Physical links between crustal deformation, seismic moment and seismic hazard for regions of varying seismicity

Abstract

Seismic moment release rates M0 inferred from a Weibull frequency‐magnitude distribution and its extreme value equivalent are compared with observation. The seismotectonically diverse regions studied all exhibit the curvature of a log‐linear frequency magnitude plot associated with applying a maximum magnitude to earthquake recurrence statistics. The inferred seismic moment release rates are consistent with available crustal deformation data within uncertainties resulting from the line fit and in magnitude determination. The uncertainties for the regions studied (Southern California, the New Madrid seismic zone, the Central and Eastern Mediterranean and mainland UK) vary from at worst an order of magnitude down to a factor of 2 or 3. This agreement can be used to justify the extrapolation of frequency‐magnitude statistics beyond the historical and instrumental era in seismic hazard studies as a test of the stationarity of short‐term statistics against long‐term effects. A striking example of a bimodal seismicity distribution is observed in the New Madrid zone. This can be interpreted as being due to the superposition of two distinct seismogenic source types observed in the area. A quantitative analysis of the separate orders of seismicity observed in the frequency‐magnitude statistics ‐ comparing the different maximum magnitudes and inferred seismic moment release rates with those observed ‐ supports this hypothesis. Superposition of many such seismogenic sources can explain the linearity observed in global frequency versus seismic moment magnitude statistics. Copyright © 1984, Wiley Blackwell. All rights reserved