GTDef: An Open-Source Dislocation Modeling Toolset

Abstract:

Over the past quarter century, substantial development and densification of geodetic data, including GNSS and InSAR, have made robust and easy-to-use deformation modeling software much more necessary. With this, several analytical and numerical methods for modeling such data have been developed, specifically for providing better understanding of crustal deformation mechanisms. Here we present GTDef, which is a set of algorithms developed in MATLAB that can incorporate a wide range of geodetic data types to model deformation observed on the Earth’s surface. The primary algorithms are built based on Okada (1985)’s parameterization of deformation from rectangular dislocations within an elastic homogeneous half-space, and additionally includes codes for building Green’s functions in stratified non-homogeneous half-space (following Wang et al., 2013). GTDef is designed to perform both forward and inverse models, the latter using a bounded linear least-squares method. Working on distributed simple faults, the inversion method can discretize a fault into patches that minimize roughness with a range of user-chosen smoothing kernels (following Jónsson et al., 2002). Additionally, GTDef has built-in capabilities to perform detailed analysis of model resolution, including tools for “checkerboard tests” and evaluation of model resolution directly from the resolution matrix developed during an inversion. These tools are necessary to properly interpret model results. In addition to internal methods, the codes can ingest external Green’s functions (e.g. seismic or tsunami wavefield solutions, results from Finite-Element models), optimally-discretize InSAR data, and perform independent data weighting. Finally, a number of GMT-based (Wessel et al., 2019) imaging programs are included. The open-source software will be available for download through GitHub (https://github.com/avnewman/GTDef).