Origin and Periodic Behavior of Short Duration Signals Recorded by Seismometers at Vestnesa Ridge, an Active Seepage Site on the West-Svalbard Continental Margin

P Domel,H Ramachandran,V Schlindwein,S Singhroha,S Bünz,A Plaza-Faverola

doi:10.3389/feart.2022.831526

Abstract

Short duration events (SDEs) are reported worldwide from ocean-bottom seismometers (OBSs). Due to their high frequency (4–30 Hz) and short duration, they are commonly attributed to aseismic sources, such as fluid migration related processes from cold seeps, biological signals, or noise. We present the results of a passive seismic experiment that deployed an OBS network for 10-month (October 2015–July 2016) at an active seepage site on Vestnesa Ridge, West Svalbard continental margin. We characterize SDEs and their temporal occurrence using the conventional short-time-average over long-time-average approach. Signal periodograms show that SDEs have periodic patterns related to solar and lunar cycles. A monthly correlation between SDE occurrences and modelled tides for the area indicates that tides have a partial control on SDEs recorded over 10 months. The numbers of SDEs increase close to the tidal minima and maxima, although a correlation with tidal highs appears more robust. Large bursts of SDEs are separated by interim quiet cycles. In contrast, the periodicity analysis of tremors shows a different pattern, likely caused by the effect of tidally controlled underwater currents on the instrumentation. We suggest that SDEs at Vestnesa Ridge may be related to the dynamics of the methane seepage system which is characterized by a complex interaction between migration of deep sourced fluids, gas hydrate formation and seafloor gas advection through cracks. Our observation from this investigated area offshore west-Svalbard, is in line with the documentation of SDEs from other continental margins, where micro-seismicity and gas release into the water column are seemingly connected.

Highlights

Ocean-bottom seismometers (OBSs) are usually deployed in marine settings to investigate local seismicity of an area by monitoring earthquakes (e.g., Grevemeyer et al, 2015; Meier et al, 2021) or long-duration tremors (e.g., Monigle et al, 2009; Hsu et al, 2013; Franek et al, 2014).In addition to earthquakes and tremors, ocean bottom seismometers (OBS) often record signals commonly referred to as short duration events (SDEs) (e.g., Díaz et al, 2007; Tary et al, 2012; Franek et al, 2017)
We report on SDE occurrences in 10-month-long OBS recordings from an actively seeping pockmark on Vestnesa Ridge, a sedimentary ridge located offshore west-Svalbard
We observe that the number of SDE occurrences varies with time along the records and these variations are not regular

Summary

Introduction

Ocean-bottom seismometers (OBSs) are usually deployed in marine settings to investigate local seismicity of an area by monitoring earthquakes (e.g., Grevemeyer et al, 2015; Meier et al, 2021) or long-duration tremors (e.g., Monigle et al, 2009; Hsu et al, 2013; Franek et al, 2014). In addition to earthquakes and tremors, OBSs often record signals commonly referred to as short duration events (SDEs) (e.g., Díaz et al, 2007; Tary et al, 2012; Franek et al, 2017). SDEs are characterized by a single pulse of a short (usually

Results

Discussion

Conclusion