Advances in Numerical Modeling of Microseismicity

A simple technique is presented for extracting seismic information from slip on faults in distinct element models. It is shown that a simple static-dynamic friction law is sufficient to induce instability, and therefore produce seismic events. With this approach, all slips are seismic since the drop in frictional resistance is always faster than the drop in loading. In reality, not all events are seismic and the condition for instability depends on the system stiffness, fault roughness and normal stress. To simplify the problem, it is proposed that a user-defined minimum normal stress is required in the models for slips to be considered seismic. The method is shown to produce realistic behavior when simulating a laboratory experiment of slip on a single fault. A field-scale model with multiple intersecting faults is also presented. Seismicity is recorded and magnitudes are realistic, but more investigation is required before this method can be used in realistic field-scale modeling.