Global evaluation of large earthquake energy from 1997 through mid-2010

Abstract

We develop an updated radiated seismic energy E catalog of global earthquakes with seismic moment M0 1019 Nm (MW 6.7) from 1997 through mid-2010, recording 342 events using 17849 seismograms. Station-specific corrections and event duration-dependent total P wave group calculations allow for improved E determinations for large-and long-duration earthquakes. We find the global mean energy-to-moment ratio ${\bar \theta}$ = log10 (E/M0) =-4.59 0.36. Robust deviations are found for thrust (${\bar \theta}$T =-4.74), strike-slip (${\bar \theta}$SS =-4.44), and normal (${\bar \theta}$N =-4.51) faulting events. For two regions with recent energy deficient tsunami earthquakes (TsE), we examine all large thrust earthquakes with M0 5 × 1017 Nm (MW 5.7), to identify a regional characterization in their relative radiated energy-to-moment ratio. While thrust events along Java, Indonesia, the site of two TsE events in 1994 and 2006, are comparable (${\bar \theta}$T-JV =-4.91) to the global thrust average, events along the Middle America Trench (MAT), the site of the 1992 Nicaragua TsE, are consistently deficient (${\bar \theta}$T-MAT =-5.15). Along the MAT, a trend of increased deficiency in radiated energy to the southeast occurs in the direction of more rapid plate convergence. Global thrust mechanisms become increasingly deficient in radiated seismic energy at shallow depths, with TsE events representing the shallowest and most energetically deficient end-member of the events in the study. Results suggest thrust events are highly variable but tend to increase in apparent stress from about 15 kPa near the surface to 2 MPa near 70 km depth. Copyright 2011 by the American Geophysical Union.