HR: 1340h
AN: S43B-1073    [Abstracts]
TI: Correlating Aftershock Hypocenters With On-fault Main Shock Properties: Introducing Non-standard Statistical Tests
AU: * Woessner, J
EM: j.woessner@sed.ethz.ch
AF: ETH Zurich, Swiss Seismological Service, HPP P3 Schafmattstr. 30, Zurich, 8093 Switzerland
AU: Schorlemmer, D
EM: danijel@sed.ethz.ch
AF: ETH Zurich, Swiss Seismological Service, HPP P3 Schafmattstr. 30, Zurich, 8093 Switzerland
AU: Wiemer, S
EM: s.wiemer@sed.ethz.ch
AF: ETH Zurich, Swiss Seismological Service, HPP P3 Schafmattstr. 30, Zurich, 8093 Switzerland
AU: Mai, P M
EM: m.mai@sed.ethz.ch
AF: ETH Zurich, Swiss Seismological Service, HPP P3 Schafmattstr. 30, Zurich, 8093 Switzerland
AB: Quantitatively correlating properties of finite-fault source models with hypocenters of aftershocks may provide new insight in the relationship between either slip or static stress change distributions and aftershock occurrence. We present advanced non-standard statistical test approaches to evaluate the test hypotheses (1) if aftershocks are preferentially located in areas of low slip and (2) if aftershocks are located in increased shear stress against the null hypothesis: aftershocks are located randomly on the fault plane. By using multiple test approaches, we investigate possible pitfalls and the information content of statistical testing. To perform the tests, we use earthquakes for which multiple finite-fault source models and earthquake catalogs of varying accuracy exist. The aftershock hypocenters are projected onto the main-shock rupture plane and uncertainties are accounted for by simulating hypocenter locations in the given error bounds. For the statistical tests, we retain the spatial clustering of earthquakes as the most important observed features of seismicity and synthesize random slip distributions with different approaches: first, using standard statistical methods that randomize the obtained finite-fault source model values and second, using a random spatial field model. We then determine the number of aftershocks in low-slip or increased shear-stress regions for simulated slip distributions, and compare those to the measurements obtained for finite-source slip inversions. We apply the tests to prominent earthquakes in California and Japan and find statistical significant evidence that aftershocks are preferentially located in low-slip regions. The tests, however, show a lower significance for the correlation with the shear-stress distribution, but are in general agreement with the expectations of the asperity model. Tests using the hypocenters of relocated catalogs show higher significances.
DE: 7215 Earthquake source observations (1240)
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