HR: 0800h
AN: S11C-0712    [Abstracts]
TI: Is Gutenberg-Richter b value uniform in California and are spontaneous earthquakes stationary in California?
AU: * Wang, Q
EM: qiwang@ucla.edu
AF: UCLA Department of Earth and Space Sciences, 595 Young Drive East, Los Angeles, CA 90095, United States
AU: Jackson, D
EM: djackson@ucla.edu
AF: UCLA Department of Earth and Space Sciences, 595 Young Drive East, Los Angeles, CA 90095, United States
AU: Zhuang, J
EM: zhuangjc@ism.ac.jp
AF: The Institute of Statistical Mathematics, 4-6-7 Minamiazabu, Minato-ku, Tokyo, 106-8569, Japan
AB: The b value in Gutenberg-Richer relationship is very important in seismology because it is critical for both hazard analysis and physical understanding of earthquakes: the small change of the b value can lead a large change in the predicted number of large earthquakes. It is very important and interesting to explore where the b value in California in uniform or not. The maximum likelihood method of Aki (1965) is the most accurate way to calculate b value, but the uncertainty of b value due to the uncertainty of magnitude, the earthquake catalog incompleteness and the magnitude round off errors is hard to calculate. Different regions may have different b value and different uncertainties of b value. We divide California into several regions, calculate possible both a and b value with 95% confidence in different regions using simulated catalogs after adding all kinds of errors and finally test whether the b value in California is uniform or not. There are two types of earthquakes: spontaneous and triggered. The separation of these two types of earthquakes, called declustering, helps us to understand more about both kinds and their relationships. Because spontaneous seismicity responds local plate movement and stress accumulation, it is useful and helpful to study whether spontaneous seismicity in California is stationary or not. We use ETAS model to decluster the catalog and find that the spontaneous seismicity is stationary in southern California after 1940 while it is not stationary in northern California after 1940.
DE: 7200 SEISMOLOGY
DE: 7215 Earthquake source observations (1240)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7290 Computational seismology
SC: Seismology [S]
MN: 2007 Fall Meeting