SCEC Award Number 25189 View PDF
Proposal Category Individual Research Project (Single Investigator / Institution)
Proposal Title High-resolution imaging and earthquake locations of the Mendocino Triple Junction through Eikonal tomography and relocation by combining seismic stations and distributed acoustic sensing arrays
Investigator(s)
Name Organization
Ettore Biondi Stanford University
SCEC Milestones A1-1, C1-1, A3-2 SCEC Groups Seismology, CEM, GM
Report Due Date 03/15/2026 Date Report Submitted 03/12/2026
Project Abstract
 This project evaluates the potential of distributed acoustic sensing (DAS) to enhance seismic imaging and earthquake monitoring near the Mendocino Triple Junction (MTJ) by integrating DAS observations with the Northern California Seismic Network (NCSN). To assess the resolving power of the combined network, we performed synthetic resolution tests using an adjoint-state Eikonal tomography framework with checkerboard velocity anomalies of different spatial scales. The experiments compared three scenarios: DAS-only data, seismic stations only, and a joint inversion combining both datasets using a background model derived from the SCEC Community Velocity Model.

Results show that DAS alone has limited regional imaging capability due to its restricted aperture, but significantly improves the resolution of smaller-scale velocity anomalies when combined with the regional seismic network. In addition, cross-correlation analysis of DAS waveforms demonstrates that the data can provide stable differential travel-time measurements suitable for earthquake relocation and source studies. These results highlight the potential of integrating DAS with existing seismic networks to improve high-resolution imaging in tectonically complex regions.
SCEC Community Models Used Community Velocity Model (CVM)
Usage Description The SCEC Community Velocity Model (CVM) was used as the background velocity model for the synthetic resolution tests performed in this study. The CVM provided the initial seismic velocity structure used to generate synthetic travel times for checkerboard experiments and sensitivity analyses within the Eikonal tomography framework. Using the CVM ensured that the synthetic tests were conducted within a realistic representation of crustal structure in Northern California. This allowed us to evaluate how the combination of distributed acoustic sensing (DAS) data and regional seismic stations improves tomographic resolution relative to conventional station-only networks.
Intellectual Merit This project advances SCEC objectives by evaluating how distributed acoustic sensing (DAS) can enhance earthquake imaging and monitoring capabilities in tectonically complex regions such as the Mendocino Triple Junction. By integrating DAS observations with conventional seismic stations, we demonstrated improvements in the resolution of velocity anomalies and the potential for high-precision differential travel-time measurements using DAS waveforms. The study explores the use of secondary seismic phases within an Eikonal tomography framework, introducing new approaches for imaging structures related to fluid accumulation and fault processes. These developments contribute to SCEC broader goal of improving subsurface imaging and understanding fault zones.
Broader Impacts The project contributed to training and education by involving a PhD student who gained experience in seismic imaging, distributed acoustic sensing (DAS) analysis, and tomographic methods. Through this work, the student became familiar with the role of SCEC in advancing collaborative earthquake science and the broader seismological research community. The project also contributes to research infrastructure by exploring the integration of dense DAS arrays with existing seismic networks, which can enhance earthquake monitoring capabilities. These developments support improved observational tools for earthquake studies and may ultimately contribute to better understanding of seismic hazards in tectonically active regions.
Project Participants The project was conducted by Ettore Biondi (Stanford University) together with a PhD student in his research group who contributed to the analysis and development of the tomography workflow. The project included collaboration with the United States Geological Survey (USGS), particularly with James Atterholt, who was involved in the DAS deployment and provided access to the fiber-optic data used in this study. This collaboration enabled the integration of DAS observations with regional seismic network data and supported the evaluation of DAS capabilities for earthquake imaging and monitoring in the Mendocino Triple Junction region.
Exemplary Figure Figure 2: Checkerboard resolution test with 5-km-scale velocity anomalies. Columns show (from left to right) the input model, the inversion using DAS-only travel times, the inversion using NCSN stations only, and the joint DAS + station inversion.
Linked Publications

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