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The Portability of Some Regional Seismic Discriminants and Related Broadband Waveform Modeling,

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We are investigating the portability of regional seismic discriminants which were developed from the analysis of data for southwestern U.S. earthquakes and NTS explosions. Besides determining whether or not these discriminants are effective for seismic events in other tectonically active regions, it will be possible to calibrate the effective discriminant parameters for these different regions, so that an event from any such area can be incorporated into a unified database. Events studied are the U.S. PNEs and earthquakes in the Colorado PlateauRockies region, explosions at the Kazaldi CIS and Lop Nor PRC test sites, as well as earthquakes in and around this region of Asia. Events in Pakistan are analyzed by these discriminants, too, although no explosion data are available. This region includes significant deep seismicity d50km. The discriminants being used here are the ratio of integrated short-period P-wave to long-period energy predominantly surface wave summed over the three components sp sub z-Plp sub 3, the ratio of integrated short-period vertical component energy between the P and S wavetrains sp sub z-Psp sub z-S, and the ratio of M sub L to scalar seismic moment M sub 0. For the Colorado Plateau data set the energy ratio discriminants were modified to use peak amplitudes, as many of the records could not be digitized. The sp sub z-Plp sub 3 discriminant is most effective at distinguishing source-types. The sp sub z-Psp sub z-S energy ratio appears to be useful to identify deep events from shallower crustal earthquakes. The M sub LM sub 0 discriminant is deterministic, requiring Greens functions that reflect the crustal structure of a region with which to invert waveform data to obtain the source parameters for any event.

Subject Categories:

  • Government and Political Science
  • Seismology
  • Seismic Detection and Detectors
  • Nuclear Weapons

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