SCEC Award Number 24043 View PDF
Proposal Category Individual Research Project (Single Investigator / Institution)
Proposal Title 3D full waveform inversion of the Salton Seismic Imaging Project active source dataset
Investigator(s)
Name Organization
Rasheed Ajala Columbia University Folarin Kolawole Columbia University
SCEC Milestones A1-1, A2-1, A3-6 SCEC Groups CEM, Seismology, GM
Report Due Date 03/15/2025 Date Report Submitted 03/15/2025
Project Abstract
 With the advent of computational algorithms to synthesize multiscale seismic wave speed models of the Earth, a physics-based approach for ground motion prediction is slowly becoming a reality. Seismic imagers and developers can work on developing small-scale models in the most earthquake-hazardous regions and develop high-frequency models exceeding 1 Hz that are of interest to structural engineers. This approach is more tractable than working on a regional scale; once the models are developed, they can be merged into any existing long-wavelength model for enhanced coverage. Here, we focus on developing a high-frequency (up to 5 Hz) structural model for the southernmost section of the San Andreas fault in Salton Trough using previously acquired active source data. Though local in scale, the computational expense of the inversion is still great. Thus, extreme caution is required in selecting all the proper optimization parameters to reduce computational costs and promote reproducibility. This report focuses on our progress involving the open-source implementation of the optimal transport misfit functional (Wasserstein norm) currently being used in the model updates to address previous inversion challenges – low-frequency starting models and noisy waveforms.
SCEC Community Models Used Community Velocity Model (CVM)
Usage Description The current project focuses on updating structural Earth models in the vicinity of the southern San Andreas fault. Toward this goal, we are utilizing a hybrid model comprising the CVM-H 15.1, CV-LSU, and IV-LSU CVMs as starting models in the optimization.
Intellectual Merit We aim to develop the first 3D high-frequency Earth model in Salton Trough that utilizes active-source waveform data with frequencies up to 5 Hz. The results will have details that will be useful for seismic hazard assessment by satisfying structural engineers' frequency requirement and will also be imperative in further understanding transtensional tectonics in the region. The project's research goals align with SCEC science milestones A1-1, A2-1, and A3-6.
Broader Impacts The broader impact of the work comprises three components: 1) Societal Impact. Products developed from the project will significantly benefit earthquake hazard assessments in California. The open-source implementation of efficient numerical optimization schemes will also enhance the research activities of other researchers engaged with a similar topic. 2) Career Development. The research activities assisted in the professional development of early-career scientists. 3) Result Communication. We are committed to open science. Once completed, all research products will be made publicly available and via peer-reviewed articles.
Project Participants Rasheed Ajala, Columbia University
Folarin Kolawole, Columbia University
Exemplary Figure Figure 2 | Optimal transport implementation in Seisflows. a, Shear wave velocity sensitivity kernel for the quadratic Wasserstein metric (W2). b, Shear wave velocity sensitivity kernel for the least squares metric (L2). The shear wave speed model is homogeneous, with the difference between the true and initial model being 50 m/s. (Credit: Rasheed Ajala).
Linked Publications

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