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Earthquake Rupture Simulations on Faults with Different Degrees of Cementation

Description: 

Earthquakes are usually modeled as a frictional instability propagating along a preexisting weakness plane. The evolution of shear stress with fault slip is described by failure parameterizations obtained from frictional experiments e.g., slip-weakening or rate-and-state friction. While this modeling approach is appropriate for some tectonic faults, induced earthquakes and earthquakes happening on faults with significant degrees of interseismic healing might require different failure parameterizations taking fault cementation into account.

Here we investigate how the cementation degree of fault gouge affects fault failure parameterization and earthquake rupture properties. Previously, Casas et al. (2022) performed direct shear discrete element simulations with different percentages of cementation prescribed within the fault gouge (i.e. different contact laws between particles) and found that increasing cementation enhances the maximum shear strength and gouge brittleness, increases the fracture energy magnitude, and changes the shape of the failure parameterization from smooth curves with pronounced strengthening and single weakening to sharper double weakening curves. To understand how these failure parameterizations affect macroscopic earthquake observables, we derive analytical equations that approximate the numerically obtained curves and use them in finite element simulations of earthquake ruptures. We model earthquake nucleation quasi-statically and the coseismic phase of the earthquake rupture dynamically. We find that surfaces with lower degrees of cementation accumulate substantial magnitudes of slip of significant lateral extent during earthquake nucleation, unlike higher cementation surfaces that produce negligible preseimic slip. Dynamic models of coseismic phase show differences in cumulative slip, maximum slip rate, and earthquake spectra which are related to the differences in stress drop and fracture energy of the different failure parameterizations.

Session: Numerical Modeling in Seismology: Developments and Applications [Poster]

Type: Poster

Date: 4/20/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Ekaterina Bolotskaya

Student Presenter: No

Invited Presentation: 

Authors