HR: 1340h
AN: S43A-1039    [Abstracts]
TI: Re-analysis of the largest 24 instrumentally recorded earthquakes since the beginning of the 20th Century
AU: * Villasenor, A
EM: antonio@ija.csic.es
AF: Institute of Earth Sciences "Jaume Almera", Lluis Sole i Sabaris s/n, Barcelona, 08028, Spain
AU: Benz, H M
EM: benz@usgs.gov
AF: U.S. Geological Survey, Box 25046, MS 966 Denver Federal Center, Denver, CO 80225, United States
AU: Engdahl, E R
EM: engdahl@iaspei.org
AF: University of Colorado, Campus Box 390, Boulder, CO 80309, United States
AB: We have revised the size estimates, nucleation points, rupture areas and aftershock distributions of all the instrumentally recorded earthquakes with a seismic moment greater than or equal to 3.0E+28 dyne-cm, equivalent to a moment magnitude of 8.25. Re-analysis of these events was done in order for the United States Geological Survey (USGS) to publish a new series of global seismic maps based on the global seismicity compilation of Villasenor and Engdahl (2002). In addition, the USGS is using this information to provide better historical content and calibration information in its rapid response applications. We have compiled from the literature seismic moment estimates for all potential earthquakes with Mw greater or equal than 8.25, and we have selected a preferred value based on objective criteria. This has resulted in a total of 24 M8.25 or greater earthquakes in the time period 1905-2006. For these earthquakes we have then compiled focal mechanisms obtained using waveform modeling/inversion methods or inferred the mechanism from recent larger earthquakes that occurred in the vicinity of the event. We have relocated all the main shocks and aftershocks for which phase arrival time data are available from the ISS (International Seismological Summary) or ISC (International Seismological Centre). Relocation of the main event provides an estimate of the nucleation point, while the aftershock distribution is used to delineate the rupture zone. For earthquakes in the early part of the 20th century, rupture zones are also constrained by macroseismic data and surface effects (uplift or surface rupture). For more recent earthquakes we have constrained rupture estimates from finite-fault slip modeling. The 24 largest earthquakes analyzed in this study are all shallow-depth earthquakes. Nineteen of these earthquakes are best described as megathrust subduction events, 2 are outer-rise normal faulting events, 2 are intra-slab ruptures, and 1 is an intraplate strike-slip earthquake.
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7240 Subduction zones (1207, 1219, 1240)
SC: Seismology [S]
MN: 2007 Fall Meeting