Mengenang Tsunami Jepang 2011

Hari itu mendapatkan email dari salah satu penasihat komunikasi GNS untuk menulis di media. Sebentar lagi peringatan 10 tahun tsunami Jepang yang menyebabkan kerugian material dan korban jiwa yang terbesar dalam sejarah Jepang. Science Magazine akan mengeluarkan review tentang kejadian tersebut yang ditulis oleh peneliti dari Jepang. New Zealand memiliki Science Media Centre yang secara rutin menerbitkan tanggapan oleh para ahli tentang suatu temuan atau kebijakan penting.

Baru saja terjadi tiga tsunami di New Zealand. Dan saya sedang tidak kekurangan pekerjaan. Rasanya ingin sekali menolak menulis karena hanya akan menambah pekerjaan. Tetapi secara moral seharusnya saya melakukan sesuatu untuk mengenang tsunami tersebut. Lagi pula sepertinya di GNS tidak ada orang yang lebih tepat lagi mereview kejadian tsunami di Jepang selain saya.

Paper Science tersebut akhirnya saya baca. Baru membaca paragraf ternyata banyak hal yang dahulu pernah saya pelajari kembali lagi. Waktu di Jepang tidak sedikit melihat presentasi tentang riset tsunami Tohoku 2011. Setelah membaca sekali, sepertinya sudah siap untuk membuat draft review. Rerview saya tulis perlahan dengan beberapa kali membaca ulang apa yang ada di Paper. Dikepala ini seperti memainkan informasi yang dulu pernah diterima dengan informasi dari paper.

Akhirnya orderan si penasihat tadi untuk menghasilkan tulisan dalam beberapa jam saja saya penuhi. Ngordernya sore, harus jadi besok paginya. Serasa mahasiswa lagi. Besoknya si John datang kekantor untuk lebih lanjut ngobrol-ngobrol tentang pengalaman saya ketika kejadian. Pada saat gempa saya sedang menghadiri seminar tentang tsunami Aceh 2004 di Kampus Kashiwa Tokyo Daigaku. Dan ternyata bukti fotonya ada.

May be an image of 23 people, including Udrekh Hanif and Rahma Hanifa and people standing
Foto bersama peserta seminar setelah merasakan guncangan dari gempa Tohoku 2011 di kampus Universitas Tokyo di Kashiwa. Foto ini di dapat dari halaman facebooknya Rahma Hanifa (peneliti Indonesia berjilbab yang ada di foto).

Judul paper yang Science yang dimaksud berjudul

Investigating a tsunamigenic megathrust earthquake in the Japan Trench

Komentar yang saya berikan untuk paper tentang tsunami Tohoku yang dipublikasi di sini adalah sebagai berikut:

Dr Aditya Gusman, Tsunami Modeller, GNS Science, comments:

“At the time of this event I was at a conference on the 2004 Indian Ocean earthquake and tsunami at The University of Tokyo, some 500km from the quake epicentre. Once the strongest shaking stopped – during which it was difficult to stand up – we evacuated the building. Highrise buildings everywhere were swaying markedly. Strong aftershocks continued for days. Trains stopped shortly after the earthquake and many people had to walk home. Some stayed at train stations because it was too far to walk. Supermarkets gave out emergency supplies such as blankets, water, and food for those unable to go home.

“This paper reviews the main findings from investigations following the 2011 Tōhoku earthquake. The event produced huge datasets that can be used to better understand the Japan subduction zone. The rich datasets are the result of Japan’s dense networks of seismic, geodetic and tsunami instruments.

“Large tsunamis were known to have occurred in the past from earthquakes in the Japan trench from historical records as well as geological evidence of tsunami deposits along Japan’s east coast. The 2011 Tōhoku tsunami runups reached a maximum of 40m, and were higher than 20m along 200km of Tōhoku coast.

“The large tsunami was estimated to have been caused by the large fault slip near the trench. Horizontal slip displacements of more than 30m were recorded at underwater geodetic stations.

“Scientific drilling into the rupture zone near the trench revealed that the plate boundary was confined by a layer of pelagic clay. The weakness of this clay layer may help to explain the very large slip. The probability of another M9 earthquake soon in this region is low.

“However, the stress state after the 2011 Tōhoku thrust earthquake might bring other types of tsunamigenic earthquakes closer to rupture. The earthquake has already been followed by one normal-faulting event that generated small tsunami.”

Supersite for the 2018 Palu Earthquake (Mw 7.5)

 

 

USGS event page:

https://earthquake.usgs.gov/earthquakes/eventpage/us1000h3p4/executive

Indonesian Tsunami Early Warning System (InaTEWS)

http://inatews.bmkg.go.id/light/?

The list of warning messages from InaTEWS

http://inatews.bmkg.go.id/new/tsunami15.php

First warning http://inatews.bmkg.go.id/new/view_event.php?eventid=20180928170738&tab=7

Second warning (cancellation) http://inatews.bmkg.go.id/new/view_event.php?eventid=20180928173612&tab=7

Google crisis maps of before and after the earthquake and tsunami:

https://goo.gl/u8YaGg

Satellite images before and after the earthquake and tsunami from Digital Globe:

http://go.digitalglobe.com/m000uz3070EhiUfOENR0PE0

Geospatial vector data (shapefiles) for GIS from the Indonesia Geospatial Agency:

https://cloud.big.go.id/index.php/s/sxb9TEStoDYT276

Reuters page

https://fingfx.thomsonreuters.com/gfx/rngs/INDONESIA-QUAKE/010080KV15C/index.html

Peta lokasi pengungsian, jumlah pengungsi, dan kebutuhan yang diperlukan https://www.google.com/maps/d/u/0/viewer?mid=1rWj-k3enEZl5cRLXDnG_T7MBjHs15lua&ll=-0.9019903921434881%2C119.87124221732904&z=14

 

Tsunami videos

 

 

Tsunami video from afar

Tsunami Data Assimilation with MOANA Network

Mungkin ini salah satu kerjaan yang gak beres-beres. Waktu yang dialokasikan untuk pekerjaan ini tidak pernah terlalu lama. Sehigga perkejaannya tidak bisa langsung selesai. Selain itu karena  saya bukan penulis pertamanya. Jadi tidak mau terlalu proaktif.

Pada dasarnya pekerjaan berawal dengan penentuan source model dengan menggunakan data tsunami. Selain data tsunami ada juga data GPS yang bisa digunakan. Tetapi untuk menggunakan kedua data secara bersamaan, parametrerisasi inversi menjadi lebih banyak. Karena data GPS bisa memberikan informasi sudut rake, akan lebih baik jika sudut rake dijadikan sebagai variabel yang dicari dalam inversi. Tetapi desain awalnya sudut rake di fix-kan. Hasil yang diperoleh diperuntukkan untuk koreksi gelombang yang terekam oleh pressure gauges MOANA stations. Jadi setelah dapat tsunami fit yang cukup bagus, maka disudahkanlah pekerjaan source modeling. Dengan membuat rake sebagai variable sebenarnya waveform fitting bisa lebih bagus. Begitulah seharusnya.

Saat ini koreksi hanya menggunakan hasil dari tsunami waveform inversion. Setelah waveforms dikoreksi selanjutnya dilakukan eksperimen prediksi tsunami dengan metoda tsunami data assimilation. Hasilnya sudah lumayan. Meskipun sebenarnya waveform fit di tide gauge yang dijadikan sebagai target masih kurang sempurna. Plot yang diperlukan untuk keperluan publikasi seperti wave-field plots and animasi sudah dibuat. Plot yang menunjukkan imporvement jika menggunakan data yang lebih banyak atau time window yang lebih lama sudah dibuat. Sepertinya untuk saat ini segini dulu. Kalau mengikuti apa yang diinginkan bisa lebih lama lagi pekerjaan ini berjalan sebelum bisa publikasi.

 

Optimum sea surface displacement and fault slip distribution of the 2017 Tehuantepec earthquake (Mw 8.2) in Mexico estimated from tsunami waveforms

Key Points:

  1. Tsunami waveforms resolve the optimum sea surface displacement with maximum sea surface uplift of 0.5 m and subsidence of 0.8 m.
  2. Large fault slip (3 – 6 m) located at depths between 30 – 90 km is estimated from the optimum sea surface displacement.
  3. Large tsunami amplitudes up to 2.5 m due to edge waves are estimated inside and around a lagoon between Salina Cruz and Puerto Chiapas.

 

Abstract

The 2017 Tehuantepec earthquake (Mw 8.2) was the first great normal fault event ever instrumentally recorded to occur in the Middle America Trench. The earthquake generated a tsunami with an amplitude of 1.8 m (height=3.5 m) in Puerto Chiapas, Mexico. Tsunami waveforms recorded at coastal tide gauges and offshore buoy stations were used to estimate the optimum sea surface displacement without assuming any fault. Our optimum sea surface displacement model indicated that the maximum uplift of 0.5 m is located near the trench and the maximum subsidence of 0.8 m on the coastal side near the epicenter. We then estimated the fault slip distribution that can best explain the optimum sea surface displacement assuming ten different fault geometries.  The best model suggests that a compact region of large slip (3 – 6 m) extends from a depth of 30 km to 90 km, centered at a depth of 60 km.

Keywords: the 2017 Tehuantepec earthquake, tsunami waveform inversion, optimum sea surface displacement, fault slip distribution, tsunami simulation.

See manuscript here

The 2017 Mexico Tsunami – GRL

Terpilih sebagai salah satu AGU’s Outstanding Reviewer 2016

Pada akhir bulan Maret 2017 dihubungi oleh kantor editor AGU Journals. Karena terpilih sebagai salah satu Outstanding Reviewer (Pemeriksa Luar Biasa). Mereka dipilih karena banyak sekali memeriksa naskah ilmiah dan memberikan kualitas pemeriksaan yang bagus secara berulang ulang. Waktu itu saya agak menggerutu karena baru saja dapat undangan untuk memeriksa naskah ilmiah. Rasaya sudah banyak sekali naskah yang saya periksa. Seorang reviewer (pemeriksa) ini hampir tidak dikenali kontribusinya karena biasanya memberikan laporannya secara anonymous (tidak bernama). Memeriksa naskah ilmiah bukan perkara mudah karena kita juga harus membulak balik banyak referensi, setidaknya untuk memeriksa satu naskah saya harus baca lagi 5 atau 6 referensi penting. Kemudian harus bisa memberikan diantaranya, komentar membangun untuk naskah yang sedang di periksa dan memastikan tidak ada kesalahan fatal. Tapi di akhir hari saat saya hampir menolak tugas mereview itu, datang pemberitahuan “Outsanding Reviewer” ini.

Halaman tentang penghargaan ini dapat dilihat di sini: https://eos.org/agu-news/in-appreciation-of-agus-outstanding-reviewers-of-2016

Tsunami Simulation for the 22 January 2017 Earthquake occurred on​ Bougainville Island, Papua New Guinea

W-phase Moment Tensor Solution (USGS)

Event time: 2017-01-22 04:30:23 UTC.

Seismic Moment: 9.75e+20 Nm.

Magnitude: 7.9 Mw.

Focal depth: 136 km.

Epicenter: 6.214°S and 155.122°E.

Fault Model

Strike/dip/rake: 298°/37°/76° (Nodal Plane 1)

Fault dimension: 96 km × 48 km.

Slip amount: 5.2 m.

Tsunami Simulation Result

Based on tsunami simulation, the maximum tsunami amplitude along the coast of Bougainville Island is up to 1.2 m. The maximum tsunami amplitude around Buka Town is 0.8 m. The tsunami is confined by the Solomon Basin and only very small tsunami energy escape the Basin. While tsunami amplitudes along the coast of other islands around the Solomon Basin are less than 20 cm.

 

trimzmax3-ps

Simulated maximum tsunami amplitude from the 2017 Bougainville earthquake (Mw 7.9). Red rectangle indicates the earthquake fault model and red star indicates the epicenter.

 

Tsunami data assimilation of Cascadia seafloor pressure gauge records from the 2012 Haida Gwaii earthquake

Abstract

We use tsunami waveforms recorded on a dense array of seafloor pressure gauges offshore Oregon and California from the 2012 Haida Gwaii, Canada, earthquake to simulate the performance of two different real-time tsunami-forecasting methods. In the first method, the tsunami source is first estimated by inversion of recorded tsunami waveforms. In the second method, the array data are assimilated to reproduce tsunami wave fields. These estimates can be used for forecasting tsunami on the coast. The dense seafloor array provides critical data for both methods to produce timely (> 30 minutes lead time) and accurate in both timing and amplitude (> 94% confidence) tsunami forecasts. Real-time tsunami data on dense arrays and data assimilation can be tested as a possible new generation tsunami warning system.

http://onlinelibrary.wiley.com/doi/10.1002/2016GL068368/abstract?campaign=wolacceptedarticle

https://www.researchgate.net/publication/301344525_Tsunami_data_assimilation_of_Cascadia_seafloor_pressure_gauge_records_from_the_2012_Haida_Gwaii_earthquake

Lima puluh tahun Pasific Tsunami Early Warning System

Pasific Tsunami Early Warning System didirikan pada tahun 1965. Buku yang diterbitkan oleh International Tsunami Information Center (NOAA) ini menceritakan perjalanan organisasi ini dari mulai berdiri sampai 50 tahun kemudian. Terdapat juga ringkasan kejadian-kejadian tsunami besar yang mengakibatkan kerusakan parah.

Untuk lengkapnya silahkan lihat file pdf dengan 203 halaman yang dapat didownload dibawah ini:

Cover buku

Cover buku


Download pdf

Publications

Gusman, A. R., and Tanioka, Y., (2015), Effectiveness of Real-Time Near-Field Tsunami Inundation Forecasts for Tsunami Evacuation in Kushiro City, Hokkaido, Japan, Post-Tsunami Hazard, Advances in Natural and Technological Hazards Research Volume 44, pp. 157-177, doi: 10.1007/978-3-319-10202-3_11.

Heidarzadeh, M., K. Satake, S. Murotani, A. R. Gusman, and S. Watada, (2014), Deep-Water Characteristics of the Trans-Pacific Tsunami from the 1 April 2014 Mw 8.2 Iquique, Chile Earthquake, Pure and Applied Geophysics, doi: 10.1007/s00024-014-0983-8.

Gusman, A. R., Y. Tanioka, B. T. MacInnes, H. Tsushima, (2014), A methodology for near‐field tsunami inundation forecasting: Application to the 2011 Tohoku tsunami, Journal of Geophysical Research: Solid Earth 119 (11), 8186-8206, doi: 10.1002/2014JB010958.

Tanioka, Y., A. R. Gusman, K. Ioki, Y. Nakamura, (2014), Real-time tsunami inundation forecast for a recurrence of 17th century Great Hokkaido Earthquake in Japan, J. Disaster Research, 9, 3, 358-364.

Gusman, A. R., and Tanioka, Y., (2013), W phase inversion and tsunami inundation modeling for tsunami early warning: case study for the 2011 Tohoku event, Pure and Applied Geophysics, doi: 10.1007/s00024-013-0680-z.

MacInnes, B. T., A. R. Gusman, R. J. LeVeque, Y. Tanioka, (2013), Comparison of earthquake source models for the 2011 Tohoku event using tsunami simulations and near field observations, Bulletin of the Seismological Society of America, 103, 2B, 1256–1274, doi: 10.1785/0120120121

Gusman, A. R., M. Fukuoka, Y. Tanioka, (2013), Effect of the largest foreshock (Mw 7.3) on triggering the 2011 Tohoku earthquake (Mw 9.0), Geophysical Research Letters, 40, 497-500, doi:10.1002/grl.50153.

Gusman A. R., Y. Tanioka, and T. Takahashi, (2012), Numerical experiment and a case study of sediment transport simulation of the 2004 Indian Ocean tsunami in Lhok Nga, Banda Aceh, Indonesia, Earth Planets and Space, 64, 817-827, doi: 10.5047/eps.2011.10.009.

Tanioka, Y., A. R. Gusman, (2012), Reexamination of occurrence of large tsunamis after the analysis of the 2011 Great Tohoku-oki earthquake, 64, 265-270. (In Japanese)

Gusman A. R., Y. Tanioka, S. Sakai, and H. Tsushima, (2012), Source model of the 2011 great Tohoku earthquake estimated from tsunami waveforms and crustal deformation data, Earth and Planetary Science Letters, 341-344, 234-242, doi: 10.1016/j.epsl.2012.06.006.

Satake, K., Y. Nishimura, P. Putra, A. R. Gusman, Y. Tanioka, Y. Fujii, H. Sunendar, H. Latief, and E. Yulianto, (2012), Tsunami Source of the 2010 Mentawai, Indonesia, Earthquake Inferred from Tsunami Field Survey and Waveform Modeling, Pure and Applied Geophysics, doi: 10.1007/s00024-012-0536-y.

Kakinami, Y., M. Kamogawa, Y. Tanioka, S. Watanabe, A. R. Gusman, J-Y. Liu, Y. Watanabe, and T. Mogi, (2012), Tsunamigenic ionospheric hole, Geophysical Research Letters, 39, L00G27, doi: 10.1029/2011GL050159.

Tanioka, Y., H. Latief, H. Sunendar, A. R. Gusman, and S. Koshimura, (2012), Tsunami hazard mitigation at Palabuhanratu, Indonesia, Journal of Disaster Research, Vol. 7 No. 1, 19-25.

Moore A., J. Goff, B. G. McAdoo, H. M. Fritz, A. Gusman, N. Kalligeris, K. Kalsum, A. Susanto, D. Suteja, and C. E. Synolakis, (2011), Sedimentary deposits from the 17 July 2006 Western Java tsunami, Indonesia: use of grain size analyses to assess tsunami flow depth, speed, and traction carpet characteristics, Pure and Applied Geophysics, doi: 10.1007/s00024-011-0280-8.

Gusman A. R., Y. Tanioka, T. Kobayashi, H. Latief, and W. Pandoe, (2010), Slip Distribution of the 2007 Bengkulu Earthquake Inferred from Tsunami Waveforms and InSAR Data, J. Geophys. Res., 115, B12316, doi: 10.1029/2010JB007565.

Tanioka Y., Y. Nishimura, Y. Nakamura, K. Hirakawa, T. K. Pinegin, K. A. Ekaterina, V. V. Ponomareva, and A. R. Gusman, (2009), Tsunami deposit studies in north Kurile Islands (Paramushir and Shumshu Islands) to understand a pattern of the occurrence of great earthquakes, Earth Monthly, 31, 321 – 333. (In Japanese)

Gusman A. R., Y. Tanioka, H. Matsumoto, and S –I. Iwasaki, (2009), Analysis of the tsunami generated by the great 1977 Sumba earthquake that occurred in Indonesia, Bull. Seism. Soc. Am., 99, 2169 – 2179, doi: 10.1785/0120080324.

Namegaya Y., Y. Tanioka, K. Abe, K. Satake, K. Hirata, M. Okada and A. R. Gusman, (2009), In situ measurements of tide gauge response and corrections of tsunami waveforms from the Niigataken Chuetsu-oki earthquake in 2007, Pure appl. Geophys, 166, 97-116, doi: 10.1007/s00024-008-0441-6.

Fritz, H.M., W. Kongko, A. Moore, B. McAdoo, J. Goff, C. Harbitz, B. Uslu, N. Kalligeris, D. Suteja, K. Kalsum, V. Titov, A. Gusman, H. Latief, E. Santoso, S. Sujoko, D. Djulkarnaen, H. Sunendar, and C. Synolakis, (2007), Extreme run-up from the 17 July 2006 Java tsunami, Geophys. Res. Lett., 34, L12602, doi: 10.1029/2007GL029404.