Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by COHEN, T. J. Search for Related Content GeoRef GeoRef Citation

Coda suppression capabilities of the beam and mixed-signal processor

ALEXANDRIA LABORATORIES TELEDYNE GEOTECH, ALEXANDRIA, VIRGINIA

Abstract

Using data recorded on 7- and 19-element subarrays at TFO, we compare the relative abilities of the beam and a mixed-signal processor to attenuate P-wave codas. The P-wave signals from various earthquakes are time-shifted to simulate arrivals from different azimuths and 60° distance. These signals are assumed to mask an explosion detonated at Semipalatinsk, about 96° distant from TFO. The analysis consists of determining how much of signal 1 (the earthquake) leaks into our estimate of signal 2 (the event being masked). Because the beam and mixed-signal processor are linear processors, signal 2 need not actually be present; we need only determine how much of signal 1 is present in our estimate of signal 2. The coda attenuation capability of the mixed-signal processor is found to exceed that of the beam. Up to 14-db improvement over the beam is obtained, although improvement is generally on the order of 3 to 5 db for both subarrays. A nominal value of 18 db is representative of the maximum coda attenuation obtained using the mixed-signal processor and the 19-element subarray; for the 7-element subarray, maximum attenuation is roughly 14 db. Coda attenuation obtained using the 7-element subarray and the mixed-signal processor is comparable to that obtained using the 19-element subarray and the beam. Preliminary results suggest that when the difference in the ray parameter vectors is small, a large-aperture array and the mixed-signal processor are required for significant (9 db) coda attenuation.