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Surface Gravity Wave Interferometry and Ocean Current Monitoring With Ocean‐Bottom DAS

Williams, Ethan F. and Zhan, Zhongwen and Martins, Hugo F. and Fernández-Ruiz, María R. and Martín-López, Sonia and González-Herráez, Miguel and Callies, Jörn (2022) Surface Gravity Wave Interferometry and Ocean Current Monitoring With Ocean‐Bottom DAS. Journal of Geophysical Research. Oceans, 127 (5). Art. No. e2021JC018375. ISSN 2169-9275. doi:10.1029/2021jc018375.

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The cross-correlation of a diffuse or random wavefield at two points has been demonstrated to recover an empirical estimate of the Green's function under a wide variety of source conditions. Over the past two decades, the practical development of this principle, termed ambient noise interferometry, has revolutionized the fields of seismology and acoustics. Yet, because of the spatial sparsity of conventional water column and seafloor instrumentation, such array-based processing approaches have not been widely utilized in oceanography. Ocean-bottom distributed acoustic sensing (OBDAS) repurposes pre-existing optical fibers laid in seafloor cables as dense arrays of broadband strain sensors, which observe both seismic waves and ocean waves. The thousands of sensors in an OBDAS array make ambient noise interferometry of ocean waves straightforward for the first time. Here, we demonstrate the application of ambient noise interferometry to surface gravity waves observed on an OBDAS array near the Strait of Gibraltar. We focus particularly on a 3-km segment of the array on the continental shelf, containing 300 channels at 10-m spacing. By cross-correlating the raw strain records, we compute empirical ocean surface gravity wave Green's functions for each pair of stations. We first apply beamforming to measure the time-averaged dispersion relation along the cable. Then, we exploit the non-reciprocity of waves propagating in a flow to recover the depth-averaged current velocity as a function of time using a waveform stretching method. The result is a spatially continuous matrix of current velocity measurements with resolution <100 m and <1 hr.

Item Type:Article
Related URLs:
URLURL TypeDescription ItemCode
Williams, Ethan F.0000-0002-7917-4104
Zhan, Zhongwen0000-0002-5586-2607
Martins, Hugo F.0000-0003-3927-8125
Martín-López, Sonia0000-0001-5203-6206
González-Herráez, Miguel0000-0003-2555-2971
Callies, Jörn0000-0002-6815-1230
Additional Information:© 2022 American Geophysical Union. Issue Online: 08 May 2022; Version of Record online: 08 May 2022; Accepted manuscript online: 28 April 2022; Manuscript accepted: 27 April 2022; Manuscript revised: 30 March 2022; Manuscript received: 21 December 2021. We thank Red Eléctrica de España for access to their cable and Aragon Photonics for providing the interrogator unit. E. F. Williams was supported by an NSF Graduate Research Fellowship. Z. Zhan acknowledges support from the Moore Foundation and NSF under CAREER Award 1848166. M. R. Fernández-Ruiz acknowledges support from the Spanish MICINN under contract IJC2018-035684-I. M. González-Herráez acknowledges support from projects RTI2018-097957-B-C31 and RTI2018-097957-B-C33 funded by the Spanish Ministry of Science and Innovation, project SINFOTON2-CM: P2018/NMT-4326 funded by Comunidad de Madrid and Fondo Europeo de Desarrollo Regional (FEDER) Program, and project PLEC2021-007875 funded by the Spanish Ministry of Science and Innovation MCIN/AEI/10.13039/501100011033 and by the European Union NextGenerationEU/PRTR program. The authors declare no conflicts of interest relevant to this study. Data Availability Statement. The data used in this paper are proprietary and not available for public release. However, the code necessary to reproduce the methods of this paper is available at, using the public data set of Williams et al. (2019) (
Group:Seismological Laboratory
Funding AgencyGrant Number
NSF Graduate Research FellowshipUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Ministerio de Ciencia e Innovación (MCINN)IJC2018-035684-I
Ministerio de Economía, Industria y Competitividad (MINECO)RTI2018-097957-B-C31
Ministerio de Ciencia e Innovación (MCINN)RTI2018-097957-B-C33
Comunidad de MadridP2018/NMT-4326
European UnionPLEC2021-007875
Ministerio de Economía, Industria y Competitividad (MINECO)10.13039/501100011033
Subject Keywords:distributed acoustic sensing; ocean currents; ocean surface gravity waves; ambient noise interferometry
Issue or Number:5
Record Number:CaltechAUTHORS:20220609-879699300
Persistent URL:
Official Citation:Williams, E. F., Zhan, Z., Martins, H. F., Fernández-Ruiz, M. R., Martín-López, S., González-Herráez, M., & Callies, J. (2022). Surface gravity wave interferometry and ocean current monitoring with ocean-bottom DAS. Journal of Geophysical Research: Oceans, 127, e2021JC018375.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115106
Deposited By: Tony Diaz
Deposited On:13 Jun 2022 17:38
Last Modified:13 Jun 2022 17:38

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