HR: 1340h
AN: S13B-1066    [Abstracts]
TI: Upper-Mantle Velocity Structure Beneath Northwestern Australia From Waveforms of P, PP, S, and SS Waves
AU: * Kuge, K
EM: keiko@kugi.kyoto-u.ac.jp
AF: Department of Geophysics, Kyoto University, Sakyo, Kyoto, 606-8502 Japan
AU: Kennett, B L
EM: brian@rses.anu.edu.au
AF: Research School of Earth Sciences, Australian National University, Canberra, ACT, 0200 Australia
AB: In order to understand upper-mantle velocity structure for a region including an old continental lithosphere, we study waveforms of P, PP, S, and SS waves from shallow earthquakes around Papua New Guinea for the epicentral distance range from 10 to 45 degree. These events traverse the mantle beneath the north and west of Australia with Precambrian outcrop. The SKIPPY project with a set of deployments of portable broad-band instruments across Australia from 1993 to 1996, has been followed by further deployments by the Australian National University in the Kimberley region of north-west Australia in 1997-1998 and in Western Australia in 2000-2001. In this study, we exploit data from these deployments with a bandpass-filter between 0.03 and 0.1 Hz preceded by integration in time to obtain the displacement waveforms. Clear waveforms of P, PP, S, and SS can be observed in several record sections where the mid-points lie beneath the Arafura Sea and Northern Territory. We compute theoretical seismograms for 1-D velocity models derived from short-period travel-time data, including ak135 and the regional models njpb (Kennett et al., 1994), and az20sl3 (Kaiho and Kennett, 2000). The synthetic seismograms are compared with each other and with the corresponding observations. For S and SS waves, in addition to variations of the travel times depending on the nature of the models, differences in waveforms are expected for epicentral distances less than 20 degree and from 25 to 45 degree. For some record sections recorded in Western Australia at distances from 35 to 45 degree, we see that the njpb model, which has a thick lid of slightly high velocity, tends to match the observed waveforms better than ak135 and az20sl3.
DE: 9330 Australia
DE: 7203 Body wave propagation
DE: 7218 Lithosphere and upper mantle
SC: Seismology [S]
MN: 2004 AGU Fall Meeting