HR: 11:35h
AN: U22A-05    [Abstracts]
TI: Constraining the Rupture Length, Duration and Speed of the Great Sumatra-Andaman Earthquake Using Hydroacoustic Data
AU: * Tolstoy, M
EM: tolstoy@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964-8000 United States
AU: Bohnenstiehl, D R
EM: del@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964-8000 United States
AB: Hydroacoustic data from the International Monitoring System Diego Garcia South hydrophone station have been used to track the rupture of the Great Sumatra-Andaman Earthquake using the T-wave arrival. T-waves are generated by radiation of seismic energy at the crust-water interface, and they can travel great distances with relatively little loss in energy through a low-velocity waveguide known as the SOund Fixing and Ranging (SOFAR) channel. For this event the T-wave allows us to provide a relatively high-resolution picture of changes in the rupture speed and character. A single station approach allows topographic steering effects to be minimized. Results show that there were at least two large-scale phases of rupture with the first 180 seconds having an average speed of 2.8 km/s and the next 300 seconds having an average rupture speed of 2.1 km/s. Waveform amplitudes show two primary pulses of energy coincident with the two phases of rupture speed. Results also show that the full-length of the northern portion of the fault zone ruptured up to the latitude of the pole of rotation between the Burma and Indian Plates where subduction ends. Aftershock patterns mapped using the hydroacoustic data illustrate that in the first 30mins to few hours following the mainshock, aftershock numbers/size tracked the amplitude of waveform from the mainshock. T-wave data have the potential to address a number of fundamental questions of the rupture of this large event and also provide another tool for rapid assessment of the scale of a shallow submarine event and its tsunamigenic potential.
DE: 3025 Marine seismics (0935, 7294)
DE: 7209 Earthquake dynamics (1242)
DE: 7240 Subduction zones (1207, 1219, 1240)
SC: Union [U]
MN: Fall Meeting 2005