SCEC Award Number 18095 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title The influence of rheology on post-seismic and interseismic deformation on rough faults
Investigator(s)
Name Organization
Eric Daub University of Memphis Eunseo Choi University of Memphis
Other Participants Khurram Aslam (Graduate Student)
SCEC Priorities 3d, 2a, 2d SCEC Groups FARM, SDOT, Geodesy
Report Due Date 03/15/2019 Date Report Submitted 01/24/2020
Project Abstract
 This project is a continuation of a previous project (ID: 17182) funded by SCEC. The main objective is to couple dynamic rupture simulations with long-term tectonic modeling (LTM) to examine how heterogeneous stresses resulting from dynamic earthquake slip on rough faults influence the pattern of post- and inter-seismic strain accumulation. Unlike the previous project that considered only a plain strain model setup with a strike-slip fault at a fixed depth, this project also considers anti-plain depth-dependent models for investigating the strain accumulation patterns around a rough fault. The off-fault materials are governed by continuum plasticity in both the rupture and LTM models, while on-fault failure in the rupture model follows linear slip weakening. We examine the complex stress and damage pattern resulting from slip on a fractal fault, which creates a heterogeneous starting point from which we initiate periods of tectonic loading. Our plain strain model shows that the heterogeneous stresses due to fault roughness lead to localized inter-seismic plastic deformation, though our models show this strain accumulates in a steady manner due to the lack of time-dependent behavior in the continuum plasticity models. Our anti-plain model results suggest that the post-seismic phase in the near-fault region is affected by the heterogeneous stresses due to rupture on a complex fault. The behavior of surface displacement is different for a synthetic GPS station placed in the nearfault region than one placed at far fault region. The displacement rates in near-fault region are also higher within the post-seismic period.
Intellectual Merit The objective of this study is to understand the dynamics of a complete earthquake cycle with complex but realistic initial conditions to get an improved understanding of the earthquake cycle over a broad range of time and length scales. This objective aligns with the principal goal of the SCEC i.e. to examine deformations using observational and computational techniques. This work introduces a new method for examining how fully dynamic fault slip on rough faults influences long-term deformation patterns on strike-slip faults as well as its post-seismic and inter-seismic phase. We couple the results of a spontaneous rupture model with a quasi-static long-term tectonic model, incorporating off-fault plasticity, strain and state dependence in order to examine how damage and stress heterogeneities influence the deformation patterns throughout the seismic cycle. Our research provides new tools for examining how realistic earthquake deformations observed with GPS and InSAR can be compared with numerical models.
Broader Impacts All the phases of an earthquake are important to investigate in order to get a better understanding of the physics of earthquakes and aftershocks nucleation. This investigation is also necessary for the mitigation of earthquake risk. Our work provides new computational methods that examine how loading and deformation processes affect faults over a wide range of length and time scales. Quantifying such processes on realistic fault geometries is essential for generating more accurate forecasts of future events.
Exemplary Figure Sec. 1.3 Exemplary Figure

Caption: Modeling setup used to examine stress changes and postseismic deformation on rough earthquake faults. (a) and (f) show the computationl domain for along-strike and along-depth dynamic rupture models, respectively. (b) and (g) are the computational setups for along-strike and along-depth long-term tectonic models. The rough fault with heterogeneous stress and slip is subjected to further tectonic loading to examine how continued stressing on a heterogeneous fault influences further deformation. (c) Examples of rough fault profiles. (d) Plastic strain field from the dynamic rupture simulation showing that damage occurs primarily on the extensional side of the fault. (e) Plastic strain distribution during an inter-seismic period indicating that coseismically-damaged areas are more susceptible to further deformation and likely to be nucleation locations of future earthquakes. (h) Surface displacement rate throughout the inter-seismic period at synthetic stations present at different distances from the fault for the geotherm of 20 K/km. (i) Same with (h) but for 25 K/km. The heterogeneous initial conditions affect the surface displacement rates at stations with 20 km from the fault for the first 5 years.