Interactive and Automatic Modes of Long-Period Signal Extraction Using Cascaded Filters
ENSCO INC ALEXANDRIA VA SEISMIC APPLIED RESEARCH DIV
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The purpose of this work was to develop and evaluate an interactive long-period signal extraction filter suite. Five filters were included in the suite and were applied to test data in a cascaded mode, i.e., the output of one filter served as the input to the next filter. The filters tested were a bandpass filter, a Wiener filter, a chirp matched filter, a polarization filter, and a Gaussian narrowband filter. It was found that, for the filters examined, the polarization filter dominates the cascaded filtering approach to signal extraction specifically, processing gains as high as 14 to 15 dB were realized from the application of cascaded filters which included this filter. Further, tests performed on a Eurasian data set using one specific cascaded filter sequence yielded an improvement in surface wave detection capability equivalent to an improvement in bodywave detectability of approximately 0.6 to 0.8 m sub b units. Finally, cascaded filters were found to provide more detected signals from which surface wave magnitudes can be obtained as such, the use of these filters can enhance an analysts capability to discriminate between earthquakes and explosions.
- Seismic Detection and Detectors