Modeling active fault systems and seismic events by using a Fiber Bundle model. Example case: Northridge aftershock sequence

Abstract. Earthquake aftershocks display spatio-temporal correlations arising from their self-organized critical behavior. Dynamic deterministic modeling of aftershock series is difficult to carry out due to both the physical complexity and uncertainties related to the different parameters which govern the system. Nevertheless, numerical simulations with the help of stochastical models such as the Fiber Bundle (FBM) permit the use of an analog of the physical model that produces a statistical behavior with many similarities with real series. FBM are simple discrete element models that can be characterized by using few parameters. In this work, a new model based on FBM that includes geometrical faults systems is proposed. Our analysis focuses on aftershock statistics in space, time and magnitude domains. To analyze the model behavior a parametric study is carried out. Moreover, we analyzed the synthetic aftershock sequences properties assuming initial load configurations and suitable conditions to propagate the rupture. As an example case, we have modeled a set of real active faults related to the Northridge, California, earthquake sequence. We compare the simulation results to statistical characteristics from the Northridge sequence determining which range of parameters in our FBM version reproduce the main features observed in real aftershock series. In order to reproduce statistical characteristics of the real sequence larger π frac values (0.85  frac P (0.0  P  l 0.08) are needed. This implies the important corollary that a very small departure from an initial random load configuration (computed by P ), and also a large difference between the load transfer from on-fault segments than by off-faults (computed by π frac ), is required to initiate a rupture sequence which conforms to observed statistical properties such as the Gutenberg-Richter law, Omori law and fractal dimension.