Modeling the difference in ground-motion magnitude-scaling in small and large earthquakes

Douglas, John and Jousset, Philippe (2011) Modeling the difference in ground-motion magnitude-scaling in small and large earthquakes. Seismological Research Letters, 82 (4). pp. 504-508. ISSN 1938-2057

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Abstract

It is often the case that ground-motion records for a given area of interest are available in relative abundance for small (Mw < 5) earthquakes but are practically non-existent for larger earthquakes, which have the potential to cause damage to structures. This is a direct consequence of the almost universally observed Gutenberg-Richter relation that a unit increase in magnitude decreases the number of earthquakes observed by a factor of ten (e.g., Frohlich and Davis 1993, Douglas 2003). The productive use of data from small earthquakes for seismic hazard assessments relies on knowledge of how earthquake ground motions scale with magnitude. The majority of ground-motion prediction equations (GMPEs) are derived, usually by regression analysis, to estimate shaking from earthquakes with Mw ≳ 5 (Douglas 2011), but there is often little consideration given to how they extrapolate to small magnitudes, which are sometimes considered within the hazard integral of probabilistic seismic hazard assessments or for the testing of GMPEs against observations, especially for regions of low-to-moderate seismicity.