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DAS Beyond Repeaters: Multi-span Monitoring Using Submarine Cables in the Pacific Ocean

Distributed acoustic sensing (DAS) transforms seafloor fiber-optic cables into dense arrays of strain sensors. Until recently, observations have been limited by optical repeaters to the first cable span, typically <100 km offshore. Advancements by Nokia Bell Labs, which leverage the high-loss loopback couplers within repeaters, now allow for multi-span recordings of strain across the entirety of transoceanic cables. This technique has been used to successfully record the 2025 M8.8 Kamchatka earthquake and tsunami at teleseismic range with a spatial resolution of ~100 m across 4400 km of seafloor fiber. In November 2025, the multi-span system was deployed for 3 months on both cables of the Ocean Observatories Initiative Regional Cabled Array (OOI RCA) offshore Oregon, spanning the forearc of the Cascadia subduction zone and extending ~500 km to Axial Seamount. Simultaneously, the first span of the south cable was interrogated with a multiplexed conventional DAS unit and data continued to stream from cabled seismometers, hydrophones, and other oceanographic instruments on the OOI RCA. During the initial testing, a regional earthquake was successfully recorded by the multi-span system. The dataset will be publicly available following documentation and data quality checks. We seek to characterize the noise floor and sensitivity of this technique in comparison to co-located seismometers and conventional DAS interrogators, and in turn, explore its potential for applications including routine earthquake monitoring, earthquake early warning, and oceanographic and marine mammal observation. We will report preliminary results from the experiment including the overall background noise characteristics and the nature and consistency of seismic, oceanographic and acoustic signals between the data types. These results represent an important step toward detailing the broader value of this technique for the seismic community and beyond.

Session: Fiber-Optic Sensing Applications in Seismology and Environmental Science - V

Type: Oral

Room: Ballroom E

Date: 4/17/2026

Presentation Time: 05:30 PM (local time)

Presenting Author: Zoe Krauss

Student Presenter: No

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