HR: 16:00h
AN: U44A-03    [Abstracts]
TI: Ground motion excited by the Tsunami of 26 December 2004: Implications for tsunami warning
AU: * Shen, Y
EM: yshen@gso.uri.edu
AF: University of Rhode Island, South Ferry Road, Narragansett, RI 02882 United States
AB: Approximately 70 minutes after the great Sumatra-Andaman Islands earthquake of 26 December 2004 and 40 to 130 minutes before the tsunami's arrival, the ground at three island stations in the Indian Ocean started to shake at periods comparable to those of the tsunami waves (~1000 s). The characteristics and timing of these very-long period waves are not those of the normal seismic phases generated by earthquakes, and strongly suggest ground deformation excited by the tsunami waves in a way similar to the generation of seismic waves by the oscillation of a heavy mass pressed against the ground, a technique often used in geophysical exploration. The arrival times of these anomalous waves are consistent with the paths of tsunami-excited seismic waves, along which the tsunami slammed into the east coast of the Indian Ocean and generated seismic waves, which then propagated in the solid earth at a velocity higher than that of the tsunami to the stations in the Indian Ocean. The observation of the same very-long period wave at Hainan, China, at the time expected for the tsunami-excited seismic waves to propagate from the west coast of northern Sumatra, reconfirms our interpretation. We can rule out the possibility that the anomalous long-period waves are the fundamental-mode wave and overtones propagating along the major arcs, because the predicted times are opposite to the observation. Additional studies are required to further understand the coupling between tsunami waves and the solid earth and the manner in which that knowledge might be used to reduce the loss and suffering in future tsunamis.
DE: 4223 Descriptive and regional oceanography
DE: 4564 Tsunamis and storm surges
DE: 7205 Continental crust (1242)
DE: 7223 Seismic hazard assessment and prediction
SC: Union [U]
MN: 2005 Joint Assembly