Tsunami waveform inversion of the 2007 Bengkulu, southern Sumatra earthquake

HR: 17:00h
AN: U54A-05 [Abstracts]
TI: Tsunami waveform inversion of the 2007 Bengkulu, southern Sumatra earthquake
AU: Fujii, Y
EM: fujii@kenken.go.jp
AF: International Institute of Seismology and Earthquake Engineering, Building Research Institute, Tsukuba, 305-0802, Japan
AU: * Satake, K
EM: kenji.satake@aist.go.jp
AF: Geological Survey of Japan, AIST, Tsukuba, 305-8567, Japan
AB: We have performed tsunami waveform inversion for the 2007 Bengkulu, southern Sumatra earthquake on September 12, 2007 (4.520°S, 101.374°E, Mw=8.4 at 11:10:26 UTC according to USGS), and found that the large slips were located on deeper part (> 20 km) of the fault plane, more than 100 km from the trench axis. The deep slip might have contributed the relatively small tsunami for its earthquake size. The largest slips more than 6 m were located beneath Pagais Islands, about 100-200 km northwest of the epicenter. The obtained slip distribution yields a total seismic moment of 3.6 × 10²¹ Nm (Mw = 8.3). The tsunami generated by this earthquake was recorded at many tide gauge stations located in and around the Indian Ocean. The DART system installed in deep ocean and maintained by Thai Meteorological Department (TMD) also captured this tsunami. We have downloaded the tsunami waveforms at 16 stations from University of Hawaii Sea Level Center’s (UHSLC) and National Oceanic & Atmospheric Administration’s (NOAA) web sites. The observed tsunami records indicate that the tsunami amplitudes were less than several tens of cm at most stations, around 1 m at Padang, nearest station to the source, and a few cm at DART station. For the tsunami waveforms inversion, we divided the source area (length: 250 km, width: 200 km) into 20 subfaults. Tsunami waveforms from each subfault (50 km × 50 km) or Greens functions were calculated by numerically solving the linear shallow-water long-wave equations. We adopted the focal mechanism of Global CMT solution (strike: 327°, dip: 12°, rake: 114°) for each subfault, and assumed a rise time of 1 min. The computed tsunami waveforms from the estimated slip distribution explain the observed waveforms at most of tide gauges and DART station.
UR: http://iisee.kenken.go.jp/staff/fujii/TsunamiTop.html
DE: 4564 Tsunamis and storm surges
DE: 7215 Earthquake source observations (1240)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
DE: 9320 Asia
SC: Union [U]
MN: 2007 Fall Meeting