[J09-P] Poster

[J09-P-06] Updating Hypocenter Location around Indonesia Region Derived from 3D Seismic Velocity Structure: Time Period of April 2009-July 2016

^○Andri Dian Nugraha¹, Hasbi Ash Shiddiqi¹, Sri Widiyantoro¹, Shindy Roslia¹, Mohamad Ramdhan^1,2, Wandono Wandono², Daryono Daryono², Samsul Wiyono², Mahsyur Irsyam¹ (1.Institut Teknologi Bandung, Bandung, Indonesia, 2.Agency for Meteorology, Climatology and Geophysics (BMKG), Jakarta, Indonesia)

We conducted hypocenter relocation of ~40,000 events (Magnitude of 1.4 to 8.5) recorded by 451 stations around and outside Indonesia region that compiled by Indonesian Meteorology, Climatology, and Geophysics Agency (BMKG) from April 2009 to July 2016. We used teleseismic double-difference relocation inversion including local, regional and teleseismic arrival time data. Our previous study of 3D seismic velocity model beneath the Indonesian region with grid size 1o by 1o and the 1D seismic velocity model were used for the regions inside and outside Indonesia region, respectively. This method improved limitation from BMKG earthquake data catalog in which events were recorded from scattered seismic station array and insufficient azimuthal gap around Indonesia. Our results show that travel-time RMS residuals were greatly reduced compared to those of the BMKG catalog. Seismicity at shallower depth (less than 50 km) shows significant improvement, refining shallow geological structures, e.g. trench and major strike slip faults. Clustered seismicity is also detected beneath volcanic regions, and probably related to volcano activities and also major faults nearby. Beneath Western Sunda arc, Wadati-Benioff Zone (WBZ) extents to 300 km and it depicts gently dipping slab beneath this region. The WBZ beneath Eastern Sunda Arc is extent deeper to 500 km and depicts steep slab geometry. At Sunda-Banda transition zone, we found anomalously low seismicity beneath oceanic-continental transition region. WBZ of highly curvature Banda arc extents to 600 km and depicts two-slab model. In Molucca collision zone, seismicity from this region clearly shows two-slab of Halmahera plate: east- and west-dipping slab. Furthermore, we used global centroid moment tensor catalog where data available for earthquakes with magnitude 6 or greater. Mostly, focal mechanism solution for large earthquakes around this region are thrust mechanism that related to subduction processes.