Optimizing Numerical Simulations of Earthquake Sequences Including Off-Fault Viscoelastic Deformation using Hierarchical Matrices

Joseph Wick, & Valere R. Lambert

Published August 16, 2021, SCEC Contribution #11568, 2021 SCEC Annual Meeting Poster #166

Deformation along faults is observed to be highly localized within Earth’s upper crust, although less is known about the nature of fault shear zones at depth. Simulations of sequences of earthquakes and aseismic slip (SEAS) can provide insight into the rheology of the crust and upper mantle, which is important for understanding the loading of stress on faults, the recurrence and depth-extent of earthquake ruptures, and the general state of stress within the lithosphere. Analytic solutions for stress as a function of distributed deformation allow for the efficient inclusion of bulk deformation in numeric simulations using the boundary integral method (Lambert and Barbot, GRL 2016, Barbot GRL 2018). However, explicitly incorporating inelastic off fault deformation into long term numerical simulations remains challenging as the computational time of a straightforward boundary integral method (BIM) implementation scales quadratically with the number of computational elements. A number of studies have developed methods to optimize BIM, including the use of hierarchical matrices to approximate the relationship between deformation and stress. Here, we explore the use of hierarchical matrices to optimize quasi-dynamic SEAS simulations that include off-fault viscoelastic deformation using the integral method with the goal of considering bulk viscoelastic deformation in large-scale studies of long term fault processes, including 3D SEAS simulations and models of fault networks. 

Key Words
Viscoelastic, SEAS, Earthquake Sequences, Hierarchal Matrices

Citation
Wick, J., & Lambert, V. R. (2021, 08). Optimizing Numerical Simulations of Earthquake Sequences Including Off-Fault Viscoelastic Deformation using Hierarchical Matrices. Poster Presentation at 2021 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)