HR: 15:25h
AN: S43D-08    [Abstracts]
TI: Examination of the Predictive Waiting Time Method Using Global Earthquake Catalogs
AU: * Gu, Y J
EM: jgu@phys.ualberta.ca
AF: University of Alberta, Department of Physics, University of Alberta 535A Avadh Bhatia Phyisics Lab, Edmonton, AB T6G2J1 Canada
AU: Chong, L
EM: lychong@ualberta.ca
AF: University of Alberta, Department of Physics, University of Alberta 535A Avadh Bhatia Phyisics Lab, Edmonton, AB T6G2J1 Canada
AU: Gu, J
EM:
AF: High-Tech O&E Corp, 620 Mass Ave, Cambridge, MA 02139 United States
AB: The Gutenberg-Richter magnitude frequency relationship offers a single process triggering model to build statistical models of seismicity. And by using these statistical models, one can potentially predict the likelihood of aftershocks within a predetermined level of uncertainty. While this simple relationship is shown to be important as a statistical measure of the number of aftershocks, it is not effective in describing the occurrence time (to within some margin of error) of a given aftershock, particularly large aftershocks that could be important for seismic hazard mitigation. In this paper we examine the effectiveness of an alternative large-aftershock predictive method, the Waiting Time Method (WTM, first proposed by Li and Gu, 1979), using the NEIC catalog. The relationship can be written as log(dT)=Alog(T)+B, where A and B are constants, T is the time of the large aftershocks and dT is the elapsed time of the aftershock in discussion from the previous one. This relationship explicitly explores a simple linear relationship (in log-log domain) between the occurrence of an event and its association with the previous event; A and B can be determined numerically in real time. We examined all of the magnitude 7 -8+ (M) events in the NEIC catalog. We select different aftershock zone radii and aftershock cutoff periods after the main event based on the aftershock magnitude. Our results show WTM explains the occurrences of large aftershocks for nearly 90% of the events above 7.6. The averaged slopes are 0.7-0.9 with uncertainties less than 0.1. WTM explains ~70% of the large aftershocks of mainshocks with magnitudes less than 7.6. Considering the lower aftershock magnitude threshold (M5 or less) for M7 mainshocks, the slightly worse (but still statistically significant) performance may result from magnitude uncertainties. Our results strongly suggest that WTM is a robust empirical relationship for describing large aftershocks and may have important applications in earthquake prediction and classification. Among the parameters that could be improved for further considerations are the lower threshold values for the definition of aftershocks. The lowest magnitude values depend on the type of the fault and the mainshock location. We find that empirical values of 2-3 yield optimal results. Efforts are being made to develop an automated classification algorithm based on WTM and to quantify the regional variation of A and B values.
DE: 7200 SEISMOLOGY
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
SC: Seismology [S]
MN: Fall Meeting 2005