HR: 17:35h
AN: S44B-06    [Abstracts]
TI: What can we Learn From the December 26, 2004 Sumatra Earthquake to Improve Tsunami Hazard Assessment Models?
AU: * Geist, E L
EM: egeist@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., MS 999, Menlo Park, CA 94025 United States
AU: Titov, V V
EM: vasily.titov@noaa.gov
AF: NOAA/PMEL - UW/JISAO, 7600 Sand Point Way NE, Seattle, WA 98115 United States
AU: Arcas, D
EM: diego.arcas@noaa.gov
AF: NOAA/PMEL - UW/JISAO, 7600 Sand Point Way NE, Seattle, WA 98115 United States
AU: Pollitz, F F
EM: fpollitz@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., MS 999, Menlo Park, CA 94025 United States
AU: Bilek, S L
EM: sbilek@nmt.edu
AF: New Mexico Tech, 801 Leroy Place, Socorro, NM 87801 United States
AB: The devastating Indian Ocean tsunami of 2004 arose from complex source properties of the megathrust earthquake along the Sumatra-Andaman subduction zone. As we progress in our understanding of the only M>9 earthquake recorded by modern seismic and geodetic instruments, we look toward improving tsunami hazard assessment models. Standard models often use a simplified source description: instantaneous, uniform slip along one to several sub-faults. For calculating tsunami amplitudes in the far-field and for smaller earthquakes, this is often an adequate approximation. However, for calculating near-field tsunami amplitudes associated with great subduction-zone earthquakes, slip heterogeneity in space, and perhaps time, has a strong influence. Soon after the December 26, 2004 earthquake, it was clear that there was a strong heterogeneity in the slip distribution. However, the main discrepancy between tsunami and seismologic models of the source was the overall magnitude of slip. Substantially larger amounts of slip than indicated by the seismic inversion results is needed to explain both inundation patterns and open-ocean amplitude measurements of the tsunami from satellite altimetry. This discrepancy was explained in large part by geodetic measurements of the earthquake, showing a significant component of after-slip (~25-35% of total slip). However, it is still unresolved how much slip occurred near the trench, where aftershocks suggest that the megathrust was strongly coupled. In this study, we examine the effects of both spatial and temporal heterogeneity of slip during the 2004 Sumatra earthquake on the tsunami wavefield. First, we suppose that that the slip distribution cannot be forecast and develop a suite of stochastic slip distributions all with similar average slip and M_w, constrained by the far-field tsunami model. The resulting envelope of tsunami amplitudes calculated using a 2-D finite-difference approximation to the linear long-wave equations are compared with satellite altimetry measurements. Second, we examine the slow slip phase of the earthquake to determine the time-dependent efficacy of tsunami generation. Tsunami generation models using 2-D spatial heterogeneity of both slip and rise time are also explored. The primary objective of these efforts is to develop a tsunami generation model that is consistent with strong ground-motion models and with the physics of subduction zone earthquakes.
DE: 4564 Tsunamis and storm surges
DE: 7215 Earthquake source observations (1240)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7240 Subduction zones (1207, 1219, 1240)
SC: Seismology [S]
MN: Fall Meeting 2005