Earthquake Recurrence in Simulated Fault Systems

Abstract

Abstract-We employ a computationally efficient fault system earthquake simulator, RSQSim, to explore effects of earthquake nucleation and fault system geometry on earthquake occurrence. The simulations incorporate rate-and state-dependent friction, high-resolution representations of fault systems, and quasi-dynamic rupture propagation. Faults are represented as continuous planar surfaces, surfaces with a random fractal roughness, and discontinuous fractally segmented faults. Simulated earthquake catalogs have up to 10 6 earthquakes that span a magnitude range from *M4.5 to M8. The seismicity has strong temporal and spatial clustering in the form of foreshocks and aftershocks and occasional large-earthquake pairs. Fault system geometry plays the primary role in establishing the characteristics of stress evolution that control earthquake recurrence statistics. Empirical density distributions of earthquake recurrence times at a specific point on a fault depend strongly on magnitude and take a variety of complex forms that change with position within the fault system. Because fault system geometry is an observable that greatly impacts recurrence statistics, we propose using fault system earthquake simulators to define the empirical probability density distributions for use in regional assessments of earthquake probabilities.

Location of largest earthquake slip and fast rupture controlled by along‐strike change in fault structural maturity due to fault growth

“…Another fundamental property of faults is their along‐strike segmentation. Faults are divided along their length into discrete subparallel segments of different sizes separated by geometrical discontinuities, generally step overs, called “intersegments” [e.g., Segall and Pollard , ; Sibson , ; Barka and Kadinsky‐Cade , ; Aydin and Schultz , ; Peacock , ; Walsh et al ., ; Manighetti et al ., , ; De Joussineau and Aydin , ; Dieterich and Richards‐Dinger , ; Giba et al ., ]. At least the largest intersegments, which separate the longest fault segments, are of crustal scale [e.g., Sibson , ; Allam and Ben‐Zion , ; Valoroso et al ., ; Allam et al ., ].…”

“…This is commonly described as the accumulation of slip leading to a geometrically simpler fault [e.g., Wesnousky , ; Ben‐Zion and Sammis , ; King and Wesnousky , ; Wechsler et al ., ]. The evolution of on‐fault slip at intersegments shows that immature intersegments, where on‐fault slip deficit is pronounced, are zones of high fault strength which likely act as mechanical barriers to earthquake slip (e.g., Scholz and Lawler [], Dieterich and Richards‐Dinger [], and Allam et al . []; for a theoretical definition of earthquake barriers, see Das and Aki [], Nur [], and Boatwright and Cocco []), whereas more mature intersegments, where on‐fault slip deficit is reduced, have a lower strength.…”

Modeling Injection‐Induced Seismicity with the Physics‐Based Earthquake Simulator RSQSim

“…RSQSim is a computationally efficient 3D boundary-element code that incorporates rate-state fault friction to simulate long sequences of earthquakes in interacting fault systems. Although RSQSim (Dieterich and Richards-Dinger, 2010;RichardsDinger and Dieterich, 2012) was specifically developed for efficient simulations of earthquakes and other fault slip processes in geometrically complex fault systems, our initial investigation reported here focuses on the characteristics of induced earthquakes arising from injection near a single isolated planar fault.…”

Deterministic model of earthquake clustering shows reduced stress drops for nearby aftershocks

“…Our new physical model is based on a generalization of an extremely efficient quasi‐static boundary element model developed by Dieterich and Richards‐Dinger []. Some details of the model and its approximations are presented in the supporting information; a key aspect is that it preserves the fundamental features of the rate and state friction equations, which lead to delayed time‐to‐failure nucleation effects and temporal clustering [ Dieterich , ].…”