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Depth variation of coseismic stress drop explains bimodal earthquake magnitude‐frequency distribution
Author(s) -
Zielke O.,
Arrowsmith J. R.
Publication year - 2008
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2008gl036249
Subject(s) - magnitude (astronomy) , geology , earthquake magnitude , seismology , induced seismicity , seismic hazard , power law , geodesy , geometry , scaling , physics , statistics , mathematics , astronomy
An essential part of seismic hazard analysis is the earthquake size‐frequency relationship, used to estimate earthquake recurrence time, and thus probability. A key feature of those distributions is their bimodal character: small to moderate magnitude earthquakes follow the Gutenberg‐Richter (GR) inverse power‐law relation while large magnitude (characteristic) earthquakes are more frequent than anticipated from GR, following approximately a gaussian distribution around the maximum magnitude limited by fault geometry. Using a numerical earthquake simulator, we show that the temperature dependence of friction behavior and therefore the depth‐variation of coseismic stress drop, derived from laboratory friction experiments, presents a simple and comprehensive explanation for the observed bimodal seismicity distribution. Characteristic earthquakes are the result of an abrupt increase in rupture width at the transition from small to large earthquakes.