Shallow Slip Deficit, Slip Pulses and Event Complexity in a Model of Seismic Cycle with Low Velocity Fault Zones

Session: Exploring Rupture Dynamics and Seismic Wave Propagation Along Complex Fault Systems
Type: Oral
Date: 4/29/2020
Time: 04:30 PM
Room: 110 + 140
Description: 

Modeling earthquake ruptures is a complex challenge due to the eclectic sources of nonlinearities and heterogeneities, in addition to the multi-scale nature of the problem, both spatially and temporally. Here, we present a hybrid numerical scheme (FEBI) that combines finite element method (FEM) and spectral boundary integral method (SBIM) to simulate earthquake cycles with rate and state fault subjected to slow tectonic loading processes of long duration intermittent by episodes of dynamic fracture in the presence of near-field heterogeneity. FEBI benefits from the flexibility of FEM in handling nonlinear problems, while retaining superior computational performance associated with SBIM. The different time scales are resolved through an alternating quasi-dynamic and dynamic approach. The long interseismic phases are modelled using a quasi-dynamic approximation allowing for larger time steps, while for dynamic rupture an explicit time stepping algorithm is utilized to capture wave propagation properties within the media. The numerical scheme is validated using a benchmark problem proposed by Southern California Earthquake Center (SCEC) for sequence of earthquakes and aseismic slip (SEAS). The proposed scheme is then utilized in studying SEAS beyond homogenous media to model a fault embedded in a low velocity fault zone (LVFZ). The impact of the LVFZ in altering the earthquake cycle is highlighted. Specifically, fault ruptures within LVFZ produces sub-surface events that fail to propagate to the free surface and produces residual stresses which impact subsequent ruptures resulting in larger slip rates. Furthermore, wave reflections due to the existence of LVFZ contributes toward the generation of pulse like ruptures that are absent from the homogenous case. Finally, we comment on the overall changes to the earthquake patterns in the presence of LVFZ such as interevent times, event patterns and magnitude scaling.

Presenting Author: Mohamed Abdelmeguid

Authors