Journal of Conference Abstracts

Gutenberg Richter and Characteristic Earthquake Behavior in Simple Mean Field Models of Heterogenous Faults

Karin Dahmen (dahmen@cmt.harvard.edu)¹, Deniz Ertas (mdertas@erenj.com)², Yehuda Ben-Zion (benzion@topaz.usc.edu)³ & Daniel S. Fisher (fisher@cmt.harvard.edu)¹

¹Dept. of Physics, Harvard University, Cambridge, MA, 02138, U.S.A.

²Exxon Research and Engineering, Clinton Twp, Rte22 East, Anandale, New Jersey, 08801, U.S.A.

³Department of Earth Sciences, Univ. of Southern CA, Los Angeles, CA, 90089-0740, U.S.A.

The statistics of earthquakes in a heterogeneous fault zone is studied analytically and numerically in a mean field version of a model for a segemented fault system in a three-dimensional elastic solid (Fisher et al., 1997), focusing on the interplay between the roles of disorder, dynamical effects, and driving mechanisms. A two-parameter phase diagram is found, spanned by the amplitude of dynamical weakening (or "overshoot") effects (epsilon) and the normal distance L of the driving forces from the fault. In general, small (epsilon) and small L are found to produce Gutenberg-Richter type power law statistics with an exponential cutoff, while large (epsilon) and large L lead to a distribution of small events combined with characteristic system-size events. In a certain parameter regime nucleation from one phase to the other is possible on time scales determined by the fault size and other model parameters. The implications to observed earthquake statistics are discussed.

Fisher DS, Dahmen K, Ramanathan S & Ben-Zion Y, Phys. Rev. Lett. 78, 4885, (1997)