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Title: Improving mb:Ms discrimination using phase matched filters derived from regional group velocity tomography

Abstract

This study reports on the ongoing investigation of surface wave group velocity dispersion across the Middle East and North Africa. Using broadband data gathered from various sources, we have measured group velocity using a multiple narrow-band filter method. To date, we have examined over 13,500 seismograms and made quality measurements for about 6500 Rayleigh and 3500 Love wave paths. A conjugate gradient method is used to perform the group velocity tomography at several periods. There is excellent agreement between short period structure and large known sedimentary features. Longer period structure is sensitive to crustal thickness, particularly the contrast between continental and oceanic regions and thicker crusts found beneath erogenic zones. We also find slow upper mantle velocities along rift systems. Correlation between the inversion results and known major tectonic features gives us confidence in our surface wave group velocities. Accurate group velocity maps can be used to construct phase matched filters. The filters can improve weak surface waves by compressing the dispersed signal. We are particularly interested in using the filters to calculate regionally determined M{sub s} measurements, which we hope can be used to extend the threshold of m{sub b}:M{sub s} discriminants to lower magnitude levels. A preliminary analysismore » of surface wave data processed using phase matched filters indicates a significant improvement in increasing the signal-to-noise ratio and improving magnitude estimates. Where signal-to-noise is very poor, phase matched filtering can still be useful in lowering the upper bound on M{sub s} measurements. We propose a series of tests in order to analyze the utility of phase matched filters. Goals of the study include determining at what distance and magnitude ranges we can expect to see improvement using the filters and the overall effect of the filters on discrimination capability. We also propose to look at seismic velocity models of the Middle East and North Africa region in order to test the discrimination performance achieved using the various models.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE Office of Defense Programs (DP) (US)
OSTI Identifier:
14600
Report Number(s):
UCRL-JC-134305; GC0402000
GC0402000; TRN: AH200129%%331
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: 21st Seismic Research Symposium: Technologies for Monitoring the Comprehensive Nuclear Test Ban Treaty, Las Vegas, NV (US), 09/21/1999--09/24/1999; Other Information: PBD: 23 Jul 1999
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; AFRICA; MIDDLE EAST; MONITORING; PERFORMANCE; SEISMIC SURFACE WAVES; SIGNAL-TO-NOISE RATIO; TECTONICS; THICKNESS; TOMOGRAPHY; VELOCITY

Citation Formats

Ford, S R, Hazler, S, Pasyanos, M E, and Walter, W R. Improving mb:Ms discrimination using phase matched filters derived from regional group velocity tomography. United States: N. p., 1999. Web.
Ford, S R, Hazler, S, Pasyanos, M E, & Walter, W R. Improving mb:Ms discrimination using phase matched filters derived from regional group velocity tomography. United States.
Ford, S R, Hazler, S, Pasyanos, M E, and Walter, W R. 1999. "Improving mb:Ms discrimination using phase matched filters derived from regional group velocity tomography". United States. https://www.osti.gov/servlets/purl/14600.
@article{osti_14600,
title = {Improving mb:Ms discrimination using phase matched filters derived from regional group velocity tomography},
author = {Ford, S R and Hazler, S and Pasyanos, M E and Walter, W R},
abstractNote = {This study reports on the ongoing investigation of surface wave group velocity dispersion across the Middle East and North Africa. Using broadband data gathered from various sources, we have measured group velocity using a multiple narrow-band filter method. To date, we have examined over 13,500 seismograms and made quality measurements for about 6500 Rayleigh and 3500 Love wave paths. A conjugate gradient method is used to perform the group velocity tomography at several periods. There is excellent agreement between short period structure and large known sedimentary features. Longer period structure is sensitive to crustal thickness, particularly the contrast between continental and oceanic regions and thicker crusts found beneath erogenic zones. We also find slow upper mantle velocities along rift systems. Correlation between the inversion results and known major tectonic features gives us confidence in our surface wave group velocities. Accurate group velocity maps can be used to construct phase matched filters. The filters can improve weak surface waves by compressing the dispersed signal. We are particularly interested in using the filters to calculate regionally determined M{sub s} measurements, which we hope can be used to extend the threshold of m{sub b}:M{sub s} discriminants to lower magnitude levels. A preliminary analysis of surface wave data processed using phase matched filters indicates a significant improvement in increasing the signal-to-noise ratio and improving magnitude estimates. Where signal-to-noise is very poor, phase matched filtering can still be useful in lowering the upper bound on M{sub s} measurements. We propose a series of tests in order to analyze the utility of phase matched filters. Goals of the study include determining at what distance and magnitude ranges we can expect to see improvement using the filters and the overall effect of the filters on discrimination capability. We also propose to look at seismic velocity models of the Middle East and North Africa region in order to test the discrimination performance achieved using the various models.},
doi = {},
url = {https://www.osti.gov/biblio/14600}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1999},
month = {7}
}

Conference:
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