Regional Body-Wave Discrimination Research
Abstract
Monitoring the world for potential nuclear explosions requires identifying them by their expected seismic signatures and discriminating them from earthquakes and other sources of seismic waves. Large events (approximately m(b) greater than 4.0) can often be successfully identified by the MS:mb discriminant. In order to monitor small events (approximately m(b) less than 4.0) short-period regional waveform data recorded within 2000 km will be needed because of poor signal-to-noise at large distances and/or long-periods. Many studies have shown that short-period (0.5-10 Hz) regional body wave phases (e.g. Pn, Pg, Sn, Lg and coda) have excellent discrimination power down to very small magnitudes when used at various nuclear tests sites. In order to broaden the application of these regional body wave techniques, we are developing size-, distance- and location-based corrections to apply to the regional data to allow wider data comparison and better discrimination performance. Building on prior work (e.g. Taylor et al. 1999, Rodgers and Walter, 2000), we are developing a revised Magnitude and Distance Amplitude Correction (MDAC) procedure. The procedure makes use of the very stable moment magnitude determinations from regional coda envelopes (see Mayeda et al, this Symposium) to provide an independent size estimate. Using a Brune (1970) style omega-squared source spectral model, we parameterize the source in terms of apparent stress and its scaling with moment. For the distance corrections we parameterize in terms of geometrical spreading, and frequency-dependent attenuation. In addition there are constants associated with velocities, densities and a phase- and frequency-dependent site effect. Using this relatively simple model we can remove much of the magnitude and distance trends from the regional data.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2000
- Accession Number
- ADA529916
Entities
People
- Arthur Rodgers
- Kevin Mayeda
- Steve Taylor
- William R. Walter
Organizations
- Lawrence Livermore National Laboratory