Extraction of P Wave From Ambient Seafloor Noise Observed by Distributed Acoustic Sensing

Abstract

Distributed acoustic sensing (DAS) using fiber optic cables is currently a powerful tool for detecting signals of various wave propagations, because the station density along a cable is higher than the typical density of seismic observations using individual seismic sensors. For example, DAS on land is capable of observing signals from regional (Lindsey et al., 2017) and teleseismic earthquakes (Yu et al., 2019) and can estimate shallow S-wave velocity (Vs) structure from ambient noise records (Ajo-Franklin et al., 2019;Dou et al., 2017). P wave is also extracted from ambient noise records acquired by downhole DAS on land (Lellouch et al., 2019). DAS in submarine cables can capture seismic waves from earthquakes (Lior et al., 2021;Lindsey et al., 2019;Sladen et al., 2019) as well as ocean-specific wavefields, including infragravity waves (Williams et al., 2019) and hydroacoustic waves (Matsumoto et al., 2021).As in case of land, ambient noise records observed by DAS have recently been used to estimate the seismic velocity structures beneath submarine cables. Previous studies have estimated the Vs structures within sediment layers in the Japan Trench (Spica et al., 2020) and in the Monterey Bay, California (Cheng et al., 2021). The estimations are based on the retrieval of surface waves, because DAS-based ambient noise records are dominated by surface waves related to microseisms. However, wave-wave interactions from ocean swells indeed excite P

Stacking of Distributed Dynamic Strain Reveals Link Between Seismic Velocity Changes and the 2020 Unrest in Reykjanes

“…This suggests that we can stack adjacent traces in space without introducing bias to the recorded wavefield, in order to increase the SNR of the data. In the context of ambient noise interferometry, spatial stacking of large‐N arrays and DAS has been successfully applied to improve the stability of retrieved Green's functions, for example, in order to reveal body waves in cross‐correlations (e.g., Lin et al., 2013; Nakata et al., 2015; Tonegawa et al., 2022; Wang et al., 2014) and improve surface wave dispersion measurements (e.g., Cheng et al., 2023; Czarny & Zhu, 2022; Jousset et al., 2022; Li et al., 2022; Shragge et al., 2021). It is important to emphasize that we measure velocity changes in the coda of cross‐correlations.…”

“…In multiple studies, it has been shown that DAS resolves structure and dynamics of the sub-surface at unprecedented spatial resolution and at low cost compared to conventional seismometers (e.g., Diaz-Meza et al, 2023;Jousset et al, 2018Jousset et al, , 2022Lindsey et al, 2019;Williams et al, 2019;Zhan, 2019). In the context of ambient noise, DAS has been applied to obtain dispersion curves (e.g., Dou et al, 2017;Luo et al, 2020;Shao et al, 2022;Song et al, 2022;Zhou et al, 2022) and extract body waves through cross-correlation (Tonegawa et al, 2022). Velocity changes caused by ground water fluctuations were tracked along a DAS cable near the Sacramento river in the US (Rodríguez Tribaldos & Ajo-Franklin, 2021).…”

High‐Frequency Tsunamis Excited Near Torishima Island, Japan, Observed by Distributed Acoustic Sensing

“…With a high density of channels along the cable, the distributed acoustic sensing (DAS) technique can monitor the horizontal component of strain along the cable direction, which allows us to investigate the spatial variation of wavefields in detail, including on seafloor telecom cables (Lindsey et al., 2019; Sladen et al., 2019; Williams et al., 2019). This technique has been widely used in marine geophysics for sensing distances of 50–120 km from coastlines to investigate seismological subseafloor structures (Cheng et al., 2021; Fukushima et al., 2022; Lior et al., 2022; Spica et al., 2020; Tonegawa et al., 2022; Viens et al., 2022, 2023), hydroacoustic waves (Matsumoto et al., 2021), Scholte wave generation (Spica et al., 2022), ocean surface gravity waves (Williams et al., 2019), and shallow slow earthquakes (Baba et al., 2023). Ocean DAS records were also uploaded to a repository (Spica et al., 2023) as part of a project that collected DAS data for teleseismic events that occurred in February 2023 (Wuestefeld & Wilks, 2019).…”

Observation of Shallow Slow Earthquakes by Distributed Acoustic Sensing Using Offshore Fiber‐Optic Cable in the Nankai Trough, Southwest Japan

“…Recently, distributed acoustic sensing (DAS) measurement has been widely used for the observations of regular earthquakes (e.g., Lindsey et al., 2017; Shinohara et al., 2022; Zhan, 2019), infragravity waves (Williams et al., 2019), hydroacoustic signals (Matsumoto et al., 2021), and the extraction of P ‐waves from ambient noise (Tonegawa et al., 2022). DAS measurements use an optic fiber cable as a strain or strain rate sensor array.…”