2-D Path Corrections for Local and Regional Coda Waves: A Test of Transportability

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Reliable estimates of the seismic source spectrum are necessary for accurate magnitude, yield, and energy estimation. In particular, how seismic radiated energy scales with increasing earthquake size has been the focus of recent debate within the community and has direct implications on earthquake source physics studies as well as hazard mitigation. The 1-D coda methodology of Mayeda et al. [2003] has provided the lowest variance estimate of the source spectrum when compared against traditional approaches that use direct S-waves, thus making it ideal for networks that have sparse station distribution. The 1-D coda methodology has been mostly confined to regions ... continued below

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Mayeda, K M; Malagnini, L; Phillips, W S; Walter, W R; Dreger, D S & Morasca, P July 13, 2005.

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Reliable estimates of the seismic source spectrum are necessary for accurate magnitude, yield, and energy estimation. In particular, how seismic radiated energy scales with increasing earthquake size has been the focus of recent debate within the community and has direct implications on earthquake source physics studies as well as hazard mitigation. The 1-D coda methodology of Mayeda et al. [2003] has provided the lowest variance estimate of the source spectrum when compared against traditional approaches that use direct S-waves, thus making it ideal for networks that have sparse station distribution. The 1-D coda methodology has been mostly confined to regions of approximately uniform complexity. For larger, more geophysically complicated regions, 2-D path corrections may be required. We will compare performance of 1-D versus 2-D path corrections in a variety of regions. First, the complicated tectonics of the northern California region coupled with high quality broadband seismic data provides for an ideal ''apples-to-apples'' test of 1-D and 2-D path assumptions on direct waves and their coda. Next, we will compare results for the Italian Alps using high frequency data from the University of Genoa. For Northern California, we used the same station and event distribution and compared 1-D and 2-D path corrections and observed the following results: (1) 1-D coda results reduced the amplitude variance relative to direct S-waves by roughly a factor of 8 (800%); (2) Applying a 2-D correction to the coda resulted in up to 40% variance reduction from the 1-D coda results; (3) 2-D direct S-wave results, though better than 1-D direct waves, were significantly worse than the 1-D coda. We found that coda-based moment-rate source spectra derived from the 2-D approach were essentially identical to those from the 1-D approach for frequencies less than {approx}0.7-Hz, however for the high frequencies (0.7 {le} f {le} 8.0-Hz), the 2-D approach resulted in inter-station scatter that was generally 10-30% smaller. For complex regions where data are plentiful, a 2-D approach can significantly improve upon the simple 1-D assumption. In regions where only 1-D coda correction is available it is still preferable over 2-D direct wave-based measures.

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PDF-file: 12 pages; size: 1.3 Mbytes

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  • Presented at: Seismic Research Review, Palm Springs, CA, United States, Sep 20 - Sep 22, 2005

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  • Report No.: UCRL-PROC-213608
  • Grant Number: W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 881646
  • Archival Resource Key: ark:/67531/metadc876790

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  • July 13, 2005

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  • Sept. 21, 2016, 2:29 a.m.

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  • Nov. 22, 2016, 1:35 p.m.

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Mayeda, K M; Malagnini, L; Phillips, W S; Walter, W R; Dreger, D S & Morasca, P. 2-D Path Corrections for Local and Regional Coda Waves: A Test of Transportability, article, July 13, 2005; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc876790/: accessed August 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.