Accession Number : ADP204421

Title :   Isotropic and Deviatoric Moment Inversion of Regional Surface Waves from Nevada Test Site Explosions: Implications for Yield Estimation and Seismic Discrimination,

Corporate Author : CALIFORNIA INST OF TECH PASADENA SEISMOLOGICAL LAB

Personal Author(s) : Woods, Bradley B. ; Harkrider, David G.

PDF Url : ADP204421

Report Date : 14 AUG 1995

Pagination or Media Count : 8

Abstract : Seismic moments of Nevada Test Site (NTS) explosions were determined from regional surface wave spectra. Two methods were used. In one the moment is solved for assuming only an explosive source, or average scalar moment; in the other a joint inversion for an isotropic (explosive) source plus a constrained double couple moment component representing tectonic strain release (TSR). Although the general moment tensor solution to this joint inversion problem is non-unique, if some assumptions are made concerning the non-isotropic moment components, then the remaining source parameters can be solved by a linear least-squares inversion scheme. We examined the errors in determining the isotropic moment component (M sub I) by this latter method of constrained linear inversion solutions in a canonical study using a theoretical network of long-period (6-60 sec.) surface wave data. The network azimuthal coverage was chosen to represent that of a long-period North American super-network of 55 stations used for the actual NTS events. We compared these errors in moment estimate to those obtained from surface wave magnitude (M sub s) and spectral scalar moment (M sub 0) measurements for the same surface wave observations. For a ratio of M sub expl/M sub eq less than 1.0 we found that the inverted M sub I solution is a much better estimate of the actual isotropic moment than either M sub s or M sub O, and the standard deviation in this estimate is substantially less than that using the other two methods for the great majority of isotropic source + double couple sources. Even when the inversion constraints are off in dip and rake each by 30 deg, the mis-estimate of the isotropic moment is less than 35 percent of the actual value.

Descriptors :   *SEISMIC DETECTION, *ARMS CONTROL, *NUCLEAR EXPLOSION DETECTION, *SEISMIC DISCRIMINATION, YIELD(NUCLEAR EXPLOSIONS), SYMPOSIA, SURFACE WAVES, VERIFICATION, UNDERGROUND EXPLOSIONS, MOMENTS, STRAIN(MECHANICS), NUCLEAR EXPLOSION TESTING, FAULTS(GEOLOGY), ANISOTROPY, LEAST SQUARES METHOD, SEISMIC WAVES, TREATIES, AZIMUTH, RAYLEIGH WAVES, TECTONICS, LOVE WAVES.

Subject Categories : Government and Political Science
      Seismology
      Seismic Detection and Detectors
      Nuclear Weapons

Distribution Statement : APPROVED FOR PUBLIC RELEASE