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Linking Geodynamic-Seismic Cycling Models With Earthquake Dynamic Rupture Models: 5 Choices to Consider

Description: 

By linking a subduction zone geodynamics and seismic cycling model (SCM) to a dynamic earthquake rupture model (EQM), we produce a realistic megathrust earthquake from initial conditions that are physically consistent with one another and long term subduction. The SCM (van Dinther et al. 2013, 2014) begins with a geodynamics phase, then transitions to a seismic cycle phase in which slip instabilities arise spontaneously without a prescribed fault. The material properties, stress field and fault strength parameters at the start of one SCM slip event are mapped to the EQM. The fault geometry is set a priori in the EQM using the locations of maximum strain rate over the entire SCM slip event. The EQM is run with SeisSol (Pelties et al. 2012, 2014), which captures the complete rupture dynamics and seismic wave propagation. We highlight certain linking choices for discussion and future consideration: (1) 2D to 3D mapping: We assume that the fault geometry, material properties, stress and frictional parameters from the 2D SCM are constant in the along-strike direction in the 3D EQM, a technically simple approach that likely does not reflect subduction zone characteristics. (2) Poisson’s ratio, ν: The SCM assumes incompressible rock with ν = 0.5, which is valid over long time frames, but not appropriate for modeling earthquake rupture dynamics. We choose ν = 0.25 for the EQM, but note that v influences slip magnitudes. (3) Static fault strength: We assume that the effective mean stress in the SCM is equivalent to the effective normal traction along the EQM fault, which appears appropriate up to ~30 km depth in these models, but alternatives could be considered. (4) Frictional weakening: Coseismic weakening is better modeled in the EQM than in the SCM, challenging our use of the SCM to assign dynamic coefficients of friction and slip-weakening distances. In addition, the SCM includes rate-strengthening in shallow sediments, which is honored in the EQM only by varying the coefficients of dynamic friction here. (5) The topography developed during the SCM is not mapped to the EQM.

Session: From Geodynamics to Earthquake Rupture, Models That Cross Time- and Length-Scales - I

Type: Oral

Date: 5/3/2024

Presentation Time: 04:30 PM (local time)

Presenting Author: Elizabeth

Student Presenter: No

Invited Presentation: Yes

Authors