HR: 0800h
AN: U11A-0807    [Abstracts]
TI: Tsunami Source Model of the 2004 Sumatra-Andaman Earthquake inferred from Tide Gauge and Satellite Data
AU: * Fujii, Y
EM: fujii-y@aist.go.jp
AF: Active Fault Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan
AU: Satake, K
EM: kenji.satake@aist.go.jp
AF: Active Fault Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan
AB: The tsunami generation process of the 2004 Sumatra-Andaman earthquake were estimated from the tsunami waveforms recorded on tide gauges and sea surface heights captured by satellite altimetry measurements over the Indian Ocean. The earthquake (0:58:53, 26, Dec., 2004, UTC), the largest in the last 40 years, caused devastating tsunami damages to the countries around the Indian Ocean. One of the important questions is the source length; the aftershocks were distributed along the Sunda trench for 1000 to 1200 km, from off northwestern part of Sumatra island through Nicobar islands to Andaman island, while seismic wave analyses indicate much shorter source length (several hundred km). We used instrumental data of this tsunami, tide gauges and sea surface heights. Tide gauge data have been collected by Global Sea Level Observing System (GLOSS). We have also used another tide gauges data for tsunami simulation analysis. Tsunami propagation was captured as sea surface heights of Jason-1 satellite altimetry measurements over the Indian Ocean for the first time (Gower, 2005). We numerically compute tsunami propagation on actually bathymetry. ETOPO2 (Smith and Sandwell, 1997), the gridded data of global ocean depth from bathymetry soundings and satellite gravity data, are less reliable in the shallow ocean. To improve the accuracy, we have digitized the charts near coasts and merged the digitized data with the ETOPO2 data. The long-wave equation and the equation of motion were numerically solved by finite-difference method (Satake, 1995). As the initial condition, a static deformation of seafloor has been calculated using rectangular fault model (Okada, 1985). The source region is divided into 22 subfaults. We fixed the size and geometry of each subfault, and varied the slip amount and rise time (or slip duration) for each subfault, and rupture velocity. Tsunami waveforms or Greens functions for each subfault were calculated for the rise times of 3, 10, 30 and 60 minutes. Rupture velocities were varied for 0.7, 1.7 and 2.5 km/s. Forward modeling indicates that the best fits between the observed and computed waveforms were obtained in the case of rupture velocity 1.7 km/s and rise time 3 minutes. The slip was large in the southern part of the source region.
DE: 0545 Modeling (4255)
DE: 0560 Numerical solutions (4255)
DE: 4255 Numerical modeling (0545, 0560)
DE: 4564 Tsunamis and storm surges
DE: 7240 Subduction zones (1207, 1219, 1240)
SC: Union [U]
MN: Fall Meeting 2005