HR: 0800h
AN: S41C-1016    [Abstracts]
TI: Lateral Variation of Velocity Discontinuities in the Lowermost Mantle Under the Cocos Plate
AU: * Kito, T
EM: t.kito@liverpool.ac.uk
AF: University of Liverpool, Departmet of Earth and Ocean Sciences, 4 Brownlow Street, Liverpool, L69 3GP United Kingdom
AU: Rost, S
EM: srost@asu.edu
AF: Arizona State University, Department of Geological Sciences, Tempe, Phoenix, AZ 85287-1404 United States
AU: Thomas, C
EM: tine@liverpool.ac.uk
AF: University of Liverpool, Departmet of Earth and Ocean Sciences, 4 Brownlow Street, Liverpool, L69 3GP United Kingdom
AU: Garnero, E J
EM: garnero@asu.edu
AF: Arizona State University, Department of Geological Sciences, Tempe, Phoenix, AZ 85287-1404 United States
AB: A double Array Method (DAM) and Migration method have been used to delineate the lateral variation of the discontinuities in the lowermost mantle under the Cocos Plate. We used P and S waves from deep and intermediate earthquakes in South America recorded at Californian broadband network stations. For the DAM, the data were deconvolved by the P and S beams for each event to get rid of the source time function so that all events can be stacked simultaneously. Subsequently, a band-pass filter of 1-10 s was applied for P waves and a low-pass filter at 0.3 Hz for S waves. We set bins to cover the PcP and ScS reflection points and the sizes of bins are 4 degrees of latitude for P waves and 2 degrees for S waves. The bins are shifted by 1 degree overlapping from the south to the north. We detect P wave velocity anomalies in this region where up to now mainly S wave observations have been reported. The topography observed in P wave essentially follows the one reported in S wave using the migration method.The P and S wave velocity discontinuties detected by the DAM are essentially consistent, although the form of the discontinuities depends on the frequency bands. The discontinuities in the southern part of our study area tend to be deeper than those in the northern part undulating from 2550 km to 2700 km depths both in P and S waves. This may indicate the top of the dense subducted slab or the recently discovered post-perovskite structure deep mantle phase change.
DE: 1212 Earth's interior: composition and state (7207, 7208, 8105, 8124)
DE: 1213 Earth's interior: dynamics (1507, 7207, 7208, 8115, 8120)
DE: 7203 Body waves
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
SC: Seismology [S]
MN: Fall Meeting 2005