SCEC Award Number 15058 View PDF
Proposal Category Travel Only Proposal (SCEC Annual Meeting)
Proposal Title Continued Development of Workflows and Packages for Using Finite Element Models for Geodetic Inversions
Name Organization
Charles Williams GNS Science (New Zealand)
Other Participants
SCEC Priorities 1e, 1b, 5d SCEC Groups CS, Geodesy, SDOT
Report Due Date 10/16/2015 Date Report Submitted 10/14/2015
Project Abstract
In previous work (Williams and Wallace, 2015) we used Green’s functions generated with the PyLith finite element code (Aagaard et al., 2013) to examine the effects of material heterogeneity on geodetic inversions of slow slip events (SSEs) along the Hikurangi Margin, New Zealand. We are extending this work to include interseismic coupling models for the North Island of New Zealand. For both of these projects we have used PyLith to generate Green’s functions and Defnode (McCaffrey, 1995; 2002) to perform geodetic inversions. We have developed a workflow that allows us to perform the necessary tasks in a semi-automated way.
The most difficult task is mesh generation. We have developed Python scripts to create geometry for use with the Trelis meshing package, using nodal information from Defnode. Additional scripts generate an initial mesh, impose a user- defined sizing function, and create a refined mesh suitable for generating Green’s functions. We generate Green’s functions with PyLith, and integrate them to provide the Green’s functions required by Defnode. Once the Defnode Green’s functions have been generated we use another script to launch many Defnode inversions in parallel. We are still improving our workflow, and once it is finished it will be publicly available. Our initial research has shown that using material properties from a seismic velocity model can have significant effects on predicted SSE slip distributions, and the same is likely true for interseismic coupling models. The workflow that we are developing should allow others to explore these effects in other regions.
Intellectual Merit This project is relevant to SCEC’s goal of constraining fault slip with geodetic data. It provides a method for using several of SCEC’s other projects, such as the CFM, the CVM, and the Community Geodetic Model, to provide more accurate interpretations of coseismic and interseismic fault slip. It also makes use of the PyLith finite element code, which has received support from SCEC in the past, as well as the DEFNODE geodetic inversion code.
Broader Impacts The workflow developed as part of this project will be made publicly available, and should thus help other scientists to make use of more realistic elastic properties and include topographic effects in their own research. The resulting improved slip distributions should enhance our seismic hazard capabilities.
Exemplary Figure Last figure on bottom left in the poster pasted into this document. This figure represents the integration procedure used to go from PyLith-generated Green’s functions to Green’s function suitable for use with DEFNODE.