HR: 1340h
AN: NG33A-0166    [Abstracts]
TI: Patterns of Co-seismic Crustal Strain Release Associated With Different Earthquake Sizes Imaged by a Tensor Summation Method
AU: * Bailey, I W
EM: iwbailey@usc.edu
AF: University of Southern California, Department of Earth Sciences 3651 Trousdale Pkwy (ZHS117), Los Angeles, CA 90089 United States
AU: Becker, T W
EM: twb@usc.edu
AF: University of Southern California, Department of Earth Sciences 3651 Trousdale Pkwy (ZHS117), Los Angeles, CA 90089 United States
AU: Ben-Zion, Y
EM: benzion@usc.edu
AF: University of Southern California, Department of Earth Sciences 3651 Trousdale Pkwy (ZHS117), Los Angeles, CA 90089 United States
AB: We use a method of summing tensors of potency (moment divided by rigidity) to study the temporal and spatial patterns of co-seismic strain release in southern California. Potency tensors are calculated for individual earthquakes from catalog data, using an empirical potency-magnitude scaling relation, and we specifically target small events. By focusing directly on the smaller events and not performing inversions, we are able to analyze a large data set, while minimizing assumptions that may affect the results and obscure finer details. We then proceed to examine the cases for or against existence of fixed finite length scales related to the strain release patterns, which are often assumed in inversion studies. Here, we focus on effects of earthquake and binning sizes with regards to the results of the summing process. A summation that takes into account the scalar potency of each event will lead to a dominance of large events on the final results, while neglecting this information will be less correct physically and lead to a dominance of the more numerous smaller events. Concentrating on five spatially defined 'bins', chosen to contain a sufficient number of data and come from a range of tectonic regions in southern California (e.g. the Eastern California Shear Zone and the San Jacinto Fault zone), we observe how the summation process can be affected by constraints imposed with regard to the size of events. We show how the results can fluctuate as a function of (i) number of events summed, (ii) region of spatial averaging (i.e. bin size), (iii) restricting the upper and lower magnitude for events summed, and (iv) whether the events are weighted by their scalar potency or not. A similar degree of heterogeneity is observed at all scales, concurring with previous studies and implying a scale-invariant behavior. We examine the possibility that these observations are a function of errors in the catalog data by varying quality requirements for the catalog used, as well as analyzing in detail the potential artifacts associated with our analysis procedure.
DE: 4440 Fractals and multifractals
DE: 4460 Pattern formation
DE: 8118 Dynamics and mechanics of faulting (8004)
DE: 8164 Stresses: crust and lithosphere
SC: Nonlinear Geophysics [NG]
MN: Fall Meeting 2005