HR: 1340h
AN: S23B-1373    [Abstracts]
TI: Using Finite-Frequency SH Wave Traveltimes and Amplitudes to Image Upper Mantle SH Velocity and Attenuation Structure in Western US
AU: * Tian, Y
EM: ytian@princeton.edu
AF: Princeton University, Department of Geosciences, Guyot Hall, Princeton, NJ 08544, United States
AU: Nolet, G
EM: nolet@princeton.edu
AF: Princeton University, Department of Geosciences, Guyot Hall, Princeton, NJ 08544, United States
AU: Sigloch, K
EM: sigloch@princeton.edu
AF: Princeton University, Department of Geosciences, Guyot Hall, Princeton, NJ 08544, United States
AB: In recent mantle tomographic studies, finite-frequency body-wave sensitivity kernels have been used to improve the resolution and the recovery of perturbation amplitude of 3-D heterogeneities. We present a first inversion for SH traveltimes and amplitudes measured in multiple frequency bands. Our data set contains 54294 acceptable traveltimes and amplitudes respectively, measured in 5 frequency bands with center frequencies from 0.025 to 0.4 Hz. In the current data set, about 60% of the data are from US Array and US stations. Data consistency has been confirmed by similar traveltime (amplitude) patterns between close event pairs, and by the correlation between traveltime anomaly pattern and tectonic structures, both globally (in North America and Western Europe) and regionally (along the RISTRA array). The observed traveltime dispersion is on the order of 0.8s. The difference between relative amplitude anomalies (w.r.t. predicted amplitudes) in different frequency bands is on the order of 25%. The multiple-frequency-band data provide higher tomographic resolution because the sensitivity of banana-doughnut kernels is dependent on the frequency content of the waveform. The observed frequency-dependence of the data suggests that some of the heterogeneity is of a length scale comparable to the Fresnel zone. A preliminary inversion result using traveltimes alone shows clearly visible division between slow upper mantle in Western US and higher velocities in Central and Eastern US, though the fact that the data set is limited to teleseismic S waves prevents an accurate depth estimate for high-velocity root. Some details visible in the western US region with dense (US Array) station coverage will be discussed. We also expect to be able to present finite-frequency velocity and attenuation models of the upper mantle in Western US obtained from a simultaneous inversion of traveltime and amplitude data.
DE: 7203 Body waves
DE: 7208 Mantle (1212, 1213, 8124)
DE: 7270 Tomography (6982, 8180)
SC: Seismology [S]
MN: 2007 Fall Meeting