Identifikasi Sumber Patahan Gempabumi Banggai 12 April 2019 Mw 6,9 Menggunakan Data Gempabumi Susulan

Renhard Sipayung(1*), Erwan Susanto(2), Haryanta Haryanta(3),

(1) Stasiun Geofisika Banjarnegara (BMKG)
(2) Stasiun Geofisika Gowa (BMKG)
(3) Stasiun Geofisika Banjarnegara (BMKG)
(*) Corresponding Author



Abstract


Tektonik Sulawesi merupakan salah satu tatanan tektonik yang paling kompleks. Banyaknya sumber patahan dan ambiguitas mekanisme sumber seringkali menimbulkan perdebatan dalam proses identifikasi sumber patahan gempabumi di wilayah ini. Pada 12 April 2019 terjadi gempabumi merusak di daerah Banggai, Sulawesi Tengah berkekuatan 6,9 Mw. Analisis mekanisme sumber dari United States Geological Survey (USGS) menunjukkan bahwa gempabumi ini bertipe penyesaran geser dengan kedalaman centroid 19,5 km; Strike/Dip/Rake: 46/70/-172 (Bidang Nodal 1) dan Strike/Dip/Rake: 313/83/-20 (Bidang Nodal 2). Sumber patahan gempabumi ini belum terpetakan jika mengacu pada Peta Gempa Nasional 2017. Meskipun Bidang Nodal 2 dapat diasosiasikan dengan Sesar Toili yang berarah BaratLaut-Tenggara, namun hasil relokasi terhadap 114 gempabumi susulan menunjukkan tren sebaran yang lebih presisi berarah Barat Daya-Timur Laut yang sesuai dengan orientasi Sesar Peleng (sesuai dengan solusi Nodal 1). Secara vertikal gempabumi susulan tersebar pada kedalaman 5-20 km. Jika diasumsikan Sesar Peleng memanjang hingga ke lokasi mainshock maka panjang sesar yang semula 44 km menjadi 87,1 km dan magnitudo maksimum tentunya menjadi > 6,9 Mw. Hal ini berimplikasi pada adanya underestimasi bahaya seismik di daerah sekitar Banggai. Penelitian ini diharapkan dapat menjadi salah satu bahan pertimbangan kajian lanjutan untuk penilaian bahaya seismik yang lebih baik. 

Kata kunci: gempabumi susulan, relokasi, Double Difference, gempabumi Banggai, Sesar Peleng

 

Sulawesi tectonics is one of the most complicated in the world. The related faults and source mechanism ambiguity leads to earthquake source identification in debate frequently in this region. A devastating earthquake with Mw 6,9 occurred in Banggai, Central Sulawesi on 12 April 2019. The moment tensor analysis from United States Geological Survey (USGS) shows this earthquake has strike-slip mechanisms with 19.5 km depth; Strike/Dip/Rake: 46/70/-172 (Nodal Plane 1) and Strike/Dip/Rake: 313/83/-20 (Nodal Plane 2). Referring to Indonesian Seismic Sources and Seismic Hazard Maps 2017, this earthquake source still unmapped. Though the Nodal Plane 2 solution can be associated with Toili Fault which is trending in SouthEast-NorthWest direction, however, the relocation result of 114 aftershocks show the seismicity trend more precision in Southwest-Northeast direction that seemingly related to Peleng Fault (match with Nodal Plane 1). Aftershocks distribution spreads in 5 – 20 km depth vertically. If assuming Peleng Fault extends to the mainshock location, the fault length which was originally 44 km become 87.1 km and maximum magnitude increase > Mw 6.9 surely. This research is expected to be one of the considerations of further studies for better seismic hazard assessment.

Keywords: aftershocks, earthquake relocation, Double Difference, Banggai earthquake, Peleng Fault


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References


Hamilton, W. B. (1979). Tectonics of the Indonesian region (No. 1078). US Govt. Print. Off.

Garrard, R. A., & JB Supandjono, S. (1988). The geology of the Banggai-Sula microcontinent, eastern Indonesia.

Watkinson, I. M., Hall, R., & Ferdian, F. (2011). Tectonic re-interpretation of the Banggai-Sula–Molucca Sea margin, Indonesia. Geological Society, London, Special Publications, 355(1), 203-224.

Satyana, A. H., & Zaitun, S. (2016). Origins of Oils Aand Gases at Banggai–Sula Microcontinent, Eastern Sulawesi–North Moluccas: Constraints from Biomarkers and Isotope Geochemistry–Implications for Further Exploration of Cenozoic and Pre-Cenozoic Objectives.

Simandjuntak, T. O., & Barber, A. J. (1996). Contrasting tectonic styles in the Neogene orogenic belts of Indonesia. Geological Society, London, Special Publications, 106(1), 185-201.

BMKG, Press Release, 2019.

Website:https://www.bmkg.go.id/press-release/?p=gempabumi-tektonik-m-69-mengguncang-kabupaten-morowali-dan-kepulauan-banggai-berpotensi-tsunami&tag=press-release〈=ID, diakses tanggal 6 Oktober 2019.

Nasional, P. S. G. (2017). Peta sumber dan bahaya gempa Indonesia tahun 2017. Pusat Penelitian dan Pengembangan Perumahan dan Permukiman, Badan Penelitian dan Pengembangan, Kementerian Pekerjaan Umum.

USGS, Earthquake, 2019.

Website:https://earthquake.usgs.gov/earthquakes/eventpage/us700034xq/moment-tensor, diakses tanggal 6 Oktober 2019.

Valoroso, L., Chiaraluce, L., Piccinini, D., Di Stefano, R., Schaff, D., & Waldhauser, F. (2013). Radiography of a normal fault system by 64,000 high‐precision earthquake locations: The 2009 L'Aquila (central Italy) case study. Journal of Geophysical Research: Solid Earth, 118(3), 1156-1176.

Waldhauser, F., & Ellsworth, W. L. (2000). A double-difference earthquake location algorithm: Method and application to the northern Hayward fault, California. Bulletin of the Seismological Society of America, 90(6), 1353-1368.

Kennett, B. L., Engdahl, E. R., & Buland, R. (1995). Constraints on seismic velocities in the Earth from traveltimes. Geophysical Journal International, 122(1), 108-124.

Sunardi, B., Rohadi, S., Masturyono, M., Widiyantoro, S., Sulastri, S., Susilanto, P., ... & Setyonegoro, W. (2012). Relokasi Hiposenter Gempabumi Wilayah Jawa Menggunakan Teknik Double Difference. Jurnal Meteorologi dan Geofisika, 13(3).

Waldhauser, F. (2001). hypoDD--A program to compute double-difference hypocenter locations.

Goldstein, P., Dodge, D., Firpo, M., Minner, L., Lee, W. H. K., Kanamori, H., ... & Kisslinger, C. (2003). SAC2000: Signal processing and analysis tools for seismologists and engineers. The IASPEI International Handbook of Earthquake and Engineering Seismology, 81, 1613-1620.

Wessel, P., & Smith, W. H. (1998). New, improved version of Generic Mapping Tools released. Eos, Transactions American Geophysical Union, 79(47), 579-579.

Wells, D. L., & Coppersmith, K. J. (1994). New empirical relationships among magnitude, rupture length, rupture width, rupture area, and surface displacement. Bulletin of the seismological Society of America, 84(4), 974-1002.

Dziewonski, A. M., Chou, T. A., & Woodhouse, J. H. (1981). Determination of earthquake source parameters from waveform data for studies of global and regional seismicity. Journal of Geophysical Research: Solid Earth, 86(B4), 2825-2852.

Ekström, G., Nettles, M., & Dziewoński, A. M. (2012). The global CMT project 2004–2010: Centroid-moment tensors for 13,017 earthquakes. Physics of the Earth and Planetary Interiors, 200, 1-9.

Meilano, I., Abidin, H. Z., Andreas, H., Gumilar, I., Sarsito, D., Rahma Hanifa, R., ... & Fukuda, Y. (2012). Slip rate estimation of the Lembang Fault West Java from geodetic observation. Journal of Disaster Research, 7(1), 12-18.

Marliyani, G. I. (2016). Neotectonics of Java, Indonesia: Crustal deformation in the overriding plate of an orthogonal subduction system. Arizona State University.


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