Passive acoustic monitoring of a major seismic event at the Main Endeavour Hydrothermal Vent Field

A major seismic event occurred in the region of the Main Endeavour Hydrothermal Vent Field (MEF) on March 5–6, 2024. During this 48-h period, a 4.1 magnitude event and up to 200 earthquakes per hour were recorded by Ocean Networks Canada’s (ONC) cabled North-East Pacific Time-series Undersea Networked Experiments (NEPTUNE) observatory. Low frequency waterborne acoustic signals associated with the earthquakes were detected by a four-element “box-type” hydrophone array located near multiple black smoker hydrothermal vents, with two of these elements being active during the event. Broadband signals up to 10 kHz were also measured by the hydrophones. Power spectral densities before, during, and after the seismic event show increases up to 50 dB relative to ambient levels below 100 Hz and increases up to 20 dB between 100 Hz and 10 kHz during the event. Power spectral densities between 100 Hz and 10 kHz remain elevated by approximately 5 dB more than one week following the seismic event. Power spectral density and complex coherence measurements, as well as cross-correlation with other sensors at MEF, suggest that these broadband signals may be associated with changes to the hydrothermal vent field resulting from the increased seismicity in this region.