelitian Basic Science II: Pemodelan Elemen Hingga Magnetotelurik 2-D

1993-1994

Ketua

14

Proyek Penelitian Basic Science III: Pemodelan Magnetotelurik 2-D dengan Metode Persamaan Integral

1994-1995

Ketua

15

Riset Unggulan Terpadu I: Studi Evolusi Tektonik dengan Metoda Geofisika Terpadu untuk Menyelidiki Potensi Sumber Alam di Daerah Lengguru, Irian Jaya

1993-1996

Anggota

16

Riset Unggulan Terpadu III: Penyelkidikan Sungai Bawah Tanah dengan Metoda Elektromagnetik-VLF dan Gaya berat di Daerah Gunung Kidul, Jawa Tengah

1995-1998

Anggota

17

Riset Unggulan Terpadu (RUT) VI: Aplikasi Teknologi Elektromagnetik dan Simulasi Numerik dalam Pengembangan Energi Gunung Api Sebagai Wahana Energi Alternatif di Masa Mendatang

1998-2001

Ketua

18

Hibah Bersaing X: Aplikasi Metoda CSAMT untuk Monitoring Aktivitas Gunung Api

2002-2003

Anggota

19

Program Riset ITB: Estimasi robust Fungsi IMPedansi CSAMT berdasarkan estimator-M

2006-2007

Ketua

20

Proyek Riset KK- ITB: Estimasi robust Fungsi IMPedansi CSAMT berdasarkan estimator-M TAHAP II

2007-2008

Ketua

2007-2009

Anggota

21 Program Intensif Riset Terapan-KNRT: Aplikasi teknologi elektromagnetik “Controlled Source Audio Magnetotelluric (CSAMT)” untuk

25 Eksplorasi Panas Bumi Sebagai Sumber Energi Alternatif

6. Selected publications and presentations Sutarno, D. (2010) Robust Magnetotelluric Impedance Estimation, Accepted for The 4th Asian Physics Symposium, Bandung, Indonesia. Nurhasan, D. Sutarno, W. Srigutomo, E.J. Mustopa, U. Fauzi, Y. Ogawa (2009). Three Dimensional Resistivity Structure of Papandayan Volcano, Indonesia derived from Magnetotelluric Data, The 34th HAGI Annual Convention, Exhibition and 2nd Geophysics Education Symposium Yogyakarta, November 2009. Nurhasan, D. Sutarno, Y. Ogawa (2009). Pendugaan Struktur Resistivitas Cekungan Bandung Bagian Timur, Menggunakan Metode CSAMT Pendekatan Gelombang Bidang, The 34th HAGI Annual Convention, Exhibition and 2nd Geophysics Education Symposium Yogyakarta, November 2009. Harja, A., W. Srigutomo2, E.J. Mustofa,D. Sutarno (2009). Pendugaan Struktur Resistivitas Cekungan Bandung Bagian Timur, Menggunakan Metode CSAMT Pendekatan Gelombang Bidang, The 34th HAGI Annual Convention, Exhibition and 2nd Geophysics Education Symposium Yogyakarta, November 2009. Sutarno, D. (2008). Constrained robust estimation of magnetotelluric impedance functions based on a bounded-influence regression M-estimator and the Hilbert transform, Nonlinear Processes in Geophysics, 15, 287-293. Sutarno, D. and I. Fatrio (2007). Robust M-estimation of CSAMT impedance functions, Indonesian Journal of Physics, 18:3, 81-85 Sutarno, D. and Fatrio, I. (2007) An application of Robust M-Estimation to CSAMT Data Processing, Proceeding of the 11th SEGJ Conference, Sapporo, Japan. Sutarno, D. and I. Fatrio (2007). An Application of robust M-estimation with the Hilbert transform to CSAMT data processing, Proc. of The 2nd Asian Physics Symposium, Bandung Indonesia. Sutarno, D., (2006). Development of Robust Magnetotelluric Impedance Estimation, Indonesian Journal of Physics, 16, no. 3, 81 - 91 Sutarno, D., (2006). Robust estimation of magnetotelluric impedance functions based on a bounded-influence regression M-estimator and the Hilbert transform, Geophysical Research Abstracts, 8, 01612 (Presented in EGU General Assembly, Vienna). Sutarno, D. (2006). Robust estimation of magnetotelluric impedance functions based on the regression M-estimator, in “ Geo-hazard and earth-resources in Indonesia”, Geoforum Bandung V, HAGI. Fatrio, I., and Sutarno, D. (2006). Robust M-estimation of Controlled Source Audio Magnetotellurics (CSAMT) Impedance Functions, Proceeding of the International Conference on Mathematics and Natural Sciences, ISBN:979-3507-91-8, 862-865 Harja, A., Sutarno, D., and Srigutomo, W. (2006). DC-resistivity survey for groundwater investigation: Case Study in Eastern Bandung, Proceeding of the International Conference on Mathematics and Natural Sciences, ISBN:979-3507-91-8, 12811283 Srigutomo, W., A. Harja, D. Sutarno, and T. Kagiyama (2006). VLF data analysis through transformation into resistivity value: application to synthetic and field data, Indonesian Journal of Physics, 16:4, 83-95

26 Srigutomo, W., Sutarno, D. and Harja, A. (2006). 2-D Magnetotellurics numerical modeling using the boundary element method, , Proceeding of the International Conference on Mathematics and Natural Sciences, ISBN:979-3507-91-8, 965-968 Sutarno, D. (2005). Phase-smoothed Robust Estimation of Magnetotelluric impedance Functions Based on A Bounded-influence Regression M-estimator, Jurnal Geofisika, 4, no. 2, 10-16.

Bandung, September 30, 2010

Prof. Doddy Sutarno, Ph.D.

27

Nama : Dr. rer. nat. Sparisoma Viridi Tempat / Tanggal Lahir : Jakarta / 1 Desember 1973 Pengalaman riset Pemberi Dana Ikatan Alumni Institut Teknologi Bandung

Tempat Fakultas Matematika dan Ilmu Pengetahuan Alam, Institut Teknologi Bandung

Direktorat Pendidikan Institut Teknologi Bandung Riset Kelompok Keahlian Institut Teknologi Bandung

Fakultas Matematika dan Ilmu Pengetahuan Alam, Institut Teknologi Bandung Fakultas Matematika dan Ilmu Pengetahuan Alam, Institut Teknologi Bandung

Ikatan Alumni Institut Teknologi Bandung

Fakultas Matematika dan Ilmu Pengetahuan Alam, Institut Teknologi Bandung Fakultas Matematika dan Ilmu Pengetahuan Alam, Institut Teknologi Bandung

Institut Teknologi Bandung

Quality for Undergraduate Education (QUE) Project Nomor riset 20920202 DIKS ITB, LPPM ITB

Departemen Fisika, Fakultas Matematika dan Ilmu Pengetahuan Alam, Institut Teknologi Bandung Departemen Fisika, Fakultas Matematika dan Ilmu Pengetahuan Alam, Institut Teknologi Bandung

Judul Riset Brazil-nut effect and its reverse in two dimension: registering transition parameters using molekular dynamics and building a simple model Evaluasi sekunder tematik matakuliah Fisika Dasar

Tahun 2009

Penyeleksian molekuler secara mekanika kuantum terhadap klorofil dan senyawa turunannya berdasarkan sifat optoelektronik dalam pemanfaatan sebagai sel surya organik Modelling granular oscillation induced by chaos using flux equation and neuratl network Pemodelan ion dalam kisi kubik sederhana dalam pengaruh medan magnetik luar Piranti lunak semi intepreter untuk membantu kuliah Fisika Matematika

2008

Belajar probabilitas dan statistika dasar dengan bantuan halaman web

2002

Publikasi terkini yang terkait 1. Suparno Satira, dan Sparisoma Viridi, "Mekanisme Penyusulan Molekul Antibodi dalam Larutan Sodium Alginat", Jurnal Nanosains dan Nanoteknologi, Edisi Khusus Agustus, 109111 (2009) 2. Sparisoma Viridi, Suparno Satira, and Freddy P. Zen, "Energy dissipation as function of vibration frequency for monodispersed granular particles in two chamber system", Proceeding of Conference on Mathematics and Natural Sciences 2008, Bandung, 28-30 Oktober 2008, Indonesia 3. Sparisoma Viridi, Patrick Grete, and Mario Markus, “A minimal mechanical device displaying ‘bona fide’ stochastic resonance”, Physics Letters A 372 (2008) 1040-1043 4. Sparisoma Viridi, Cooperation between dynamic coefficient of restitution and density ratio in supporting granular gas oscillation occurrence, Indonesian Journal of Physics 18 (4) (2007) 103-105

2009

2008

2003

2003

28 5. Sparisoma Viridi, A few granular materials in two horizontal chambers system, Proceedings of the 2007 Asian Physics Symposium (APS 2007), November 29 – 30, 2007, Bandung, Indonesia, A.21 (2007) 6. Sparisoma Viridi, Malte Schmick, and Mario Markus, Experimental observations of oscillations and segregation in a binary granular mixture, Physical Review E 74, 041301 (2006) 7. Sparisoma Viridi, Malte Schmick, and Mario Markus, "Granular clock" and full segregation in a shaken, binary granular medium: experiments and simulations, Nonlinear Phenomena in Complex Systems 9,352 (2006)

Bandung, September 30, 2010

Dr.rer.nat. Sparisoma Viridi

29

LAMPIRAN BUKTI CAPAIAN OUTPUT TAHUN 2009-2010 MAKALAH 1 : SUBMIT TO Geophysical Research Letter (Int. Journal), 2010

Three Dimensional Electromagnetic Imaging of Kusatsu-Shirane Volcano and Its Implications for Hydrothermal System Nurhasan1 , Y. Ogawa2,3 , N. Ujihara2 , S.B. Tank4 , Y. Honkura2 1 Physics Department, Bandung Institute of Technology, Bandung, Indonesia 2 Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo, Japan 3 Volcanic Fluid Research Center, Tokyo Institute of Technology, Tokyo, Japan 4 Kandilli Observatory and Earthquake Research Institute, Boğaziçi University, İstanbul, Turkey

Abstract Three-dimensional resistivity structure of Kusatsu-Shirane volcano was imaged by the dense magnetotelluric measurements (83 sites) using 3D inversion. To overcome the effect of shallow three dimensional structure or galvanic distortion, We have also developed the new methodology of modeling by applying phase tensor and induction vector as response functions in the 3d forward modeling. The three-dimensional topography was also taken into account in the modeling and twodimensional inversion results of multiple profiles were used as the initial three-dimensional model. Based on the final 3d resistivity model, a 200-500 m thickness disk-shaped conductive zone was observed in the center of the model beneath the crater. Interpreting conductor as clay cap of hydrothermal system, important information was obtained indicating that two phase reservoir is located in the high resistivity zone just beneath the clay cap corresponding to high temperature region. On the other hand, deeper structure is characterized by a simple two-dimensional structure with N-S strike, i.e., the 1km-wide central resistive gap associated with break down of clay mineral because of high temperature. 1. Introduction Kusatsu Shirane volcano is an active volcano located in central of Japan. This volcano situated at the south edge of South-East Acr. Geologically, Kusatsu Shirane volcano was covered by pyroclastic cone in the summit area surrounded by lava flow around the summit area [Uto et al., 1983]. Some evidences such as hot spring, vent and

hydrothermal manifestation shown that hydrothermal system plays an important role in this volcano. . Magnetotelluric method as one of the electromagnetic methods is the most popular method for detecting the presence of fluids and clay minerals in the hydrothermal system. Application of magnetotelluric method can be found at active volcanoes [Ogawa and Takakura, 1990; Ogawa et al., 1992, 1998, 1999; DiMaio et al., 1998; Kagiyama et al., 1999; Fuji-ta et al, 1999; Matsushima et al., 2001; Muller and Haak, 2004; Manzella et al., 2004; Aizawa et al., 2005], hydrothermal systems [Oskooi et al., 2005; Pellerin et al., 1996; Caglar and Isseven, 2004], and active faults [Unsworth, et al., 1999; Tank, et al., 2003]. In developing a methodology of modeling, 3-D modeling of magnetotelluric data has been developed based on using a non free distortion parameter such as apparent resistivity [Mogi, 1996; Siripunvaraporn et al., 2000; Sasaki, 2001; Shi et al., 2004]. Muller et al. [2004] have applied geomagnetic induction vector to examine lateral variation of resistivity distribution in volcano region with a small number of site. Our motivation was inspirited by the fact that the existence of small local 3d structure will result a misinterpretation of final results. Therefore, use of non free distortion parameter is not useful to remove effect of small 3d structure. Earlier method applied to reduce effect of 3d small structure such as Groom-Bailey decomposition [Groom and Bailey, 1989] and Bahr methods [Bahr, 1991] were developed. Their methods limited to only twodimensional regional structure because of the use of non-free distortion parameter such as apparent resistivity. In 2004, Caldwell et al. [2004] introduced phase tensor as a parameter which is not

30

138.5400

138.5450

026 029

36.6500

021

020

032

023

20 20

AMT (Audiomagnetotelluric) and Magnetotelluric data were collected in the summit area in different campaigns from 2001 to 2005. For the measurements, we used two sets of Phoenix Geophysics MTU5A system to measure electric and magnetic fields. AMT measurements was recording up to five components of electromagnetic fields (two horizontal electric fields, two horizontal magnetic fields and vertical magnetic field) in the frequency range of 1Hz to 1 kHz. On the other hand, MT survey measured electric fields at each site but used magnetic fields at base stations to calculate impedances. Thus, the MT sites have no information on the magnetic transfer functions. Moreover, the MT data are available only in a limited frequency range below 320Hz down to 0.01Hz. The remote reference technique was also applied to reduce the noise contamination. The measurement at each site took an hour to several hours. These differences in the two datasets should be noted for the compilation. In total, after the compilations, there are total of 85 sites involving AMT and MT data with a spacing of approximately 200m covering the peak area encircling the Mizugama and Yugama craters (See Figure 1).

138.5350

033

025

038

047

018

062

079

078 075 022 061

36.646

067

0

068

069

017

006 073

058

066

057 037

012

056 076

074

085

035

0

200

400

084

031

011

065 20

Meter

013

044

054 053

003 045

064 052

083 082

600

004

055

008

20

036

36.6380

042

015

028

36.6420

041

059

077

040

034

024

060

071 009 072

070

030

039

005

016

043

2140

Latitude

019

AMT Sites 081

051

027

007

0

2.1. Data Acquisition

138.5300

8 19

2. Data Acquisition and Observed Data

Longitude 138.5250

2060

affected by distortion caused by shallow 3d structure. In this paper, we applied response functions namely phase tensor and induction vector that are free distortion effect to 3d forward modeling. We use natural electromagnetic fields in the frequency range between 10 kHz to 0.3Hz. The resistivity model will be interpreted with the aids of other known information, such as drill-hole data [Kurasawa, 1993]. During period of 1990s, some peculiar phenomena were observed indicating increase of seismic activity [Nakano et al, 2003] and polarization of change of total magnetic force in N-S direction [Yamazaki, et. al, 1992]. These phenomena correspond to enhancement of volcano activity because of hot fluid activity beneath the summit area. Other observations, such as geochemical studies [Hirabayashi et al., 1997; Ohba et al., 1994, 200, 2002; Ohwada et al., 2003; Ossaka et al., 2005], gravity studies [Makino et al., 2004], and LongPeriod event studies [Nakano et al., 2003] were undertaken in this volcano. However, none of these gave quantitative image of the whole geothermal system of the volcano. The objective of our research is to get the detail image of hydrothermal system in terms of resistivity structure and how its relationship to hot fluid flow to explain mechanism of hydrothermal system in this volcano.

010

001

050

080

X

Seismicity

MT Sites

High temperature zone

LP resona tor

Demagnetization source

063

Figure 1. MT and AMT site locations 2.2. Presentation of the observed Data Different from plotting of phase tensor defined by Caldwell et al. [2004], in this paper, we calculated the arctangent of the YYcomponent of the phase tensor as a function of the coordinate angles (X direction of the rotated frame) by with 3 degree steps. For the modeling and analysis, we have applied three representative frequencies (1, 10, and 100 Hz) by reason that these frequencies correspond to the skin depth of our target. Figure 2 shows observed phase tensor and induction vector used to analyze dimensionality of the structure. For the frequency of 100 Hz, the observed phase tensors are dominated by elliptic phase tensors rather than circular phase tensors where alignment of major axes are distributed spatially inconsistently reflecting the heterogeneous structure at the corresponding skin depth. The induction vectors generally point toward the central area, but they also indicate directional variations reflecting the existence of some other local conductive anomalies.

Figure 2. Observed data in Phase Tensor and Induction Vector representations. On the other hand, at 10Hz, the phase tensors and the induction vectors show clearly the circular anomalous structure around summit area. The existence of 3-D conductive zone at the shallow part provides an explanation for the

31 consistent directions of the induction vectors. Evidence of the three-dimensionality around the summit of Kusatsu-Shirane volcano is also detected by gravity observation [Makino et al., 2004]. At the frequency of 1 Hz representing deeper structure, two-dimensionality is very dominant as exhibited by phase tensors and induction vectors. Dominant alignment of the long axis of the ellipse with the east-west direction and the eastward induction vectors indicate that the existence of two-dimensional structure with N-S strike.

Figure 3. Final model of resistivity distribution obtained from 3D inversion. 3. 3-D Inversion 3-D inversion’s code providing by Wiraacahi was used to invert overall MT data with a total of 85 sounding. The 7 representative frequencies were used in this inversion starting from 0.1 To 100 Hz. The earth model is divided into rectangular blocks with magnetic field H defines along the block edge. In this procedures of 3-D modeling process, the total area of the model 6 km x 6 km x 10 km are divided into 38 x 44 x 30 grids in x,y,z direction, respectively with air mesh consist of 7 layers. Distances between grids are made logarithmically increased starting from the center of the model. Homogeneous model was used for the initial model and the resistivity of Yugama lake water is set to 0.3 m based on the measurement of lake water samples.

4. Result and Interpretation Based on the final 3-D model shown in Figure 3, the summit area is characterized by an additional shallow complexity, compared with the deeper two-dimensional structure. Surface structure is dominated by high resistivity of 10k Ω.m at the eastern part of summit and 100 Ω.m at the western part of the summit area. This structure agrees with distribution of lava in geological structure. Small two conductors (C0b and C0c in Figure 3) exposed to the surface coincidence with the locations of the vents and hydrothermal manifestations.

The main structure of the clay cap of hydrothermal system was found in the center of the model at the depth of 200 – 700 m from the surface (C0a in Figure 4). This conductor ranging of 1- 5 Ω.m was forming an elliptic conductive cap with major axes of 2 km aligning in north-south direction. The existence of this conductor is clearly detected by the induction vectors at frequencies 100Hz and 10 Hz, which point toward the center of the model. This conductor is interpreted as a clay cap. Between the depths of 400 – 700 m from the surface, there is a significantly resistive zone under Mizugama crater. In another word, the thickness of the clay cap is significantly reduced as 200m, compared with the surroundings. In the deep structure, the 3-D final model consists of the two parallel conductive blocks (C1 and C2) in a 100 Ω.m homogeneous media where western conductive block is slightly deeper than the eastern one. This is also supported by the twodimensional inversion results from multiple profiles. The resistive gap between deep two conductive blocks between C1 and C2 is important feature because it is located just beneath ellipseshaped clay cap. The loss of high conductivity in this zone implies that the conductive clay cannot exist as the temperature is significantly higher than 200oC.

Figure 4. The section located in the middle of the final model.

32 5. Discussion It has been believed that hydrothermal system plays an important role under KusatsuShirane volcano associated with volcano activity [Hirabayashi, 1999, Ohba et al., 2002, Nakano et al., 2003, Kumagai et al., 2003, Yamazaki et al., 1992]. Some evidences such as hydrothermal surface manifestation and clay mineral ejected from eruption were observed in this volcano. Figure 4 shows resistivity structure, which is cut from the 3D model corresponding to the profile located at the center of the model in west-east direction where the thinner clay mineral takes place. Interpretation of a 500 m thickness disk-shaped conductor (C0) located in the center of the model as a clay mineral is supported by drillhole data provided by Kurasawa, [1993]. He has reported that The smectite rich zone was detected below the 1500m a.s.l and chlorite zone is detected beneath the smectite zone. Mapping of the low resistive zone as clay cap (C0 and C1) provides an information of 2000 C isotherms as the bottom of the conductor. Therefore, high temperature zone should exist in resistive zone beneath the clay cap. The location and the size of C0 clay cap coincide with the existence of the low density material inferred from low gravity anomaly [Makino et al., 2004]. A resistive block with size 1 km x 200 m x 200m, capped with the thin C0 conductor is found at the east of Mizugama crater where LP resonator is located. Nakano et al. [2003] pointed out that the LP resonator can be a hydrothermal reservoir hosting fluids and gases in the horizontal cracks. In our model, the LP resonator is just the top part of the geothermal system, capped by the impermeable clay. The gravity analyses in association with the resistivity distribution of regional profiling showed that the western conductor is in the basement, but the eastern one is above the basement [Nurhasan et al., 2006]. In this profile 4, we have re-plotted the gravity basement overlaid on the resistivity structure. Geologically, the eastern conductor implies alteration zone in PliocenePleistocene formation while the western conductor implies alteration zone Miocene formation. This can explain the different thickness of these conductors where western conductor is slightly deeper that eastern conductor. The temporal magnetization study has the equivalent dipole location in the resistive zone 900m from the surface under Mizugama crater [Yamazaki et al., 1992]. The thermal demagnetization can be caused by heating process of the volcano where high temperature (the temperature does not have to reach the Currie temperature) is considered. They have found that source of demagnetization is located east of Mizugama crater at the depth of about 900m from the surface which corresponds to the Currie temperature of 5500 C if it is totally demagnetized.

The equivalent dipole locations is in the resistive zone below the clay cap where higher temperature than 200oC is expected. Thus our isotherm of 200oC as the bottom of the conductor is consistent with the geotherm inferred from demagnetization [Yamazaki et al., 1992]. The western deep conductor (C2) in this area can be interpreted either as fluids or clay minerals. There is no helpful information for the implications of the west conductor such as logging information. One of the possible interpretations is the existence of the hot saline fluid which has an important role in earthquake generation as detected near this conductor. The existence of the saline fluid in the porous media can be a candidate to decrease the bulk resistivity of the rocks. However, both deep conductors have comparable depth which means that the interpretation of them should be not much different. Moreover the existence of the seismicity is distributed along the gap between these conductors indicating that not only west conductor contribute to the earthquake generation but also another one. Although many papers point out the relationship between earthquake distribution and resistivity distribution [Ogawa et al., 2001; Tank et al., 2003; Kasaya et al., 2002]. Ogawa et al. [2001] pointed out that the seismic activities have a strong correlation to low resistivity zone as a sequence of the trapped free water that discharges from deeper level. Kasaya et al. [2002] have observed the deep conductor at Mt. Ontake region and the coincidence to the cutoff depth of the seismicity. They concluded that the trapped free water in the brittle-ductile transition zone is the cause of the earthquake generation. Such interpretation may also be applicable to the western deep conductor and the clustering of the earthquake near the eastern edge of the western conductor. As we seen in the 3-D final model, both deep conductors are widely spreading in southnorth direction and hence the more possible interpretation is clay mineral for west deep conductor rather than fluids. 6. Conclusion In summary, we have thus successfully modeled the three-dimensional resistivity structure using 3D inversion where distortion-free response functions such as phase tensors and induction vectors were used for fitting the data. Moreover, we investigated the underlying geothermal structure which was only qualitatively known. The key of the interpretation was the smectite, which is electrically conductive and hydrologically impermeable. Also underlying thermal structure was inferred using the bottom of the conductor as a proxy for 200oC isotherm as the smectite breaks down above the temperature.

33 References Aizawa, K., R. Yoshimura, N. Oshiman, K. Yamazaki, T. Uto, Y. Ogawa, S.B. Tank, W. Kanda, S. Sakanaka, Y. Furukawa, T. Hashimoto, M. Uyeshima, T. Ogawa, I. Shiozaki, and A. Hurst (2005), Hydrothermal System beneath Mt. Fuji volcano inferred from Magnetotellurics and Electric Selfpotential, Earth Planet. Sci. Lett., 235, 343355. Bahr, K. (1991), Geological noise in magnetotelluric data : a classification of distortion types. Phys. Earth Planet. Inter., 66, 24-38. Çaglar, I., and T. Isseven (2004), Two-dimensional geoelectrical structure of the Göynük geothermal area, northwest Anatolia, Turkey, J. Volcano. Geotherm. Res., 134, 183-197. Caldwell, T.G., H.M. Bibby, and C. Brown (2004), The magnetotelluric phase tensor, Geophys. J. Int., 158, 457 – 469. Di Maio, R., P. Mauriello, D. Patella, Z. Petrillo, S. Piscitelli, S. and A. Siniscalchi (1998), Electric and electromagnetic outline of the Mount Somma–Vesuvius structural setting, J. Volcano. Geotherm. Res., 82, 219-238. Fuji-ta, K., Y. Ogawa, M. Ichiki, S. Yamaguchi, and Y. Makino (1999), Audio frequency magnetotelluric survey of Norikura Volcano in central Japan, J. Volcano. Geotherm. Res., 90, 209217. Groom, R. W. and R.C. Bailey (1989), Decomposition of magnetotelluric impedance tensor in the presence of local threedimensional galvanic distortion, J. Geophys. Res., 94, 1913–1925. Hirabayashi, J., T. Ohba, and K. Nogami (1997), Hydrothermal system of Kusatsu-Shirane volcano and Kirishima volcanic area inferred from geochemical observations, 53-62, proceedings on magma prospecting present and future perspective, Sakurajima volcano observatory, Kyoto University(in Japanese with English abstract). Hirabayashi, J. (1999), Formation of volcanic fluid reservoir and volcanic activity. J. Balneol. Soc. Jpn., 49, 99-105 (in Japanese with English Abstract). Kagiyama, T., H. Utada, and T. Yamamoto (1999), Magma ascent beneath Unzen Volcano, SW Japan, deduced from the electrical resistivity structure, J. Volcano. Geotherm. Res., 89, 3542. Kasaya, T., N. Oshiman, N. Sumitomo, M. Uyeshima, Y. Iio, and D. Uehara (2002), Resistivity structure around the hypocentral area of the 1984 Western Nagano Prefecture

earthquake in central Japan, Earth Planets Space, 54, 107-118. Kumagai, H., B.A. Chouet, and M. Nakano (2002), Temporal evolution of a hydrothermal system in Kusatsu-Shirane Volcano, Japan, inferred from the complex frequencies of long-period events, J. Geophys. Res., 107(B10), 2236, doi:10.1029/2001JB000653. Kurasawa, T. (1993), Problem with the drilling of geothermal well in the south of Mt. KusatsuShirane, Gunma Prf., J. Japan Geothermal Energy Assoc., 30, 1-23(in Japanese with English Abstract). Mackie, R.L., Madden, T.R. and Wannamaker, P.E. (1993), Three-dimensional magnetotelluric modeling using finite difference equations – Theory and comparisons to integral equation solutions: Geophysics, 58, 215-226. Makino, M., S. Watanabe, T. Sumita, and Y. Ogawa (2004), Microgravity Survey in the vicinity of the Kusatsu－Shirane Summit, Report on the 4th joint observation of Kusatsu-Shirane volcano, 69-80(in Japanese). Manzella, A., G. Volpi, A. Zaja, and M. Meju (2004), Combined TEM-MT investigation of shallow-depth resistivity structure of Mt Somma-Vesuvius, J. Volcano. Geotherm. Res., 131, 19-32. Matsushima N., H. Oshima, Y. Ogawa, S. Takakura, H. Satoh, M. Utsugi, and Y. Nishida (2001), Magma prospecting in Usu volcano, Hokkaido, Japan, using magnetotelluric soundings, J. Volcano. Geotherm. Res., 109 (4), 263-277. Mogi, T. (1996), Three-dimensional modeling of magnetotelluric data using finite element method, J. of Applied Geophys, 38, 185-189. Muller A, and V. Haak (2004), 3-D modeling of the deep electrical conductivity of Merapi volcano (Central Java): integrating magnetotellurics, induction vectors and the effects of steep topography, J. Volcano. Geotherm. Res., 138 (3-4): 205-222.

Nakano, M., H. Kumagai, and B.A., Chouet (2003), Source mechanism of long-period events at KusatsuShirane Volcano, Japan, inferred from waveform inversion of the effective excitation functions, J. Volcanol. Geotherm. Res., 122, 149164. Nurhasan , Y. Ogawa , N. Ujihara, S.B. Tank , Y. Honkura, S. Onizawa,, T. Mori , and M. Makino (2006), Two electrical conductors beneath

34 Kusatsu-Shirane volcano, Japan, imaged by audiomagnetotellurics and their implications for hydrothermal system, Earth Planets Space, 58, 1053 – 1059. Ogawa, Y., S. Takakura, and Y. Honkura (2002), Resistivity structure across Itoigawa-Shizuoka tectonic line and its implications for concentrated deformation, Earth Planets Space, 54, 1115-1120. Ogawa, Y., M. Mishina, T. Goto, H. Satoh, N. Oshiman, T. Kayasa, Y. Takahashi, T. Nisitani, S. Sakanaka, M. Uyeshima, Y. Takahashi, Y. Honkura, and M. Matsushima (2001), Magnetotelluric imaging of fluid in the interpolate earthquake zone, NE Japan back arc, Geophys. Res. Lett., 28, 3741-3744. Ogawa, Y., H.M. Bibby, T.G. Caldwell, S. Takakura, T. Uchida, N. Matsushima, S.L. Bennie, T. Tosha, and Y. Nishi (1999), Wide-band Magnetotelluric Measurements across the Taupo Volcanic Zone, New Zealand Preliminary Results, Geophys. Res. Lett., 26, 3673-3676. Ogawa, Y., N. Matsushima, H. Oshima, S. Takakura, M. Utsugi, K. Hirano, M. Igarashi, and T. Doi (1998), A resistivity cross-section of Usu volcano, Hokkaido, Japan, by audiomagnetotellurics soundings, Earth Planets Space, 50, 339-346. Ogawa, Y. and T. Uchida (1996), A two-dimensional magnetotelluric inversion assuming Gaussian static shift, Geophys. J. Int., 126, 69–76. Ogawa, Y., S. Takakura, and T. Soya (1992), Wideband magnetotelluric measurements across Izu-Oshima volcano, J.Geomag.Geoelectr., 44, 561-566. Ogawa, Y., and S. Takakura (1990), CSAMT measurement across the 1986 C Craters of Izu-Oshima Island, Japan, J.Geomag.Geoelectr., 42, 211-224. Ohba, T. (2002), Geothermal system of KusatsuShirane volcano, Report on Volcanic Structure in the Shallow Part and Volcanic Fluid, 161－168 (in Japanese). Ohba, T., J. Hirabayashi, and K. Nogami (2000), D/H and 18O/16O ratios of water in the crater lake at Kusatsu-Shirane volcano, Japan, J. Volcanol. Geotherm. Res., 97, 329-346. Ohba, T., J. Hirabayashi, and K. Nogami (1994), Water, heat and chloride budgets of the crater lake, Yugama, at Kusatsu-Shirane volcano, Geochem. J., 28, 217-231. Ohwada M, T. Ohba, J. Hirabayashi, K. Nogami, K. Nakamura, K. Nagao (2003), Interaction between magmatic fluid and meteoric water, inferred from 18O/16O and 36Ar/H2O ratios

of fumarolic gases at the Kusatsu-Shirane volcano, Japan, Earth Planets Space, 55, 105-110. Oskooi, B., Pedersen, L.B. , Smirnov, M., Árnason, K., Eysteinsson, H., Manzella, A. and the DGP Working Group (2005), The deep geothermal structure of the Mid-Atlantic Ridge deduced from MT data in SW Iceland, Phys. Earth Planet. Inter., 150, 183-195. Ossaka, J., Hayashi, T., Ando, Y., Kikawada, Y., Nogami, K., Hirabayashi, J., and Ossaka, T. (2005), Geochemical and geological study on the eruption of the Kusatsu-Shirane volcano in 1976 fingerprinted on the wall of the explosion crater, Bull. Volcanon. Soc. Japan,(submitted), (in Japanese with English Abstract). Pellerin, L., J.M., Johnston, and G.W., Hohmann, A numerical evaluation of electromagnetic methods in geothermal exploration. Geophysics, 61, 121-130, 1996. Sasaki, Y. (2001), Full 3D inversion of electromagnetic data on PC. J. Appl. Geophys. 46, 45 – 54. Shi, X., H. Utada, J. Wang, W. Siripunvaraporn (2005), Three-dimensional magnetotelluric forward modeling using vector finite method combined with divergence correction based on the magnetic fields (VFEH++), Siripunvaraporn, W., G. Egbert (2000), An efficient data-subspace inversion method for 2-D magnetotelluric data, Geophyscs, 65,3, 791-803. Tank, S.B., Y. Honkura, Y. Ogawa, N. Oshiman, M.K. Tuncer, M. Matsushima, C. Celik, E. Tolak, and A.M. Isikara (2003), Resistivity structure in the western part of the fault rupture zone associated with the 1999 Izmit earthquake and its seismogenic implication, Earth Planets Space, 55, 437-442. Unsworth, M.J., G.D. Egbert and J.R. Booker (1999), High resolution electromagnetic imaging of the San Andreas Fault in Central California, J. Geophys. Res., 104, 11311150. Uto, K. Hayakawa., Y., Aramaki, S., Ossaka, J. (1983), Geological map of Kusatsu-Shirane volcano, Geological Survey of Japan. (in Japanese) Yamazaki, A., Churei,M., Tsunomura, S., and Nakajima, S. (1992), Analysis of the variation of geomagnetic total force at Kusatsu-Shirane volcano: the remarkable changes in the geomagnetic total force in 1990 and the estimated thermal demagnetization model, Mem. Kakioka Mag. Obs., 24, 2, 53-66(in Japanese with English abstract).

35

MAKALAH 2 : SUBMIT Journal) , 2010

TO Earth and Planetary Sciences Journal (Int.

INVERSTIGATIO OF SUMATRAN FAULT DERIVED FROM MAGNETOTELLURIC MODELLING Nurhasan1, Y Ogawa2, F. Kimata3, D. Sutarno1, D Sugiyanto4 1 Physics Department, Bandung Institute of Technology, Bandung, Indonesia 2 Volcanic Fluid Research Center, Tokyo Institute of Technology, Tokyo, Japan 3 RESEARCH CENTER FOR SEISMOLOGY AND VOLCANOLOGY Nagoya University, Japan 4 Physics Department, Syiah Kuala University, Indonesia

Abstracts Two lines coast to coast broadband MT measurements were carried out in Aceh, Sumatra Island, Indonesia crossing the Sumatra fault. Using five components of electric and magnetic sensors, the time series data was recorded in the night time with 12 hours interval in average at 12 sites. Dimensionality analyses were done by using phase tensor and induction vector to see the 3D structure of the Sumatra Island. Interpretation of the 3D resistivity structure was made using 3D MT inversion provided by Weerachai’s code as well as 2D MT inversion. Based on these results, Sumatra fault is clearly detected by characterized by contrast resistivity just beneath the fault. 1.

Introduction

Sumatra Fault Zone which is located in Sumatra Island, Indonesia is an active fault as a result of strike-slip component of Indo-Australian oblique convergence. With the length of 1900 Km, Sumatra fault was divided into 20 segments starting from the southernmost which has small slip rate and increasing to the north end of Sumatra Island. A giant earthquake of Mw=9 stroked the Sumatra Island following by large tsunami which had wave magnitude up to 4 -5 m and amplitude of 2 m. The hypocenter of this event was detected in the south of Sumatra located at subduction interplate. Seismically, this megathrust event generated aftershock distributed not only along the trench of subduction interface but also along Sumatra Fault Zone especially in the northern part of Sumatra Fault Zone. Several multidisciplinary studies have been involved to investigate implication the giant earthquake to the region around the hypocenter and Sumatra Fault Zone. Through research collaboration among Nagoya University, Tokyo Institute of Technology, Bandung Institute of Technology and Syiah Kuala University, We were carried out Magnetotelluric

survey at 12 sites crossing the Sumatra fault and Seulimeum fault using MTU-5 system provided by Titech-Japan. The main goal of this research is to delineate structure of Sumatra and Seulimeum faults in form of resistivity distribution and their correlation to the earthquake generation and deformation process. 2.

Geological Setting

36 3.

Figure 2. Example of observed data which is representation data from west of the Sumatran Fault (a) and east of Sumatran Fault (b).

MT Measurements and Processing

MT broad band coast to coast measurements were conducted in two lines with the 27 total sites. The first line was done in the late of October and November 2008 crossing the Sumatra fault and Seulimeum fault through 65 Km of the length. We used the geophysical Phoenix Equipments (MTU-5A) provided by Titech-Japan through research collaboration to record two components of horizontal electric field, two components of the horizontal magnetic field and component of the vertical magnetic field. The time series data was recorded in the night time with 12 hours interval in average. Data processing and editing were done using SSMT 2000 embedded in Phoenix software. The sample of magnetotelluric data represented in apparent resistivity and phase are shown in figure 2. It is clear to see the significant difference between data obtained from the west part of Sumatra fault and data from east part of Sumatra fault. Data from the west of Sumatra fault are characterized relatively by high apparent resistivity while data from the east indicated by low apparent resistivity. This discrepancy is also shown in representation of induction vector and phase tensor as shown in figure 3.

4.

Data Representation

Figure 2 shows some representative MT data in frequency range between 320 Hz to 0.1 Hz. Relative big error bar are occurred in low frequency for all data. Limitation of the time length of recording data may be one of cause of this poor data. In general, the data can be divided by 2 types based on the region where data recorded. The data recorded at the west part of Sumatra fault characterized by the high resistivity, while in the east part is characterized by low resistivity. This indicates that in shallow part, resistivity structure should be high resistive in west and low resistive in the east. We have also analyzed the data plotted in term of induction vector and phase tensor to see lateral resistivity distribution as shown in figure 3. The variation of resistivity laterally distribution is clearly detected by induction vector and phase tensor. At the frequency of 320 Hz shape of ellipse phase tensors are distributed randomly indicating that shallow structure to be 3D structure. For lower frequencies corresponding to deeper structure, it is clearly the existence of the 2D structure representing form the direction of induction vector and shape of phase tensor.

A-12 B-16

Banda Aceh

A-1

Su m at ra

Fa ult

Meulaboh B-1

Figure 3. Observed Phase Tensor and Induction vector of the Line A in different frequencies Figure 1. MT sites plotted in the topographic map including Sumatra and Seulimeum Faults 5.

2D Modeling

As a usual procedure in MT 2D modeling, it is importance to determine strike direction before inversion. In this paper, strike direction was determined based on direction of the fault system that is clearly detected by induction vector and phase tensor diagram. Strike direction for the profile 1 is determined in 45 degree from the north

37 to east as shown in figure 4. This direction of the fault was also confirmed by geological studies . Figure 5 shows the final 2D inversion result using Ogawa and Uchida’s code calculated from apparent resistivity and phase for TM mode only. The use of TM mode only calculation is based on the region of the site location which is distributed in the north end of Sumatra fault surrounding by ocean. In this case, TM mode is the reliable mode because of the insensitivity to the boundary between sea and land . Homogeneous model of 100 ohm with the 0.3 Ωm. sea water resistivity included as fix parameter was used as initial model of inversion. Figure 5 (b) and (c) indicates the pseudosection of apparent resistivity and phase obtained form the final model. RMS was reach in 0.89 With the 20 iteration.

interpreted. In this test, we tested the big conductor (C1) by replacing it to high resistor (1000 ohm.m) in some different depth. The result shown that change of resistivity in this conductor C1 affect strongly the responses. It means that this conductor C1 is important feature. 6.

3D Inversion

The region of the study is located at the north end of Sumatra Island which is fully three dimensional structure. To overcome the effect of 2D structure caused by the ocean, 3D inversion using Weerachai’s code was performed to analyze the resistivity structure. The 3D model is designed into 100 x 100 x 50 Km in x ,y and z direction with the 100 ohm homogenous model as initial model. This model area was divided into 20 x 20 x 30 bolck using same grid in z and y direction. Vertical grids were constructed logarithmically with 50 m as the first grid at the surface. In this inversion, the ocean was modeled as fix parameter with the value of 0.3 ohm.m. The smallest rms was reached at the value of 3 in 10 iterations.

7. Interpretation and discussion Figure 4. Rose diagram in 4 decade frequencies obtained using Groom Bailey Decomposition technique

Sensitivity Test Sensitivity test was done to detect whether the importance features is real from structure or just artifact structure. This is very important to make sure that final model is strongly related to the data. If the result (feature) is not correspond to the data, it means that the feature is fake (not important) to be

Sumatra Fault is one of the srike-slip fault type where located at the subduction zone. Differ from many faults in the word like San Adreass Fault which is located in one segment along the land, Sumatra fault is segmented into 20 segments (Natawidjaja, 2000). Study of geoelectrical resistivity at fault zone has been discussion in many papers. Focus of study in the fault zone is not only how to interpret the resistivity distribution in the region of fault zone but also it can explain the mechanism of fault zone process. Spatial resistivity distribution and presence of the fluid is an important role in interpretation of the fault structure. San Andreas Fault which is a sample of srike-slip fault has several segments in different mechanism (Usswoth..). Most of the discussions about the srike-slip fault have shown that the low resistivity interpreted as fluid zone has strongly correlated to the seismicity distribution. Figure 5 shows the final model from 2D inversion which is look like to be an interesting structure correlated to the structure in fault zone. Based on the final model, we divided the resistivity distribution into shallow and deep structures for interpretation. The shallow part with depth up to 3 km, resistivity structure can be seen as three vertical blocks where high resistivity in the west and east of the profile and low resistivity in the middle of the profile. Geologically, western part of

38 the Sumatra Fault is a lower cretaceous – upper Jurasic rocks which electrically has high resistivity (R1). While Low resistivity in the west of fault indicated the existence of volcanic rock or volcanic sediment, Holocene- Pleistocene which was confirmed exactly by geological studies . There is an evident that in the east of MT profiling an active volcano. The sharp boundary between C1 and R1 is interpreted as strike-slip Sumatran Fault which is a site location in this area is a boundary fault zone. This sharp boundary is a typical structure that can occurred in the srike-slip fault which the dip-slip angle around 90 degree. This model of srike-slip fault characterized by sharp boundary has been performed by 2D modeling ( Unswooth et al., 2003). The sharp boundary of resistivity block which is characteristic of strike-slip fault is also detected in line B. Slightly differ from line A, shallow structure from line B is more complex. This complexity was detected well by geological structure. West of the profile is covered by Holocene-Pleistocene rock. Middle of the profile is lower Cretaceous-Upper Jurasic rocks which is higher resistivity nad the east of the profile is characterized by volcanic rocks and Pliocene-Eocene rocks. Interpretation of deep structure is not easy from the MT study only. Based on the final models, it can be seen that line A and line B have the similar resistivity structure which is a vertical conductors exist in the middle of the profile. Many paper explained that such conductor located at the depth below 20 Km form the surface was interpreted as melting zone (Tank et al., 2003). Since Sumatra Fault is laid above the intersection subduction plate, this malting fluid can be one of the candidates for these vertical conductors. The existence of conductor C 2 in line A is interpreted as lower crust shear zone

8.

Conclusion

We have successfully imaged the structure of Sumatra and Seulimeum faults from MT data. Resistivity structure shows that the fault zone is characterized by contrast resistivity. By comparing with the GPS data, it is shown that conductive part located beneath the fault is correlated to the depth of locked zone in GPS studies.

9.

References

Natawidjaja, D ,Wahyu Triyoso, The Sumatran Fault Zone – From Source to Hazard , Journal of Earthquake and Tsunami, Vol. 1, No. 1 (2007) 21–47

(LCSZ) that can be exist at the strike-slip fault zone (Unsworth et al., 2003). Unswooth has modeled the kind of structures to test the effect of shear zone and fault zone. This shear zone is a part that can be easy to move because located just beneath the fault zone and also in the boundary ductile-brittle region. GPS measurements which are same project with this MT measurement were carried out in this part. Large displacement obtained from GPS data indicating that the 2004 giant earthquake caused the post-seismic of slip distribution in this region is still occurred. In addition to the slip distribution, GPS result was also detected the locking deep which is assumed as a source of earthquake. By analyzing slip rate of the Sumatra fault for 3 segments (Aceh, Seulimeum and Tripa segments), it has been founded that the locking deep is located at the depth of 10 Km from the surface along the fault. Comparing to the resistvity distribution as described above. It is believed that the locking zone is consitensly to the shear zone which is characterized by low resistivity. Interpratation of deeper part of the resisitivity structure from the final model is based on resistive blocks namely C means conductor and R means Resistor. Conductor C2 in the line 1 model as interpreted as the lower-crust share zone (LCSZ) which is a fracture zone located in the lower crust. This conductor C1 is also appeared in the eastern part as implication of another fault which much small fault that Sumatra fault. Hence the resistivity of the lower crust shear zone beneath this fault is much less that the west part.

Ague et al., 1998 J.J. Ague, J. Park and D.M. Rye, Regional metamorphic dehydration and seismic hazard, Geophys. Res. Lett. 25 (1998), pp. 4221–4224. . Çağlar, 2001 I. Çağlar, Electrical resistivity structure of the northwestern Anatolia and its tectonic implications for the Sakarya and Bornova zones, Phys. Earth Planet. Int. 125 (2001), pp. 95–110. Gamble et al., 1979 T.D. Gamble, W.M. Goubau and J. Clarke, Magnetotellurics with remote magnetic reference, Geophysics 44 (1979), pp. 53–68. Groom and Bailey, 1989 R.W. Groom and R.C. Bailey, Decomposition of magnetotelluric impedance tensors in the presence of local three dimensional galvanic distortions, J. Geophys. Res. 94 (1989), pp. 1913–1925.

39 Honkura et al., 2000 Y. Honkura, A.M. Işıkara, N. Oshiman, A. Ito, B. Üçer, S. Barış, M.K. Tunçer, M. Matsushima, R. Pektaş, C. Çelik, S.B. Tank, F. Takahashi, M. Nakanishi, R. Yoshimura, Y. Ikeda and T. Komut, Preliminary results of multidisciplinary observations before, during and after the Kocaeli (İzmit) earthquake in the western part of the North Anatolian fault zone, Earth Planets Space 52 (2000), pp. 293–298. Honkura et al., 2002 Y. Honkura, M. Matsushima, N. Oshiman, M.K. Tuncer, S. Barış, A. Ito, Y. Iio and A.M. Isikara, Small electric and magnetic signals observed before the arrival of seismic wave, Earth Planets Space 54 (2002), pp. e9–e12. Ito et al., 2002 A. Ito, B. Üçer, S. Barış, A. Nakamura, Y. Honkura, T. Kono, S. Hori, A. Hasegawa, R. Pektaş, T. Komut and A.M. Işıkara, Aftershock activity of 1999 İzmit earthquake, Turkey, revealed from microearthquake observations, Bull. Seismol. Soc. Am. 92 (2002), pp. 418–427. Matsushima et al., 2002 M. Matsushima, Y. Honkura, N. Oshiman, S. Barış, M.K. Tuncer, S.B. Tank, C. Çelik, F. Takahashi, M. Nakanishi, R. Yoshimura, R. Pektaş, T. Komut, E. Tolak, A. Ito, Y. Iio and A.M. Işıkara, Seismoelectronic effect associated with the İzmit earthquake and its aftershocks, Bull. Seismol. Soc. Am. 92 (2002), pp. 350– 360. Nakamura et al., 2002 A. Nakamura, A. Hasegawa, A. Ito, B. Üçer, Ş. Barış, Y. Honkura, T. Kono, S. Hori, R. Pektaş, T. Komut, C. Çelik and A.M. Işıkara, P-wave velocity structure of the crust and its relationship to the occurence of the 1999 İzmit, Turkey, earthquake and aftershocks, Bull. Seis. Soc. Am. 92 (2002), pp. 330–338. Ogawa et al., 2001 Y. Ogawa, M. Mishina, T. Goto, H. Satoh, N. Oshiman, T. Kasaya, Y. Takahashi, T. Nishitani, S. Sakanaka, M. Uyeshima, Y. Takahashi, Y. Honkura and M. Matsushima, Magnetotelluric imaging of fluids, in intraplate earthquake zones, NE Japan back arc, Geophys. Res. Lett. 28 (2001), pp. 3741–3744. Ogawa et al., 2002 Y. Ogawa, S. Takakura and Y. Honkura, Resistivity structure across Itoigawa-Shizuoka tectonic line and its implications for concentrated deformation, Earth Planets Space 54 (2002), pp. 1115– 1120. Ogawa and Uchida, 1996 Y. Ogawa and T. Uchida, A two-dimensional magnetotelluric inversion assuming Gaussian static shift, Geophys. J. Int. 126 (1996), pp. 69–76.

Tank et al., 2003 S.B. Tank, Y. Honkura, Y. Ogawa, N. Oshiman, M.K. Tunçer, M. Matsushima, C. Çelik, E. Tolak and A.M. Işıkara, Resistivity structure in the western part of the fault rupture zone associated with the 1999 İzmit earthquake and its seismogenic implication, Earth Planets Space 55 (2003), pp. 437–442. Unsworth et al., 1997 M.J. Unsworth, P.E. Malin, G.D. Egbert and J.R. Booker, Internal structure of the San Andreas fault at Parkfield, California, Geology 25 (1997) (4), pp. 359–362. Unsworth et al., 2000 M.J. Unsworth, P.A. Bedrosian, M. Eisel, G.D. Egbert and W. Siripunvaraporn, Along strike variations in the electrical structure of the San Andreas Fault at Parkfield, California, Geophys. Res. Lett. 27 (2000), pp. 3021–3024. Irwan, M, et all, GPS measurement of coseismic displacement in Aceh province after the 2004 Aceh-Andaman earthquake, Report, 2005 Natawidjaja, J. Galetzka, B. Suwargadi, Y.-J. Hsu, M. Simons, N. Hananto, I. Suprihanto, D. Prayudi, J.-P. Avouac, L. Prawirodirdjo and Y. Bock (2006). Deformation and slip along the Sunda megathrust during the giant NiasSimeulue earthquake of March 2005, Science, Natawidjaja, D. H., K. Sieh, S. Ward, H. Cheng, R. L. Edwards, J. Galetzka, and B. W. Suwargadi, 2004. Paleogeodetic records of seismic and aseismic subduction from central Sumatran microatolls, Indonesia, Journal of Geophysical Research, 109(B4): 4306, 1–34. Natawidjaja, D et al. (2006). The giant Sumatran megathrust ruptures of 1797 and 1833: Paleoseismic evidence from coral microatolls, Journal of Geophysical Research. Natawidjaja, D. H. (1997). Tectonics of the Sunda Strait. Unpublished research for Ph.D proposition, Caltech. Natawidjaja, D. H. and K. Sieh (1994). Slip rates along the Sumatran transcurrent fault and it’s tectonics significance. Abstract in Proceeding on Tectonic Evolution of Southeas Asia, Geol. Soc. of London, 7–8 December, p. 38. Natawidjaja, D., Y. Kumoro and J. Suprijanto (1995). Gempa bumi tektonik di daerah Bukit tinggi — Muaralabuh: Hubungan segmentasi sesar aktif dengan gempa bumi tahun 1926 dan 1943. Proceeding of Annual Convention of Geoteknologi-LIPI, Bandung, Indonesia.

1 MAKALAH 3 : SUBMIT TO Indonesian Physics Journal (Nasional Journal) , 2010

Dimensionality Analysis of Resistivity Structure of Volcanic Zone from Magnetotelluric Data Nurhasan1 , D. Sutarno1, Y. Ogawa2,3 1 Physics Department, Bandung Institute of Technology, Bandung, Indonesia 2 Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo, Japan 3 Volcanic Fluid Research Center, Tokyo Institute of Technology, Tokyo, Japan

Abstract

In many cases, three-dimensional resistivity structures are often approximated by twodimensional models without checking the dimensionality of the structure prior to perform modeling. However, such approximation can be misleading if the structure is purely 3-D where electromagnetic fields can not be separated into TE and TM modes. Then, a dimensionality analysis is important in order to get the general feature of the structure in particular in 3-D structure as expected in volcanic area. There are many methods to analyze dimensionality such as Groom-Bailey decompositions, which assume that the regional structure is two-dimensional, and Bahr’s method. Here, we examine the dimensionality mainly by the phase tensor, which does not assume regional two-dimensional structure at all. The parameter “beta” is also used as an index for the three-dimensionality of the structure. On the other hand, the parameter “alpha” is the directional parameter. We also map the phase tensor diagrams (tan-1(22) as a function of the coordinate angle) and the induction vectors. In this paper, we have also examined the effect of regional three-dimensional structure to the 2D model. The synthetic and real Magnetotelluric data obtained from volcanic zone were used in this study. 1. Introduction Three-dimensional resistivity structures are often approximated by two-dimensional models. However, such approximation can be misleading if the structure is purely 3-D where electromagnetic fields can not be separated into TE and TM modes. However, a dimensionality analysis is important in order to get the general feature of the structure in particular in 3-D structure. Dimensionality analyses were applied using distortion parameters (e.g. skew, phase sensitive skew, phase different) for checking dimensionality of the data (Ledo et. al., 1998 ; 2002). The limitation of these methods is that these parameters are still affected by the existence of near surface heterogeneity although these are rotationally invariant. In Groom-Bailey decompositions (Groom et. al., 1989), which assume that the regional structure is two-dimensional. In this paper, we examined dimensionality of the data using phase tensor and induction vector analyses. Unlike the conventional polar diagram, the phase tensor is not affected by three-dimensional shallow structure or galvanic distortion (Caldwell et al., 2004; Bibby et al., 2005). Parameter “alpha” and “beta” as part of the phase tensor are used in this study for checking dimensionality. The induction vector is applied to check the lateral variation.

1

2

2. Methods 2.1. Phase tensor In this method, we adopted the phase tensor method proposed by Caldwell et al (2004), which is not affected by galvanic distortion for three-dimensional regional structures. The observed (distorted) complex impedance tensor can be separated into a real part (X) and an imaginer part (Y) as follows. Z  X  iY Similarly, the regional (undistorted) complex impedance tensor can be separated into a real part (XR) and an imaginer part (YR) as follows. Z R  X R  iY R The magnetotelluric phase tensor is defined as the ratio between the real part and the imaginer part of the impedance tensor. For observed (distorted) impedance, the phase tensor can be expressed as   X 1Y (1) In term of the real and imaginer components of impedance tensor, the phase tensor can be expressed as

  11   21

12  1  X 22Y11  X 12Y21    22  det X   X 11Y21  X 21Y11

X 22Y12  X 12Y22  X 11Y22  X 21Y12 

where det  X   X 11 X 22  X 11 X 12 In the plotting of the phase tensor, we calculated the arctangent of the YY-component of the phase tensor as a function of the coordinate angles (X direction of the rotated frame) by with 3 degree steps. This plotting is different from those originally defined by Caldwell et al. (2004). Over a one-dimensional isotropic earth, the phase tensor appears a circle due to orientation independence of electric and magnetic fields. In a simple of 2-D case where the model consists of two vertically different resistivity regions (vertical contact model), the phase tensor will have the appearance of either circle or ellipse oriented in the direction of E field, depending on the distance from the boundary. The site located on the resistive side near boundary, phase tensor will be elliptic where the major axis is oriented parallel to the structure. On the other hand, the site located on the conductive side, major axis of the ellipse is perpendicular to the contact.

By using the singular value decomposition approach, the phase tensor can be separate to some matrices as follow:    R T     max  0

0  R      min 

(2)

2

3 where     21      21  1 1  ;   tan 1  12    tan 1  12 2 2   11   22   11   22 

 min   12   32    12   32   22  12



 max   12   32



12

12



  12   32   22



12

The andrepresent the strike direction and three-dimensionality, respectively. 2.2 Induction vector Besides impedance transfer function, another transfer function called “magnetic transfer function (Induction vector)” is important for describing lateral variation of resistivity. Since the magnetic field is free from galvanic distortions, the induction vectors are also free from distortions. Mathematically, the induction vector (T) is expressed as a ratio of vertical (z) to horizontal magnetic (Hx and Hy) fields. H z  Tzx H x  Tzy H y

(3)

The induction vector as defined as (-Tzx, -Tzy) using Parkinson’s convention, reflects the lateral resistivity anomaly. Graphically the induction vector is defined as the normal unit vector of the magnetic field by projecting it to the ground. The vector will point to the conductive side. 3. Application to MT data 3.1. Phase Tensor and Induction Vector We applied these methods to the real MT data obtained from volcanic region, i.e. Kusastu Shirane volcano, Japan and Papandayan volcano, Indonesia. Measured phase tensor plotted together with induction vector (solid line) for Kusatsu Shirane MT data are shown in Figure 1 for three different frequencies ( 100Hz, 10Hz and 1Hz), representative for shallow, intermediate (around 500 m) and deep ( > 1 km) penetration depths, respectively. (a) f=100 Hz

(b) f=10 Hz Longitude

138.5300

138.5350

Longitude 0

138.540

0

138.5250

138.545

36.6500

36.6500

36.6460

36.6460

Latitude

Latitude

138.5250

36.6420

138.5350

138.5400

138.5450

36.6420

0.2

0.2

900 36.6380

138.5300

0

0

90

200

400

0

36.638

600

Meter

0

200

400

600

Meter

(c) f=1 Hz 3

4 Longitude 138.525 0

138.530 0

138.5350

138.5400

138.5450

0

Latitude

36.650

36.6460

36.6420

0.2 900 36.6380

0

200

400

600

Meter

Figure 1. Measured phase tensor (blue color) and induction vector (red line). Small blue cross denote distribution of seismicity.

3.2 Parameter beta Figure 2 shows the “beta” distribution at the summit area in five different frequencies, i.e., 10 kHz, 1 kHz, and 10 Hz. Dot symbols represent AMT sites (red color) and MT sites (blue color). At high frequencies (10 kHz, 1000 Hz and 100 Hz), contour area is limited, as compared with low frequencies (10Hz and 1Hz), because the sites at the north western corner have no data over 320Hz.. (a) f = 10 kHz

(b) f = 1 kHz

(c) f = 10 Hz

4

5

Figure 2. Distribution of parameter beta for 5 different frequencies 3.3 Parameter alpha We can check the directional properties of the structure using “alpha”, which is similar to the strike direction in two dimensional structures. (a) f = 10 kHz (b) f = 1 kHz

( c ) f = 10 Hz

( e ) f = 1 Hz

Figure 3. Distribution of parameter alpha in 5 different frequencies 4. Discussion

5

6 By analyzing direction of the major and minor axes of the ellipses, we can predict the boundary of the resistivity anomaly. The circle-shaped phase tensors as shown at sites located in the middle of the volcano (Figure 1), indicate that the sites are located in the center of anomaly far away enough from the boundary. On the other hand, the elliptic phase tensors as shown at site located eastern part of the volcano, mean the eastern and western boundary of the conductive anomaly. Based on this explanation, we can depict the elliptic conductivity anomaly beneath the Mizugama crater (shown by blue dash line in Figure 1.b). In the inductive vector analysis, at high frequency (100 Hz), directions of inductive vectors strongly vary with locations, because of the effect of topography or effect of nearly conductivity anomaly such as vents or hydrothermal manifestations. At the frequency 10 Hz, the real induction vectors point consistently to the Mizugama crater with magnitude range of 0.02 to 0.20. Although some induction vectors are not consistent, it can be suggested that the conductive anomaly is located beneath the Mizugama crater. To confirm the ability of the phase tensor and induction vector in checking dimensionality, we also examined 3D MT inversion using Siripunvaraporn’s code (Siripunvaraporn et al., 2005). Based on this result, we have found that resistivity structure of Kusatsu Shirane volcano can be divided by two parts. The three-dimensional structure has been found at the shallow part and the 2-D structure has been found in the deeper part. The phase tensor and induction vector analyses as explained before are consistently to the 3D inversion results. Based on the parameter alpha and beta, in general, we can classify the whole area into two, depending on the value of beta; one with large beta corresponding to 3-D structure and the other with small beta corresponding to 1-D or 2-D structure. In Figure 2, large beta values (   2 0 ) are distributed dominantly at high frequencies (10 kHz and 1000 Hz). It means that in shallow depth (- 500 m from the surface) is characterized by 3-d structure. On the other hand, deep structures corresponding to the low frequencies (10 Hz) are dominated by small beta (   2 0 ). This means that the three-dimensionality of the deep structure is weak and the deep structures are approximately two dimensional. According to Figure 3, it is clear that 3-D structure is seen at high frequencies (10kHz and 1000Hz ) that are characterized by the inconsistency of the distribution of alpha. Parameter alpha itself cannot be used to represent three-dimensionality. However, the distribution of alpha for many sites or frequencies can give us information of dimensionality by checking their spatial and frequency consistency. At low frequencies (10Hz and 1Hz), alpha shows consistency around 0 degree that is an indication of 2-D structure with orientation of strike in the north-south direction. 5. Conclusion In conclusion, we have successfully analyzed dimensionality using free distortion parameters (phase tensor and induction vector) applied to MT data of volcanic zone, Kusatu Shirane volcano. The three-dimensional resistivity structure consisting of conductive zone surrounded by resistive part is clearly detected by phase tensor and induction vector. Moreover, the existence of three-dimensional structure at shallow part and 2-D structure at deep part are also confirmed from parameters alpha and beta analyses. A amazing result has found that there is a good agreement between 3-D MT inversion result and analyses of these free distortion parameters.

6. References

6

7 Bahr, K., Geological noise in magnetotelluric data : a classification of distortion types. Phys. Earth Planet. Inter., 66, 24-38, 1991. Bibby, H.M., T.G. Caldwell, and C. Brown, Determinable and non-determinable parameters of galvanic distortion in magnetorllurics, Geophys. J. Int., 163, 915 – 930, 2005 Cagniard, L., Basic theory of the magnetotelluric method of geophysical prospecting. Geophysics, 18, p.605, 1953 Caldwell, T.G., H.M. Bibby, and C. Brown, The magnetotelluric phase tensor, Geophys. J. Int., 158, 457 – 469, 2004 Groom, R. W. and R.C. Bailey, Decomposition of magnetotelluric impedance tensor in the presence of local three-dimensional galvanic distortion, J. Geophys. Res., 94, 1913– 1925, 1989. Ledo, J., P. Queralt, and J. Pous, Effect of galvanic distortion on magnetotelluric data over three-dimensional regional structure, Geophys, J. Int., 132, 295 - 301, 1998. Ledo, J., P. Queralt, A. Marti, A.G. Jones, Two-dimensional interpretation of threedimensional magnetotelluric data: an example of limitation and resolution, Geophys, J. Int., 150, 127-139, 2002. Mackie, R.L., Madden, T.R. and Wannamaker, P.E., Three-dimensional magnetotelluric modeling using finite difference equations – Theory and comparisons to integral equation solutions: Geophysics, 58, 215-226, 1993. Muller A, and V. Haak, 3-D modeling of the deep electrical conductivity of Merapi volcano (Central Java): integrating magnetotellurics, induction vectors and the effects of steep topography, J. Volcano. Geotherm. Res., 138 (3-4): 205-222, 2004. 9.1.1.1. Nurhasan , Y. Ogawa , N. Ujihara, S.B. Tank , Y. Honkura, S. Onizawa,, T. Mori , and M. Makino, Two electrical conductors beneath Kusatsu-Shirane volcano, Japan, imaged by audiomagnetotellurics and their implications for hydrothermal system, Earth Planets Space, 2006 (in press). Ogawa, Y., On two-dimensional modeling of magnetotelluric field data, Surv. Geophys., 23 (2-3), 251-273, 2002. Ogawa, Y., N. Matsushima, H. Oshima, S. Takakura, M. Utsugi, K. Hirano, M. Igarashi, and T. Doi, A resistivity cross-section of Usu volcano, Hokkaido, Japan, by audiomagnetotellurics soundings, Earth Planets Space, 50, 339-346, 1998. Shi, X., H. Utada, J. Wang, W. Siripunvaraporn, Three-dimensional magnetotelluric forward modeling using vector finite method combined with divergence correction based on the magnetic fields (VFEH++), Siripunvaraporn W, Egbert G, Lenbury Y, Uyeshima M. Three-dimensional magnetotelluric inversion: data-space method. Phys Earth Planet In May 2005;150(1-3):3-14.

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