Investigation of Upper Mantle Structure in Central Eurasia from Analysis of Broad-Band Far Regional Seismograms (and Comparison to Western U.S.).
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)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1994
- Accession Number
- ADA295670
Entities
People
- Karl Koch
Organizations
- Southern Methodist University