Regionalized Velocity Models in Central Asia
URS GROUP INC PASADENA CA
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We have developed regional velocity models to improve the location of small seismic events near the central Asian test sites. Specifically we have used seismograms recorded by International Monitoring System IMS stations, along with ISC and Calibration Event Bulletin CEB travel-time information, to generate velocity profiles extending radially from the Lop Nor Test Site the best coverage is for the path to the northwest through the Semipalantinsk Test Site to, at the far end, the station BRVK. Most available crustal models developed for central Asia have a P velocity of 8.0 kms whereas the velocity profiles developed put Psub n in the range of 8.3-8.4 kms. Predicted travel times of P-waves traveling to the northwest of Lop Nor using these various models all yield negative residuals on the order of 2-6 seconds, suggesting these models are slower than the actual regional velocity structure. Hence, we examined a model for the Siberian Craton, the path over which these waves travel. The modified Leith model Langston, 1998 has a Moho velocity of 8.3 kms, closer to the velocities we found. Applying this model results in smaller travel-time residuals 0.5 sec. t rather than the 2-4 sec. residuals using the IASPI model, suggesting this model is more appropriate for the region. Similarly, a more appropriate model has been developed for paths to the NE and SE of Lop Nor, with a moho velocity of 8.26 kms.
- Numerical Mathematics
- Seismic Detection and Detectors