Ocean-Bottom Seismometer Deployment on the Laurentian Fan Seismic Zone: The First Long-Term Test for the Canadian National Facility for Seismological Investigations

Abstract In November 2021, the Canadian National Facility for Seismological Investigations launched its first long-term test of the new Güralp Aquarius broadband ocean-bottom seismometers (OBS). The study targeted the lower Laurentian Fan seismic zone (∼4.5 km water depth), a seismically active zone of oceanic lithosphere downslope from the epicenter of the 1929 Grand Banks earthquake (Ms 7.2) offshore Atlantic Canada. A total of 12 OBS were deployed, of which eight were recovered during an August 2022 recovery cruise, with three months of data suitable for analysis. Because of the absence of Global Positioning System clock synchronization, we performed ambient noise cross-correlation to assess clock drift; seven OBS displayed negligible drift, but one OBS clock had a relative drift of 1.14 s over the three months and was corrected before further analyses. We estimated the orientations of horizontal OBS components using particle-motion analysis of P waves from four teleseismic earthquakes (Mw ≥ 6.8) and their tilt angles using a noise-based transfer-function technique. We then scanned the data for local-to-regional earthquakes using machine learning-based phase picking and automated association tools. Seventeen earthquakes were identified, including two detected by Earthquakes Canada, with estimated local magnitudes up to 2.2 and depths reaching ∼39 km relative to the seafloor. Seismic data also revealed baleen whale calls in the 15–25 Hz range. Using the double-spectrogram method, we detected fin and blue whale vocalizations. Applying a hybrid double-pair double-difference method with cross-correlation delay times, we provide one example 24-hr blue whale track, spanning ∼58 km.