SCEC Award Number 16193 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
Investigator(s)
Name Organization
Charles Williams GNS Science (New Zealand)
Other Participants
SCEC Priorities 1e, 5d, 1b SCEC Groups SDOT, CS, Geodesy
Report Due Date 10/14/2016 Date Report Submitted 11/05/2018
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 in several ways to solve for interseismic coupling on the North Island of New Zealand using PyLith-generated Green’s functions with Defnode and TDefnode (McCaffrey, 1995; 2002), solving for shallow slow slip along the Hikurangi Margin using PyLith-generated Green’s functions and our own inversion code (Williams and Wallace, 2018), and solving for time-varying slip along the Hikurangi and Cascadia margins using PyLith-generated Green’s functions with the Network Inversion Filter (NIF). We have developed workflows that allow us to perform all of these tasks in a semi-automated way.
We have developed Python scripts to create geometry for use with the Trelis meshing package, using nodal information from Defnode/TDefnode or the NIF. Additional scripts generate an initial mesh, impose a user-defined sizing function, and create refined meshes suitable for generating Green’s functions. We generate Green’s functions with PyLith and integrate them to provide Green’s functions for Defnode, the NIF, or our own inversion code. Our 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, (CFM, CVM, 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 and NIF geodetic inversion codes.
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 Figure 2 from the Technical Summary. This figure summarizes the results of Williams and Wallace (2018).