Accession Number : ADA295670

Title :   Investigation of Upper Mantle Structure in Central Eurasia from Analysis of Broad-Band Far Regional Seismograms (and Comparison to Western U.S.).

Descriptive Note : Final rept. 15 Jul 91-30 Jul 94,

Corporate Author : SOUTHERN METHODIST UNIV DALLAS TX

Personal Author(s) : Koch, Karl

PDF Url : ADA295670

Report Date : JUL 1994

Pagination or Media Count : 44

Abstract : Waveforms from nuclear explosions at the B. Kazakhistan test site were recorded at ARU & GAR at the distance range studied for Nevada Test Site explosions(between 1380 and 1540 km). Waveforms at ARU are characterized by weak initial P waves following by strong secondary arrivals within 5 seconds. Within approximately 14 seconds comes a strong later arrival, preceded by a longer-period arrival. Filtering in different frequency bands shows initial P wave & long period arrival are consistent with an amplitude ratio of 1:2. Other arrivals are high-frequency & vanish for periods longer than 2 sec. Synthetic reflectivity seismogram calculations test previous P wave models for Central Eurasia for compatibility with identified waveform patterns. Most models produce impulsive 1st arrivals & fail to generate strong secondary arrivals. Only models by Mechie et al. (1993) & Priestley & Cipar (1994) show some observed P wave patterns. With a new model strong secondary arrivals are generated with observed frequencies & attribute these arrivals to a Moho underside reflection & free surface reflection PP. (MM)

Descriptors :   *SEISMIC DETECTION, *SEISMIC WAVES, *NUCLEAR EXPLOSION DETECTION, *EARTH MANTLE, *SEISMOGRAPHS, NUCLEAR EXPLOSIONS, WAVEFORMS, SEISMIC DATA, SEISMIC REFLECTION, FREQUENCY BANDS, BROADBAND, EARTH CRUST, RANGE(DISTANCE), SEISMIC VELOCITY, TEST FACILITIES, EURASIA, STRUCTURAL GEOLOGY, PRIMARY WAVES(SEISMIC WAVES), POISSON RATIO, TECTONICS, SECONDARY WAVES, MOHOROVICIC DISCONTINUITY.

Subject Categories : Seismology
      Seismic Detection and Detectors
      Nuclear Weapons

Distribution Statement : APPROVED FOR PUBLIC RELEASE