none 10.1190/INT-2021-0195.1 Society of Exploration Geophysicists Society of Exploration Geophysicists 186 132491179 226307 2025120913563402400 10.1190 2025-12-09T18:56:44Z 2021-11-28T09:52:41Z 5 Interpretation 2324-8858 2324-8866 02 01 2022 10 1 Anne M. Tréhu Oregon State University 1 , College of Earth, Ocean, and Atmospheric Sciences, Corvallis, Oregon 97331-5503, USA. E-mail: anne.trehu@oregonstate.edu . Jeffrey W. Beeson Cooperative Institute for Marine Ecosystem and Resources Studies — Oregon State University 2 , and NOAA PMEL Earth Ocean Interactions Program, Newport, Oregon 97365, USA. E-mail: jeff.beeson@noaa.gov (corresponding author); susan.merle@noaa.gov . http://orcid.org/0000-0002-7396-237X Susan G. Merle Cooperative Institute for Marine Ecosystem and Resources Studies — Oregon State University 2 , and NOAA PMEL Earth Ocean Interactions Program, Newport, Oregon 97365, USA. E-mail: jeff.beeson@noaa.gov (corresponding author); susan.merle@noaa.gov . Abstract Acoustic echosounding systems are increasingly used to image water-column backscatter in addition to mapping the seafloor. We have imaged an acoustic flare generated by methane bubbles emanating from a vent sourced at 1840 m water depth offshore northern California using a shipboard Kongsberg EM122. Data include five transits over the flare and approximately 11 h of continuous observation when the ship held station. Shipboard observations showed a strong flare splitting into multiple smaller, intermittent flares at a water depth of 800–1200 m and pronounced temporal variability. We introduce a new approach to processing the data in which we correct the backscatter data for ship motion and bin the data into voxels with dimensions of 20 m in X and Y and 40 m in Z for a transit over the flare and into vertical slices with dimensions of 15 m in X and Z and 4 min in time when the ship was stationary. The processed data indicate that the signal is dominated by bubbles emanating from a source region with a diameter of approximately 40 m located on the southern edge of what is likely a ring of sources with a diameter of approximately 600 m. When the ship was stationary, we were able to track an individual pulse rising at a rate of 8–10 m/min. Our results illustrate the limitations of monitoring temporal variation in gas flux using multibeam echosounders because of the trade-off between imaging the entire flare by averaging over tens of minutes to hours and observing a slice through the flare to capture short-lived pulses of gas expulsion. Nevertheless, because echosounders are widely available, they can continue to provide valuable data on the spatial and temporal distribution of gas emissions on continental margins that can be used to frame hypotheses and plan more comprehensive follow-up experiments. 02 01 2022 01 26 2022 SB93 SB106 http://www.niso.org/schemas/ali/1.0/ 1 10.1190/crossmark-policy library.seg.org true 2021-10-02 2021-11-05 2022-01-26 http://creativecommons.org/licenses/by/4.0/ 10.1190/INT-2021-0195.1 https://pubs.geoscienceworld.org/interpretation/article/10/1/SB93/611095/A-new-approach-to-processing-and-imaging-multibeam https://pubs.geoscienceworld.org/seg/interpretation/article-pdf/10/1/SB93/5555738/int-2021-0195.1.pdf https://pubs.geoscienceworld.org/seg/interpretation/article-pdf/10/1/SB93/5555738/int-2021-0195.1.pdf https://pubs.geoscienceworld.org/interpretation/article/10/1/sb93/611095/a-new-approach-to-processing-and-imaging-multibeam 0278-7407 Tectonics Adam 23 2004 10.1029/2002TC001475 Upward delamination of Cascadia Basin sediment infill with landward frontal accretion thrusting caused by rapid glacial age material flux AT26-02 Science Party, 2013, Cruise report Cascadia initiative: Year 3, Leg 3, 25 June 2013–9 July 2013, https://www.rvdata.us/search/cruise/AT26-02, accessed 19 December 2021. 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