HR: 1340h
AN: DI53A-1097    [Abstracts]
TI: Fine Scale P-wave Structure of the Upper Mantle Discontinuities Beneath Northern Australia
AU: * Lin, P P
EM: patty.lin@asu.edu
AF: School of Earth and Space Exploration, Arizona State University, PO Box 871404, TEMPE, AZ 85287-1404, United States
AU: Garnero, E J
EM: garnero@asu.edu
AF: School of Earth and Space Exploration, Arizona State University, PO Box 871404, TEMPE, AZ 85287-1404, United States
AU: Rost, S
EM: s.rost@leeds.ac.uk
AF: Institute of Geophysics and Tectonics, School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, United Kingdom
AB: P-wave triplications arise from rapid increases in upper mantle seismic velocity with depth. Waveform analyses of the triplicated wavefield are powerful for detailed characterization of the upper mantle phase transitions, owing to their sensitivity to the size and depth of the discontinuities, as well as the under- and overlying velocity gradients. However, P-wave triplication studies are inherently more difficult than for S-waves, and hence much less common, since P-wave arrivals are typically much closer in time near the triplication crossovers than for S-waves, e.g., <1-2 sec. Here we study the P-wave field at relatively high frequency (~ 1 Hz), using the Warramunga seismic array (WRA) in Australia. WRA has an aperture of about 20 kilometers and is equipped with 20 short- period vertical instruments. We collected 1863 events between 1990 to 1994 from surrounding trenches recorded by WRA, which have an epicentral distance range roughly between 12 and 25 deg. These data mainly sample the upper mantle beneath northern Australia. We employ Nth-root stacking and fk analyses to study the triplicated waves. For each event, a master trace was computed from the 4th-root vespagram, using a sliding window that collects maximum amplitude and associated slowness information. While some master traces exhibit considerable complexity, many show clear evidence for distinctly separate upper mantle triplication phases, and provide evidence for lateral variability in upper mantle discontinuity structure, as well as heterogeneities, beneath northern Australia.
DE: 1025 Composition of the mantle
DE: 7200 SEISMOLOGY
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
DE: 9330 Australia
SC: Study of the Earth's Deep Interior [DI]
MN: 2007 Fall Meeting