HR: 13:40h
AN: T23F-01    [Abstracts]
TI: A Eurasian and North African Crust and Upper Mantle Model for Regional Seismic Location
AU: * Myers, S C
EM: smyers@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Ave. Box 808 L205, Livermore, CA 94551, United States
AU: Ballard, S
AF: Sandia National Laboratory, PO Box 5800, Albuquerque, NM 87185,
AU: Rowe, C
AF: Los Alamos National Laboratory, 1350 Central, MS C330, Los Alamos, NM 87545,
AU: Wagner, G
AF: Air Force Technical Applications Center, 1030 S. Highway A1A, Patrick AFB, FL 32925, United States
AU: Antolik, M
AF: Quantum Technology Sciences, Inc, 1980 North Atlantic Avenue, Suite 930, Cocoa Beach, FL 32931, United States
AU: Hutchenson, K
AF: Quantum Technology Sciences, Inc, 1980 North Atlantic Avenue, Suite 930, Cocoa Beach, FL 32931, United States
AU: Phillips, W S
AF: Los Alamos National Laboratory, 1350 Central, MS C330, Los Alamos, NM 87545,
AU: Ramirez, A
AF: Lawrence Livermore National Laboratory, 7000 East Ave. Box 808 L205, Livermore, CA 94551, United States
AU: Begnaud, M
AF: Los Alamos National Laboratory, 1350 Central, MS C330, Los Alamos, NM 87545,
AU: Pasyanos, M
AF: Lawrence Livermore National Laboratory, 7000 East Ave. Box 808 L205, Livermore, CA 94551, United States
AU: Dodge, D
AF: Lawrence Livermore National Laboratory, 7000 East Ave. Box 808 L205, Livermore, CA 94551, United States
AU: Flanagan, M
AF: Lawrence Livermore National Laboratory, 7000 East Ave. Box 808 L205, Livermore, CA 94551, United States
AU: Dwyer, J
AF: Air Force Technical Applications Center, 1030 S. Highway A1A, Patrick AFB, FL 32925, United States
AU: Russell, D
AF: Air Force Technical Applications Center, 1030 S. Highway A1A, Patrick AFB, FL 32925, United States
AB: We are developing a velocity model of the crust and upper mantle across Eurasia and North Africa to reduce event location error by improving regional travel-time prediction accuracy. The model includes both P and S velocities, enabling prediction of Pn, Pg, Sn, and Lg phases. Here, we report on the Pn travel-time prediction effort. The model parameterization is a global tessellation, which allows extensibility beyond the current focus area, with node spacing of approximately 1°. The model is defined on a WGS84 ellipsoid that includes topography, thus eliminating the need for conventional corrections to base model travel-time calculations. A velocity profile with depth is defined at each node that includes a crustal stack, mantle velocity at the Moho (Pn velocity), and a linear mantle gradient term. Parameterizing mantle velocity structure with a linear term allows computation of Pn and Sn travel times in approximately one millisecond, which is needed for real-time seismic location. Velocity and mantle gradient at arbitrary points can be calculated by interpolating values at nodes. The starting model is a geophysical compilation that constrains Moho depth and depths of crustal layers, as well as best estimates for crust and mantle velocities. The starting model itself is demonstrated to improve travel-time prediction over iasp91, and we use a tomographic method to further refine Pn velocity, mantle gradient, and a node-specific crustal slowness. Our tomographic data set consists of approximately 3.5 million regional arrivals from events that meet criteria that ensure location accuracy. Non-seismic constraints on event location are used when available. Each datum is tested to meet strict quality control standards that include comparison with established distance-dependent travel-time residual populations relative to the iasp91 model. In addition to bulletin measurements, nearly 12,000 arrival measurements were made at the national laboratories. This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.
DE: 1209 Tectonic deformation (6924)
DE: 1219 Gravity anomalies and Earth structure (0920, 7205, 7240)
DE: 7205 Continental crust (1219)
DE: 7218 Lithosphere (1236)
DE: 9320 Asia
SC: Tectonophysics [T]
MN: 2007 Fall Meeting