Physics-Based Simulations of Aftershock Productivity From Explosion and Earthquake Sources

Date: 4/24/2019

Time: 06:00 PM

Room: Grand Ballroom

Previous observation-based studies suggest that the statistical properties and productivity of aftershocks triggered by explosions may be distinctly different compared to aftershocks triggered by equivalent magnitude earthquakes (Ryall and Savage, 1969; Jarpe et al., 1994; Gross, 1996; Ford and Walter, 2010; Ford and Labak, 2016). Recent numerical experiments suggest that early aftershocks primarily occur during the passage of dynamic stress waves, which are at least an order of magnitude smaller following purely isotropic explosions than those generated by a double-couple earthquake (Kroll et al., 2018). Kroll et al., (2018) also showed that the location and kinematics of potential receiver faults (that host aftershocks) plays a significant role in aftershock generation. Receiver faults located in the direction where the first pulse of explosion generated Coulomb stress change is positive tend to generate robust aftershock sequences, whereas receiver faults in the opposite direction (where the first pulse of Coulomb stress change is negative) tend to remain seismically quiet. Here, we continue these numerical experiments to compare aftershocks productivity from explosions and earthquakes. While the occurrence of aftershocks depends on several factors, for this analysis, we focus our effort at understanding the effects of receiver fault location and kinematics. These experiments employ a 3D seismic wave propagation code, SW4, to compute the static and dynamic stresses that result from each source in a volume. Synthetic aftershocks are generated with the 3D physics-based earthquake simulator, RSQSim. The SW4 stress perturbations are projected onto each receiver fault which is loaded only with stochastically generated random pre-existing shear stress. Statistical properties of each synthetic aftershock sequence related to both source types are compared in terms of productivity, maximum aftershock magnitude, Omori decay rate, and the spatiotemporal relationship between stress changes and event locations.

Prepared by LLNL under Contract DE-AC52-07NA27344

Presenting Author: Kayla Kroll

Authors