Monitoring megathrust faults with abyssal distributed acoustic sensing

Informations projet

ABYSS

N° de convention de subvention: 101041092

DOI

10.3030/101041092

Date de signature de la CE 5 Mai 2022

Date de début 1 Octobre 2022

Date de fin 30 Septembre 2027

Financé au titre de

• European Research Council (ERC)

Coût total

€ 2 134 970,00

Contribution de l’UE

€ 2 134 970,00

Coordonné par

OBSERVATOIRE DE LA COTE D'AZUR (OCA)
France

Periodic Reporting for period 1 - ABYSS (Monitoring megathrust faults with abyssal distributed acoustic sensing)

Période du rapport: 2022-10-01 au 2025-03-31

Résumé du contexte et des objectifs généraux du projet

Earthquakes have caused more than half a million of fatalities in the past 20 years. A large fraction of this death toll arises from the current lack of systematic predictive signals. While some theories suggest earthquakes are inherently unpredictable, evidence from laboratory and numerical experiments indicates they may be preceded by a preparatory phase. However, observations of this phase remain incomplete, mainly because extensive sensor networks cannot be deployed on the ocean floor near earthquake nucleation zones—particularly for large earthquakes most likely to produce precursors detectable at the surface.

The ABYSS project aims to address this gap by leveraging offshore fiber optic telecommunication cables along the Chilean subduction zone. By converting several ~100 km segments of these cables into a dense ocean-bottom seismic observatory, the project will generate unique data capable of detecting weak earthquakes and subtle changes in crustal properties with greater sensitivity, beyond the capabilities of onshore seismic networks. This transformative technology, combined with real-time data processing workflows, will enhance Chile’s early warning system by improving the timeliness and accuracy of earthquake warnings.

The project therefore has three key scientific goals: (1) to enhance sensitivity to small seismic events, particularly near the nucleation zones of large earthquakes; (2) to achieve high-resolution imaging of crustal structures and monitor changes over time; and (3) to develop a prototype fiber optic-based early warning system, paving the way for reliable earthquake detection and response mechanisms. The expected outcomes of this project will have a transformative impact on earthquake science as well as on the reduction of societal vulnerability to natural hazards.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

The ABYSS project explores the use of offshore telecom fiber cables as underwater seismological observatories. Over two years, it implemented a system for real-time earthquake monitoring in central Chile, using 30,000 sensing points along 450 km of fiber optic cables. This approach has improved sensitivity to offshore seismic activity and supported earthquake monitoring with advanced data streaming technologies.

A central development of the project is an automated seismic monitoring platform for central Chile. This platform processes real-time data to detect, locate, and characterize earthquakes, forming the basis for a future earthquake early warning system. Each day, hundreds of seismic events detected and characterized by the ABYSS network are displayed on the dedicated website. The project has also created specialized workflows for DAS data, powered by the open-source Python library XDAS, which we developed to enable efficient DAS data management.

The project has also tested the potential of distributed acoustic sensing (DAS) technology for early warning systems. DAS offers high spatial resolution offshore, allowing faster detection and magnitude estimation compared to traditional onshore networks. While challenges such as signal saturation for large earthquakes remain, scaling relationships and magnitude estimation methods are being developed to address these limitations. These efforts contribute to improving earthquake monitoring and early warning capabilities.

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

Efforts have focused on building an offshore seismological observatory in central Chile using underwater telecom cables, enabling the observation of seismicity and offshore processes where our knowledge has been limited due to the lack of instrumentation. Building such infrastructure represents an important breakthrough, and its development is progressing well.

Thanks to this infrastructure and unprecedented spatial resolution, we have already highlighted the spatial variation in sediment coverage—a major feature that profoundly impacts seismic waveforms—which has been observed and characterized for the first time. With a better understanding of near-surface effects on seismic signals, we can now correct for these effects and obtain a clearer view of the earthquake source signatures.
Over the past year, continuous recordings on three cables, each spanning 150 km, have captured several local events with magnitudes greater than 6. These measurements have improved our understanding of the method's limitations for early warning systems and identified potential strategies to mitigate these challenges.

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