SCEC Award Number 13044 View PDF
Proposal Category Travel Only Proposal (SCEC Annual Meeting)
Proposal Title Continued Benchmarking of Codes for Crustal Deformation Modeling
Investigator(s)
Name Organization
Charles Williams GNS Science (New Zealand) Susan Ellis GNS Science (New Zealand)
Other Participants Sylvain Barbot, Earth Observatory of Singapore, Nanyang Techonogical University; Andy Freed, Purdue University; Mong-Han Huang, Univeristy of California, Berkeley; David Sandwell, University of California, San Diego; Bridget Konter-Smith, University of Texas, El Paso
SCEC Priorities 1e, 1b, 2e SCEC Groups SDOT, CS, FARM
Report Due Date 03/15/2014 Date Report Submitted N/A
Project Abstract
 The overall goal of this project was to provide benchmark results for a variety of deformation modeling codes, as well as the elastic analytical solution of Okada [1992]. Due to a variety of reasons, we needed to restrict ourselves to a narrower range of problems. We focussed on optimizing the comparison between PyLith and the analytical Okada solution, and devising a workflow for using PyLith in a geodetic inversion scheme. This reduces our dependence on external collaborators, and also helps align our work with that of the SCEC geodetic community. The advantages of using a finite element method for geodetic inversions are that we can take advantage of information on material inhomogeneities, such as that provided by the SCEC CVM-H. The finite element method can also include topographic effects in regions where there is significant topography.

We have developed a variety of methods for producing an optimized mesh for comparison to known solutions. Our preferred method at present involves computing an initial solution on a coarse mesh, and then using a sizing function based on the gradient of the strain energy. We have developed Python scripts that may be used in conjunction with Cubit/Trelis (www.csimsoft.com) to produce these optimized meshes. We have also developed a simple inversion framework to compare Okada-based inversions with PyLith-based inversions, and have begun exploring the effects of material inhomogeneity on geodetic inversions. All materials will be available as part of the PyLith package and will also be used as training materials at SCEC-sponsored workshops.
Intellectual Merit This project explores the fundamental nature of geodetic inversions of fault slip, focusing on the aspects that are neglected by traditional half-space models (e.g., material inhomogeneities and topography). In addition to exploring solution accuracy and inversion techniques, the project provides freely-available tools for use by other scientists.
Broader Impacts As mentioned previously, this project provides tools for both mesh generation and inversions of geodetic data, which will help other scientists in their research. These tools will also be used as training material at SCEC-sponsored workshops (e.g., the 2014 Crustal Deformation Modeling workshop in Palo Alto), and will be provided as part of the PyLith finite element modeling package.
Exemplary Figure Figure 1. Computed ground surface displacements for Okada solution (red arrows) and PyLith solution (blue arrows) for the case of a 45 degree buried reverse fault with uniform slip. Colored dots show the vector norm percent difference between the two solutions. (a) Uniform resolution mesh. (b) Mesh created using an ellipsoidal sizing function. (c) Mesh created using a sizing function based on the strain energy gradient for a coarse resolution solution.