Fast, accurate solutions for curvilinear earthquake faults and anelastic strain

TL;DR

This paper introduces advanced numerical techniques and software enhancements for high-precision modeling of deformation and stress around curvilinear faults and anelastic strain volumes in Earth's heterogeneous elastic half-space, improving accuracy and speed.

Contribution

The authors develop and demonstrate new numerical methods and software for rapid, accurate modeling of complex fault geometries and anelastic strain in Earth's crust and lithosphere.

Findings

Validated the method with analytic tests.

Achieved high-precision modeling of the 2015 Nepal earthquake deformation.

Enhanced software Gamra for complex fault and strain volume modeling.

Abstract

Imaging the anelastic deformation within the crust and lithosphere using surface geophysical data remains a significant challenge in part due to the wide range of physical processes operating at different depths and to various levels of localization that they embody. Models of Earth's elastic properties from seismological imaging combined with geodetic modeling may form the basis of comprehensive rheological models of Earth's interior. However, representing the structural complexity of faults and shear zones in numerical models of deformation still constitutes a major difficulty. Here, we present numerical techniques for high-precision models of deformation and stress around both curvilinear faults and volumes undergoing anelastic (irreversible) strain in a heterogenous elastic half-space. To that end, we enhance the software Gamra to model triangular and rectangular fault patches and tetrahedral and cuboidal strain volumes. This affords a means of rapid and accurate calculations of elasto-static Green's functions for localized (e.g., faulting) and distributed (e.g., viscoelastic) deformation in Earth's crust and lithosphere. We demonstrate the correctness of the method with analytic tests, and we illustrate its practical performance by solving for coseismic and postseismic deformation following the 2015 Mw 7.8 Gorkha, Nepal earthquake to extremely high precision.