SCEC Award Number 18098 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Toward Full Waveform Tomography Across California
Name Organization
Carl Tape University of Alaska, Fairbanks Clifford Thurber University of Wisconsin, Madison
Other Participants Vipul Silwal, U. Alaska postdoc
Avinash Nayak, U. Wisconsin postdoc
SCEC Priorities 4a, 3a, 3b SCEC Groups CXM, CME, Seismology
Report Due Date 03/15/2019 Date Report Submitted 03/17/2019
Project Abstract
We seek to establish a complete, open-source software workfow for simulation-based seismic inversion in southern California. Our goal is to establish seismic imaging tools that are documented and usable by a broader group of seismologists. This would provide a sustainable pathway to validating and updating the SCEC Community Velocity Models (CVMs), such as CVM-H15.1 and CVM-S4.26, which are used for probabilistic ground motion simulation projects such as CyberShake. Earthquakes and ambient noise cross-correlations can both be used for seismic imaging. To start this effort, we focus on extracting the CVMs using UCVM software, choosing a small target set of earthquakes and ambient noise “master stations,” performing moment tensor inversions, and establishing a semi-automated 3D synthetic inversion using a software package called seisfows. Also, using classical tomography approaches, we improve upon the tomographic models in central California and aim to use these models within future simulation-based inversions.
Intellectual Merit We are promoting the use of highly accurate seismic wavefield simulations for the purposes of ground motion predictions and for improving our 3D tomographic models of southern California. Simulation- and adjoint-bases seismic inversion remains a formidable challenge, and we are seeking to reduce the effort by establishing a new workflow.
Broader Impacts Our emphasis on open-source software is a key component that will allow the broadest range of seismologists to benefit from our work. In addition to using open-source software, we aim to provide suitable documentation, with the hope of attracting and sustaining users.

The project initiated a fruitful collaboration between UAF and U.~Wisconsin and also fostered the development of three postdocs new to the SCEC community: Avinash Nayak, Ryan Modrak, and Vipul Silwal. Team members (Tape, Thurber, Nayak) participated in the SCEC CVM workshop in Pomona in October 2018, and also interacted with UCVM software developers over the course of the project.
Exemplary Figure Figure 1 from report.
Caption: (a) Vs at depth 18 km estimated using the revised body-wave dataset and TOMODD with the Vp/Vs ratio constraint, compared to the Lin et al. (2010) model shown in (b). (c) Vs at depth 0.5 km from joint inversion of the revised body-wave dataset and ambient noise derived Rayleigh-wave phase velocity dispersion measurements compared to model CCA6 shown in (d).
Credit: Avinash Nayak