Abstract

Distributed acoustic sensing (DAS) delivers real-time observation ofphysical perturbations such as vibrations or strain variations in conventional optical fibers with high sensitivity. The high density of sensing points and large network footprint provided by a single DAS system, along with the availability of a vast optical fiber network already deployed both in land and in oceanic regions, contrast with the high deployment and maintenance cost of conventional instrumentation networks for seismology. This situation has triggered a rapid growth of DAS deployments for seismic monitoring in recent years. Photonic engineers and geophysicists have joined efforts to prove the value of optical fibers as distributed seismometers, which has resulted in a wide panoply of tests demonstrating diverse applicability across the geosciences. For example, DAS has been successfully applied recording local to teleseismic earthquakes, monitoring glacial icequakes, and observing oceanographic phenomena at the sea floor. Most of the realized tests have been performed using commercially available optical fiber interrogators based on phase-sensitive optical time-domain reflectometry. Among them, DAS based on chirped pulse distributed acoustic sensing have provided optimized performance in terms of both range and sensitivity, particularly at low frequencies. In this communication, we provide a comprehensive review of the current situation of DAS for seismology applications, focusing on near surface monitoring, where already deployed optical fibers can be repurposed as sensor networks.

Highlights

  • THE performance of distributed optical fiber sensors has been continuously improving since their conception in terms of resolution, number of monitoring points and sensitivity

  • We provide a comprehensive review of the current situation of distributed acoustic sensor (DAS) for seismology applications, focusing on near surface monitoring, where already deployed optical fibers can be repurposed as sensor networks

  • About 7-8 years ago, one kind of distributed optical fiber sensor based on Rayleigh scattering, known as distributed acoustic sensor (DAS), attracted the attention of geologists and geophysicists for its use in the monitoring of seismic activity

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Summary

INTRODUCTION

THE performance of distributed optical fiber sensors has been continuously improving since their conception in terms of resolution, number of monitoring points and sensitivity. DAS has been successfully employed in active and passive seismic monitoring, in downhole deployments In these studies, dedicated fibers have been installed in boreholes for recording seismic signals at depth, with interesting advantages over traditional downhole receivers, e.g., the higher robustness of the fiber in extreme temperature and pressure over electronic components, the simpler installation procedure and the higher spatial resolution. In near-surface studies, researchers have leveraged the existing network of preexisting optical fibers around the world, resulting in reduced deployment and maintenance cost for seismic monitoring instrumentation relative to conventional technology We sum up the main conclusions that can be extracted from the current status of this line of research

PRINCIPLES OF DISTRIBUTED ACOUSTIC SENSING
TOWARDS COST-EFFICIENT SENSING FIBER NETWORKS
PERFORMANCE OF DAS IN SEISMOLOGY
Denoising algorithms
Compression of DAS data
APPLICATIONS
Earthquake detection
Subsurface characterization and deformation monitoring
Submarine instrumentation
CONCLUSION
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