Seismicity, Fault Slip Rates, and Fault Interactions in a Fault System

Abstract

Seismicity and the partitioning of slip rates in interacting and mechanically coupled fault systems are poorly understood. We developed and used three‐dimensional viscoelastoplastic finite element models to simulate earthquakes, earthquake cycles, and synthetic seismicity in single and bifurcated fault systems and investigate seismicity, fault slip rates, and interactions and mechanical coupling between faults in fault systems. The modeled interseismic velocities and coseismic displacements are consistent with those from analytical and quasi‐analytical solutions. We found that the modeled frequency‐magnitude relation satisfies the Gutenberg‐Richter relation and the b value is inversely related to differential stress. We observed that the seismicity on two parallel faults is often interdependent and complementary: high seismic moment release rates on a fault are usually accompanied by low ones on the other fault and vice versa; the two faults collectively accommodate far‐field tectonic loading and crustal relative motion. Model results showed that when two parallel faults have the same or similar strength, they have similar seismicity and long‐term slip rates, but when one of the two faults has lower strength, it has more active seismicity and a faster slip rate than the other; the sum of their slip rates equals the far‐field crustal relative motion in both cases. The results in this study provide scientific insights into the spatiotemporal migration of seismicity and partitioning of fault slip rates in an interacting and mechanically coupled fault system and help to qualify b values and to evaluate the earthquake hazard and risk on each of the faults in such a system.

Seismic Hazards Along the Longmen Shan Fault: Insights from Stress Transfer Between Major Earthquakes and Regional b-Values

“…The b value has attracted a great deal of attention (Kun et al, 2013;Liu & Pei, 2017;Main et al, 1992;Scholz, 1968;Schorlemmer et al, 2005). Rock fracture experiments (Main et al, 1992;Scholz, 1968), numerical simulation (Gao et al, 2020), and statistical results of regional seismicity (Kun et al, 2013;Schorlemmer et al, 2005) all infer that b value has a clear physical meaning: a lower b value indicates a higher stress level in a region, while a higher b value indicates a lower stress level in a region. Thus, we then calculate the regional b value to further estimate the stress level in the eastern Tibetan Plateau before the 2008 Mw7.9 Wenchuan earthquake.…”

Long Short-Term Memory Networks for Pattern Recognition of Synthetical Complete Earthquake Catalog

“…We ran the model a quasi-steady state after integrating for about 100,000 years (Figure 2a-c) until the regional stress patterns stabilized and the stress fluctuated around the background stress field as the result of earthquakes (modified from [34]). The predicted background stress was validated by its consistency with the regional stress field indicated by earthquake focal mechanisms [30].…”

“…We used a fault element with a width of 2 km to simulate the fault with a dip angle of 90 degrees; the fault depth was a 20 km fault, and the element was a special kind of element with strain-softening elasto-plasticity (Figure 1b). There was a crust on the outside over the fault simulation elastoplastic material, and the lower crust and upper mantle is modelled by the Maxwell's rheology viscosity [30,33] (The model is modified from [34]). The main material of the model parameters is listed in Table 1.…”