HR: 0830h
AN: U51B-0006    [PDF]
TI: Small-scale structure of the core-mantle boundary beneath four regions of the Pacific and Indian Ocean
AU: * Rost, S
EM: srost@es.ucsc.edu
AF: Arizona State University, Department of Geological Sciences Box 871419, Tempe, AZ 85287-1404 United States
AU: Garnero, E
EM: garnero@asu.edi
AF: Arizona State University, Department of Geological Sciences Box 871419, Tempe, AZ 85287-1404 United States
AU: Revenaugh, J
EM: justinr@umn.edu
AF: University of Minnesota, Department of Geology and Geophysics 310 Pillsbury Drive SE, Minneapolis, MN 55455 United States
AB: Core reflected phases offer an unique probe to the structure of the core-mantle boundary (CMB). Using high quality, short-period array datasets, waveform modeling and amplitude information it is possible to identify structural changes in seismic wave-speeds at the CMB on very short scale-lengths of ten's of km's. Especially, the resolution of ultra-low-velocity zones at the CMB (ULVZ) can be increased tremendously using these datasets. We collected data from three small-aperture, short-period, vertical arrays in Canada (Yellowknife), Australia (Warramunga) and India (Gauribidanur). Using earthquakes from different Pacific subduction zones and core-reflected (\textit{PcP}) and converted phases (\textit{ScP}) we are able to probe the CMB in different locations around the Pacific and Indian ocean that have not been probed for CMB structure with high-resolution before. We find a multitude of different structures including ULVZ, core-rigidity zones, scattering and possible CMB topography, but also regions where the data indicates a simple (IASP91-like) CMB or structure well beneath the resolution level of the short-period data. Using both \textit{P}-wave and \textit{S}-wave data we are able to set better constraints on possible generation mechanisms of ULVZ than is possible with diffracted phases like \textit{SP$_{\mathit{diff}}$KS}. A comparison with large-scale studies will help us to better understand the dynamics of the core-mantle boundary.
DE: 7200 SEISMOLOGY
DE: 7207 Core and mantle
SC: U
MN: 2003 Fall Meeting