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

Abstract

[1] We develop an updated radiated seismic energy E catalog of global earthquakes with seismic moment M 0 ≥ 10 19 Nm (M W ≥ 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 = log 10 (E/M 0 ) = −4.59 ± 0.36. Robust deviations are found for thrust ( T = −4.74), strike-slip ( SS = −4.44), and normal ( N = −4.51) faulting events. For two regions with recent energy deficient tsunami earthquakes (TsE), we examine all large thrust earthquakes with M 0 ≥ 5 × 10 17 Nm (M W ≥ 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 ( 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 ( 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.

New perspectives on self‐similarity for shallow thrust earthquakes

“…We use the CRUST1.0 velocity model to account for the ratio ∕ to be consistent throughout our study. However, it should be noted that some observations have found that P corner frequencies are higher than S corner frequencies and estimates of q have ranged from 9 to 25 [Boatwright and Fletcher, 1984;Prieto et al, 2004], although often assumed constant in large data set studies [Convers and Newman, 2011].…”

“…Boatwright [1980] directly measured the radiated energy flux by preserving the amplitude information in the waveforms, which, when integrated over enough stations (azimuth and takeoff angles), is a direct measure of radiated energy. In all studies that measure energy with this approach [Convers and Newman, 2011;Pérez-Campos and Beroza, 2001], the path effects are removed using a simplified Earth Green's function with attenuation and geometrical spreading. However, because absolute amplitude calibration can be difficult to perform accurately, a second approach normalizes the seismogram (i.e., to the zero-frequency asymptote of its spectrum), assumes a consistent spectral shape over all azimuths and takeoff angles, and often uses an independent measure of seismic moment to calibrate the long-period spectral level.…”

Rapidly Estimated Seismic Source Parameters for the 16 September 2015 Illapel, Chile M w 8.3 Earthquake

“…The broadband energy estimate posted by IRIS is 3.2 9 10 16 J (http://ds. iris.edu/spud/eqenergy/10095476) based on the method of CONVERS and NEWMAN (2011).…”

Analysis of seismic magnitude differentials (m b−M w) across megathrust faults in the vicinity of recent great earthquakes

“…Weak trends may be present for the Sumba and the sparsely sampled Peru source regions, but no clear trend is apparent for the wellsampled Kuril and Aleutian arcs and linear regressions did not give significant slope estimates. Maps of data distributions indicate that localized areas along subregions such as Java (also see Bilek and Engdahl, 2007;Convers and Newman, 2011) or Kamchatka may have depth-dependent trends, but the along-arc averaging obscures this as there is large scatter in the data. Since the localized regions tend to have fewer data, we will defer further analysis of other regions to future detailed studies that improve the depth estimates and more fully characterize the source spectra of events on the megathrust.…”