HR: 1330h
AN: U53A-08    [Abstracts]
TI: Constraints on Source Rupture From the Directivity of P Waves Excited by the 2004 Sumatra-Andaman Megathrust
AU: * Baltay, A
EM: annemarie.baltay@yale.edu
AF: Dept. of Geology and Geophysics Yale University, PO Box 208109, New Haven, CT 06520-8109 United States
AU: Park, J
EM: jeffrey.park@yale.edu
AF: Dept. of Geology and Geophysics Yale University, PO Box 208109, New Haven, CT 06520-8109 United States
AB: The rupture of the 2004 Sumatra-Andaman megathrust progressed from southeast toward the northwest, starting offshore central Sumatra and ending near the northern extreme of the Andaman Island chain. From the duration of large amplitude P wave energy highpassed at 1 Hz, the primary rupture appears to have lasted 400-500 s, long enough for the P wave to overlap with the PP and PPP body phases in observed seismic records. Source directivity causes the apparent rupture duration to vary from station to station, shorter for source azimuths aligned with rupture propagation (i.e. to the NW) and longer for source azimuths opposed to the rupture propagation. Using body wave data from stations of the Global Seismographic Network (GSN), Geoscope, GEOFON, Mednet and other broadband seismic stations, we examine the details of source directivity using body waves. We apply multiple-taper spectrum analysis to estimate the coherence of body wave signals recorded at different stations, on the assumption that correlated waveform features represent source effects, not site effects. Doppler shifts associated with rupture directivity should be manifest as coherence peaks at mismatched frequencies. We will examine whether rupture directivity exhibits detectable variation in different intervals of the source rupture.
DE: 7203 Body wave propagation
DE: 7209 Earthquake dynamics and mechanics
DE: 7215 Earthquake parameters
DE: 9340 Indian Ocean
SC: Union [U]
MN: 2005 Joint Assembly