Global variations of stress drop for moderate to large earthquakes

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  • Bettina P. Allmann
    Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography University of California, San Diego La Jolla California USA
  • Peter M. Shearer
    Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography University of California, San Diego La Jolla California USA

書誌事項

公開日
2009-01
権利情報
  • http://onlinelibrary.wiley.com/termsAndConditions#vor
DOI
  • 10.1029/2008jb005821
公開者
American Geophysical Union (AGU)

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説明

<jats:p>We investigate the global variation of earthquake stress drops using spectra of about 2000 events of <jats:italic>m</jats:italic><jats:sub><jats:italic>b</jats:italic></jats:sub> ≥ 5.5 between 1990 and 2007. We use an iterative least squares method to isolate source displacement spectra from travel path and receiver contributions, based on a convolutional model. The observed <jats:italic>P</jats:italic> wave source spectra are corrected with a globally averaged empirical correction spectrum and estimates of near‐source attenuation. Assuming a Brune‐type source model, we estimate corner frequencies and compute stress drops. Stress drop estimates for individual earthquakes range from about 0.3 to 50 MPa, but the median stress drop of about 4 MPa does not vary with moment, implying earthquake self‐similarity over the <jats:italic>M</jats:italic><jats:sub><jats:italic>w</jats:italic></jats:sub> = 5.2 to 8.3 range of our data. A comparison of our results with previous studies confirms this observation over most of the instrumentally observable magnitude range. While the absolute values of our estimated stress drops depend upon the assumed source model, we identify relative regional variations of stress drop that are robust with respect to the processing parameters and modeling assumptions, which includes an inherent assumption of constant rupture velocity. We find a dependence of median stress drop on focal mechanism, with a factor of 3–5 times higher stress drops for strike‐slip earthquakes and also find a factor of 2 times higher stress drops for intraplate earthquakes compared to interplate earthquakes.</jats:p>

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