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DTIC ADA337234: Improved Methods for Regionalized Surface Wave Anal... |
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by Defense Technical Information Center |
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We develop optimized methods for measuring surface waves |
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for event screening under a CTBT. The optimization |
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techniques are: a regionalized earth model, phase-matched |
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filtering, path corrected surface wave spectral |
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magnitude; maximum likelihood magnitudes and upper |
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bounds. A regionalized earth model is developed by |
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tomographic inversion of surface wave data starting with |
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the Crust 5.1 earth models, and using dispersion |
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measurements from PIDC data, historic explosion data, and |
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data sets from the University of Colorado, Harvard, and |
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St. Louis University. Dispersion curves derived from the |
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final earth models are sufficient to predict dispersion |
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and to generate phase-matched filters for most regions of |
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the world. The detection threshold of the automatic |
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surface wave processor at the PIDC is found to be one |
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magnitude unit lower than NEIC bulletins. Maximum |
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likelihood magnitudes are calculated for a data set of |
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700 events using 10,000 PIDC and historical explosion |
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seismograms. Maximum likelihood magnitudes combined with |
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maximum likelihood upper bounds allow discrimination to |
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about mb 4.0. The Ms:mb discrimination line between |
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earthquakes and explosions has a slope of 1.4. We |
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recommend redefining Ms as Ms = log A/T+k logdelta+1/2 |
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log(sindelta)+gammadeltalog e+D using the parameters |
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found by Rezapour and Pearce (1997), and recommend using |
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path corrected spectral magnitudes as an alternative to |
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Ms. |
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Date Published: 2018-04-11 08:40:07 |
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Identifier: DTIC_ADA337234 |
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Item Size: 110026156 |
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Language: english |
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Media Type: texts |
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# Topics |
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DTIC Archive; Stevens, J. L.; MAXWELL... |
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dticarchive |
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# Uploaded by |
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@chris85 |
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