HR: 1340h
AN: S53B-0228 [Abstracts]
TI: Small Scale Lower-Mantle Structure as Revealed by SPdKS Back-Azimuth and Slowness
Deviations
AU: * Bull, A L
EM: abigail.bull@asu.edu
AF: Arizona State University, Department of Geological Sciences, Arizona State University, Tempe, AZ
85287-1404
United States
AU: Garnero, E
EM: garnero@asu.edu
AF: Arizona State University, Department of Geological Sciences, Arizona State University, Tempe, AZ
85287-1404
United States
AU: Rost, S
EM: srost@asu.edu
AF: Arizona State University, Department of Geological Sciences, Arizona State University, Tempe, AZ
85287-1404
United States
AU: Thomas, C
EM: tine@liverpool.ac.uk
AF: University of Liverpool, Department of Earth Sciences, University of Liverpool, 4 Brownlow Street,
Liverpool, L69 3GP
United Kingdom
AB:
Back azimuth and slowness deviations of the seismic phase SPdKS are used to investigate small to large-scale velocity
heterogeneity in the lower mantle and at the core-mantle boundary (CMB). SPdKS is the result of an SKS wave with an angle of
incidence to the CMB equal to the critical angle for ScP, and initiates near 110 degrees. SPdKS has a small segment of P-wave
diffraction along the mantle-side of the CMB, at the SKS core entry and exit location. SKS and SPdKS have very similar paths
through the mantle. Global data were collected from the IRIS database for deep events at broadband networks with apertures
of a few hundreds of kilometers. The array approach allows enhancement of resolution of key wavefield information. For
example, the horizontal slowness and back azimuth of SKS and SPdKS can be accurately measured. Recent studies have presented
models that should result in deviations from the theoretical great-circle plane containing the stations and earthquake. Here,
we present horizontal slowness and back azimuth anomalies of SKS and SPdKS, which offer valuable insight into deep mantle
structure. Observed back azimuth anomalies can be significant; preliminary analyses suggest the SPdKS back azimuth can be off
by as much as 5 deg. We will present results for several key regions, including anomalies associated with superplume
provinces.
DE: 7207 Core and mantle
SC: Seismology [S]
MN: 2004 AGU Fall Meeting