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Abstract We present a real-data test for offshore earthquake early warning (EEW) with distributed acoustic sensing (DAS) by transforming submarine fiber-optic cable into a dense seismic array. First, we constrain earthquake locations using the arrival-time information recorded by the DAS array. Second, with site effects along the cable calibrated using an independent earthquake, we estimate earthquake magnitudes directly from strain rate amplitudes by applying a scaling relation transferred from onshore DAS arrays. Our results indicate that using this single 50 km offshore DAS array can offer ∼3 s improvement in the alert time of EEW compared to onshore seismic stations. Furthermore, we simulate and demonstrate that multiple DAS arrays extending toward the trench placed along the coast can uniformly improve alert times along a subduction zone by more than 5 s.
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This content will become publicly available on January 30, 2026
Leveraging Submarine DAS Arrays for Offshore Earthquake Early Warning: A Case Study in Monterey Bay, California
ABSTRACT Detecting offshore earthquakes in real time is challenging for traditional land-based seismic networks due to insufficient station coverage. Application of distributed acoustic sensing (DAS) to submarine cables has the potential to extend the reach of seismic networks and thereby improve real-time earthquake detection and earthquake early warning (EEW). We present a complete workflow of a modified point-source EEW algorithm, which includes a machine-learning-based model for P- and S-wave phase picking, a grid-search location method, and a locally calibrated empirical magnitude estimation equation. Examples are shown with offshore earthquakes from the SeaFOAM DAS project using a 52-km-long submarine cable in Monterey Bay, California, demonstrating the robustness of the proposed workflow. When comparing to the current onshore network, we can expect up to 6 s additional warning time for earthquakes in the offshore San Gregorio fault zone, representing a substantial improvement to the existing ShakeAlert EEW system.
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- Award ID(s):
- 2023301
- PAR ID:
- 10616905
- Editor(s):
- Mai, P M
- Publisher / Repository:
- Bulletine of the Seismological Society of America
- Date Published:
- Journal Name:
- Bulletin of the Seismological Society of America
- Volume:
- 115
- Issue:
- 2
- ISSN:
- 0037-1106
- Page Range / eLocation ID:
- 516 to 532
- Subject(s) / Keyword(s):
- DAS Earthquakes Earthquake Early Warning
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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