P1.7
The SIFT Tool: Validation of its Inversion Scheme and use of the Propagation Database for Tsunami Hazard Assessment
Edison Gica, JISAO/Univ. of Washington, Seattle, WA; and M. Spillane and V. V. Titov
The NOAA Center for Tsunami Research (NCTR) has developed a tool called SIFT (Short-term Inundation Forecasting for Tsunamis) to assist in Tsunami Warning Center operations during real-time events. Underlying SIFT is a database of pre-computed solutions (Gica et al., 2008) for tsunami propagation from a set of “unit” sources (100x50 km in extent, Mw = 7.5), that cover all known subduction zone and convergent plate boundaries of the Pacific, Atlantic and Indian Oceans. During an event the expanding tsunami wave front is detected in the open ocean by one or more bottom pressure sensors of the DART™ array; the data stream is telemetered via satellite. An inversion scheme identifies the linear combination of unit sources that best represents the tsunamigenic characteristics of the earthquake source. The composite propagation solution is the basis for basin-wide forecasts and provides the boundary conditions for timely, high-resolution models of inundation to assist the emergency response in the most threatened communities. Several relatively minor tsunami events in recent years have provided unplanned tests of the SIFT system and data with which to validate the assumptions on which it is based. For significant earthquakes such as the November 2006 Kuril Island event, a finite fault representation of the source, based on seismic data, is generated by USGS (USGS, 2006). With spatial resolution much finer than the 100x50km of SIFT's unit sources, it is instructive to compare tsunami hindcasts based on the finite fault source with results from the SIFT system (Figure 1.) Consistent with the findings of Titov et al. (1999), the influence of fine structure during the initial generation of the tsunami is found to be negligible in the far field. The availability of a comprehensive, credible propagation database provides opportunities for training and education, for risk assessment, and to assist in the design of the observational array. Synthetic tsunamis can simulate the risk associated with source locations and magnitudes not represented in the sparse historical record of tsunami observations, or the consequences of changes in near-shore bathymetry or infrastructure. Risk assessment is illustrated for the case of Hawai'i with sources near Atka Island in the Aleutians posing the greatest threat to the coast near Haleiwa on O‘ahu (Figure 2). Reference: Gica, E., Spillane, M.C., Titov, V.V., Chamberlin, C.D. and Newman, J.C. (2008): Development of the forecast propagation database for NOAA's Short-term Inundation Forecast for Tsunamis (SIFT), NOAA Technical Memorandum OAR PMEL-139. Titov, V.V., Mofjeld, H.O. F.I. González and Newman, J.C. (1999): “Offshore forecasting of Hawaiian Tsunamis generated in Alaska-Aleutian Subduction Zone”, NOAA Technical Memo ERL PMEL-114, PMEL. USGS (2006): 15 November 2006 Kuril event, http://earthquake.usgs.gov/eqcenter/eqinthenews/2006/usvcam/result_2/static_out
Poster Session 1, Coastal atmospheric and oceanic processes
Monday, 12 January 2009, 2:30 PM-4:00 PM, Hall 5
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