HR: 14:00h
AN: S33A-03 INVITED     [Abstracts]
TI: Pre-Stack Kirchhoff Depth Migrated Images of the Upper Mantle
AU: * Levander, A
EM: alan@rice.edu
AF: Earth Science, Rice University, 6100 Main Street, Houston, TX 77005 United States
AU: Niu, F
EM: fniu@rice.edu
AF: Earth Science, Rice University, 6100 Main Street, Houston, TX 77005 United States
AU: Ham, S
EM: telnet2u@rice.edu
AF: Earth Science, Rice University, 6100 Main Street, Houston, TX 77005 United States
AB: We present images made from receiver function data recorded in three different upper mantle tectonic regimes: the Kaapvaal craton, the Japanese subduction zone, and the Jemez Lineament of the western U.S. orogenic plateau. The seismic data are migrated using a 2.5 D prestack Kirchhoff depth migration algorithm that uses 2-D seismic velocity models developed from tomography as the migration velocity models. The Kaapvaal craton image has been made from 9 earthquakes recorded along a 2000 km long array. Both of the transition zone discontinuities stand out very clearly. The amplitudes and thicknesses of the discontinuities estimated from the image are in agreement with predictions of global reference models. Above the transition zone are a number of events extending 100's of kilometers as slab-like structures which may form the bottom of the Kaapvaal craton. In Japan we make use of a number of earthquakes recorded at the very dense Hi-Net array, which consists of more than 500 borehole seismographs. The migrated receiver function images show the transition zone discontinuities very clearly, as well as the slab subducting beneath Hokkaido. The uplift predicted by slab penetratation of the 410 discontinuity is clearly seen in the migrated image. The slab appears to stall above the 660 discontinuity. Across the Jemez lineament, an image made from 7 earthquakes recorded at a 225 km long seismic array shows a complex set of upper mantle sill-like structures extending from the Moho to a depth of about 125 km. From active source seismic data we estimate that the upper mantle contains about 1 percent partial melt. Amplitudes in the receiver function image suggest that this is true in all the sill structures in the upper mantle. We relate the sill structures to recent volcanism and uplift along the lineament.
DE: 0905 Continental structures (8109, 8110)
DE: 0935 Seismic methods (3025)
DE: 7218 Lithosphere and upper mantle
DE: 8110 Continental tectonics--general (0905)
SC: Seismology [S]
MN: 2005 Joint Assembly