HR: 08:00h
AN: S51C-01    [Abstracts]
TI: An Extension to Short Distances of Real-Time Estimators of Seismic Sources
AU: * Ebeling, C W
EM: carl@earth.northwestern.edu
AF: Northwestern University Department of Earth and Planetary Sciences, 1850 Campus Drive, Evanston, IL 60208, United States
AU: Okal, E A
EM: emile@earth.northwestern.edu
AF: Northwestern University Department of Earth and Planetary Sciences, 1850 Campus Drive, Evanston, IL 60208, United States
AB: Working from a data set of seismograms from 61 large events recorded at epicentral distances between 5 and 35 degrees, we assess the validity at short distances of the teleseismic (35 to 80 deg.) method of Newman and Okal (1998) using the ratio of estimated energy to moment (theta) to characterize a seismic source in real time. An evaluation of short-distance data from 17 events common to this study and that of Newman and Okal shows good agreement in calculated theta values. Deficient values of theta in this study are observed for the December 2004 N. Sumatra (theta -6.82), June 1994 S. of Java (-6.70), September 1992 Nicaragua (-6.44), July 2006 S. of Java (-6.04), and November 2006 Kuril Island (-6.00) events; all of these have been previously recognized as having unusual sources. Other notable events with slightly less-deficient theta values are June 2001 Peru (-5.81) and February 1996 Peru (-5.67). For this data set we also present an extension of the discriminant tau method of Reymond et al. (AGU, 2006) based on evaluation of the envelope of 2-4 Hz bandpass filtered P arrival windows. Preliminary results show that both theta and tau discriminants may be used to improve real-time identification of seismic sources with the potential to generate anomalously large tsunamis.
DE: 7203 Body waves
DE: 7215 Earthquake source observations (1240)
SC: Seismology [S]
MN: 2007 Fall Meeting