Estimates Of Pn And Sn Across Eurasia

As an intermediate step to producing a integrated P and S model of the crust and upper mantle beneath most of Eurasia to predict regional station specific travel time correction surfaces, we present maps of isotropic Pn and Sn velocities across Eurasia. These maps are constructed using a groomed version of the ISC/NEIC data that are described, in part, by Engdahl et al. (1998). The locations and origin times of the events are replaced with local ground truth locations whenever possible (e.g., Sultanov et al., 1999). We use the tomographic method of Barmin et al. (2000) to estimate Pn and Sn maps on a 1.5 x 1.5 degree grid, augmented to include station and event static corrections and an epicentral distance or range correction. The starting model is CRUST5.1 (Mooney et al., 1998). We call the Pn and Sn maps together with these corrections the CU Pn=Sn model. Data are used in the inversion if the residual relative to the prediction from the spherical model AK135 (Kennett et al., 1995) is less than 7.5 s for P and 15 s for S, if the event depth is within the crust or less than 50 km deep, if the azimuthal gap to all reporting stations for the event is less than 180 degrees, and if the nominal error ellipse is less than 1000 km2 in area. We define the phases Pn and Sn as arriving between epicentral distances of 3 and 15 degrees. The resulting data set consists of about 1,600,000 Pn and 400,000 Sn travel times inhomogeneously distributed across Eurasia.
Proceedings of the 22nd Annual DoD/DOE Seismic Research Symposium: Planning for Verification of and Compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT) held in New Orleans, Louisiana on September 13-15, 2000. U.S. Government or Federal Rights. The original document contains color images.