TitleMoment-magnitude relations in theory and practice
AuthorsThomas C. Hanks; David M. Boore
JournalJournal of Geophysical Research

The observation that motivates this study is the difference in c values in moment-magnitude relations of the form log M0 = cML + d between central and southern California. This difference is not at all related to geographical area; rather, it results from positive curvature in the log M0 - ML plane and the relatively large number of ML < 5 earthquakes in the central California data set. With the prescription that the far-field shear waves from which ML is taken be finite-duration, band-limited, white Gaussian noise in acceleration, we can estimate ML as a function of M0 alone, by fixing the arms stress drop at 100 bars and fmax at 15 Hz. These model calculations fit available California moment-magnitude data for 0 ≲ ML ≲ 7, 1017 ≲ M0 ≲ 1028 dyne cm with striking accuracy. This range in source strength is entire: earthquakes with M0 ≥ 1028 dyne cm are unlikely to occur in California, and earthquakes with ML < 0 cannot be recorded in California, at least under ordinary conditions of recording earthquakes at ordinary hypocentral depths. More fundamentally, the remarkably good fit of model to data implies that the arms stress drop of 100 bars (to a factor of 2 or so) is a stable and pervasive feature of all (ML ≳ 2 1/2) California earthquakes whose spectral corner frequency lies in the "visible" bandwidth, f0 ≤ fmax.

NoFileURLAccess Date
1.PDF Document (570.65 KB)
Created: Serkan GIRGIN, 2013/01/28 16:49:13

Risk Assessment

Natural Hazards

Industrial Plants