Regional Seismic Event Discrimination In Siberia
Abstract
In July and August of 1987, three Peaceful Nuclear Explosions (PNEs) were detonated in the northern Baikal Rift. These PNEs, each near m(b) 5.0, were recorded at teleseismic distances and are listed in global seismic bulletins. Broadband and short-period sensors were being digitized at Chinese Digital Seismic Network (CDSN) station HIA during that summer (at event-station distances of about 1450 km). As HIA will become an International Monitoring System (IMS) primary array, these PNEs provide an excellent opportunity to test and calibrate regional, short-period discriminants in preparation for future test-ban monitoring. Hence, we retrieved HIA records of the explosions from the IRIS Data Management Center (DMC) along with about 400 additional presumed earthquakes from central Siberia, eastern Mongolia, and northeastern China. Binning event origin times into time-of-day histograms indicates uniform event distribution throughout the 24-hour day. We therefore concluded that the event catalogs (PDE and REB) used for data retrieval were not contaminated with industrial explosions. We tested short-period discriminants by measuring root-mean-square (RMS) amplitudes of P(n), P(g), S(n), and L(g) phases and then formed amplitude ratios using several frequency band measurements between 1 and 6 Hz. For most events, event-station distances are between 400 and 1600 km from KIA, with P(n) being the first arrival. P(g) and S(n) are generally difficult to identify as distinct arrivals. L(g) is the strongest secondary arrival. After correcting ratios for distance effect, the P(n)/L(g) ratios at frequencies above 3 Hz separate the explosions from the earthquakes. The P(n)/L(g) cross-spectral ratios (P(n) above 3 Hz and L(g) near 1 Hz) also separate the explosions from the earthquakes.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2000
- Accession Number
- ADA530000
Entities
People
- Hans E. Hartse
Organizations
- Los Alamos National Laboratory