HR: 1340h
AN: S53A-1033    [Abstracts]
TI: Array Analysis of T-Waves Generated by Large Tsunamigenic and Non-tsunamigenic Earthquakes
AU: * Pulli, J J
EM: jpulli@bbn.com
AF: BBN Technologies, 1300 North 17th Street Suite 400, Arlington, VA 22209, United States
AU: Salzberg, D H
EM: david.h.salzberg@saic.com
AF: Science Applications International Corp., 1710 SAIC Drive M/S 1-11-15, McLean, VA 22102, United States
AB: Hydroacoustic stations of the International Monitoring System are now operating in the Atlantic, Pacific and Indian Oceans. Each station consists of one or two three-element arrays with a bandwidth of 100 Hz and precise signal direction finding capability on the order of 0.25 degrees. These arrays routinely record T-waves generated by sub- sea earthquakes and provide the capability to localize the points of sound generation on the ocean floor. The utility of these arrays for understanding T-wave generation was demonstrated with data from the Great Sumatran Earthquake of December 26, 2004, where T-waves of 15-minutes in time and nearly 1000-km in source extent could be localized along the Sumatran trench. This correlates well with seismic determinations of the fault dynamics and implies the capability to perform real-time estimates of source complexity, which impacts tsunami warning. Since then, we have applied array-processing techniques to the analysis of T-waves from dozens of sub-sea earthquakes in the Atlantic, Pacific and Indian Oceans. Here we report on a comparison of results from the larger events in our dataset (magnitudes > 6.5 Mw), some of which have generated recordable or reportable tsunamis. These include: March 28, 2005 Northern Sumatra, Mw 8.6; May 16, 2006 Northern Sumatra, Mw 6.8; March 30, 2007 Kamchatka, Mw 6.5; and August 15, 2007 Coastal Peru, Mw 8.0. T-waves from all of these events can be localized to an extended source area, which is often more than 100-km long, but the relationship of this source area to tsunamigenisis is complicated. This source area may or may not be directly indicative of the fault zone extent, since T-wave generation results from a complex interaction seismic waves with ocean bottom topography. This interaction must be accounted for to relate acoustic source area to seismic faulting. One way to accomplish this is by using smaller events (aftershocks) as Green's functions for the main shock. Array analysis of T-waves from aftershocks often show acoustic excitation patterns that mimic those of the main shock. Addition factors related to tsunamigensis include spectral content and source duration.
DE: 4259 Ocean acoustics
DE: 4564 Tsunamis and storm surges
DE: 7215 Earthquake source observations (1240)
DE: 7240 Subduction zones (1207, 1219, 1240)
SC: Seismology [S]
MN: 2007 Fall Meeting