Distributed sensing of microseisms and teleseisms with submarine dark fibers

Abstract

Sparse seismic instrumentation in the oceans limits our understanding of deep Earth dynamics and submarine earthquakes. Distributed acoustic sensing (DAS), an emerging technology that converts optical fiber to seismic sensors, allows us to leverage pre-existing submarine telecommunication cables for seismic monitoring. Here we report observations of microseism, local surface gravity waves, and a teleseismic earthquake along a 4192-sensor ocean-bottom DAS array offshore Belgium. We observe in-situ how opposing groups of ocean surface gravity waves generate double-frequency seismic Scholte waves, as described by the Longuet-Higgins theory of microseism generation. We also extract P- and S-wave phases from the 2018-08-19 Fiji deep earthquake in the 0.01-1 Hz frequency band, though waveform fidelity is low at high frequencies. These results suggest significant potential of DAS in next-generation submarine seismic networks.

Sensing earth and environment dynamics by telecommunication fiber-optic sensors: An urban experiment in Pennsylvania USA

“…This includes geophysical and geotechnical applications: near-surface imaging for planning stable structures, measuring ground motion due to natural sources, monitoring subsidence, identifying major sources of seismic energy, understanding urban hydrological systems, and locating geohazards. The value of DAS has been recognized in inaccessible and harsh environments, enabling offshore ocean observations (Lindsey et al, 2019;Williams et al, 2019), as well as Arctic monitoring as climate change threatens the stability of permafrost under infrastructure (Martin et al, 2016;Ajo-Franklin et al, 2017) and leads to degradation of glaciers (Walter et al, 2020). We anticipate that it will also play an important role in https://doi.org/10.5194/se-2020-103 Preprint.…”

Utilizing Distributed Acoustic Sensing and Ocean Bottom Fiber Optic Cables for Submarine Structural Characterization

“…Observations of ocean surface gravity waves and Scholte (P-SV solid-liquid interface) waves from marine DAS records have been recently reported by Sladen et al [41], Williams et al [42], Lindsey et al [34], Spica et al [35]. However, the raw strain-rate records of DAS ( Fig.2) are complicated by the superposition of a variety of coherent signals dominated by different frequency components, as well as incoherent and optical noise effects, e.g., temperature drift, interrogator unit shake, coupling issues.…”

Fiber Optic Distributed Strain Sensing for Seismic Applications

“…More and more applications in various fields of Earth Sciences are emerging, e.g., measurements in marine environment, taking advantage of the network of optical cables (e.g., Lindsey et al 2019;Marra et al 2018;Sladen et al 2019;Williams et al 2019;Jousset 2019). First measurements were also performed on active volcanoes and cities build on the flancs of active volcanoes (Jousset et al 2019) using infrastructure of temporary or permanent monitoring networks (Contrafatto et al 2019).…”