Improved Seismic Monitoring with OBS Deployment in the Arctic: A Pilot Study from Offshore Western Svalbard

Zeinab Jeddi,Sara Rezaei,Steven J Gibbons,Lars Ottemöller,Mathilde B Sørensen,Trine Dahl-Jensen,Marte L Strømme,Peter H Voss

doi:10.1785/0220200471

Abstract

AbstractThe mid-ocean ridge system is the main source of earthquakes within the Arctic region. The earthquakes are recorded on the permanent land-based stations in the region, although, smaller earthquakes remain undetected. In this study, we make use of three Ocean Bottom Seismographs (OBSs) that were deployed offshore western Svalbard, along the spreading ridges. The OBS arrival times were used to relocate the regional seismicity, using a Bayesian approach, which resulted in a significant improvement with tighter clustering around the spreading ridge. We also extended the regional magnitude scales for the northern Atlantic region for OBSs, by computing site correction terms. Besides location and magnitude improvement, the OBS network was able to detect hundreds of earthquakes, mostly with magnitude below Mw 3, including a swarm activity at the Molloy Deep. Our offshore observations provide further evidence of a low-velocity anomaly offshore Svalbard, at the northern tip of Knipovich ridge that was previously seen in full-waveform inversion. We conclude that even a single permanent OBS near the ridge would make a significant difference to earthquake catalogs and their interpretation.

Highlights

Mid-ocean ridges play an important role in plate tectonics as that is where new oceanic lithosphere is created
Temporary Ocean Bottom Seismograph (OBS) deployments have become feasible in remote areas such as mid-ocean ridges, in order to monitor smaller earthquakes that are not detected by land-based seismic networks e.g., ETMC network (Eguchi et al, 1998 ), CYC-NET project (Bohnhoff et al, 2004), TYDE experiment (Sgroi et al, 2009), and EarthScope-Oceans (Simons et al, 2019)
Earthquakes along the Arctic mid-ocean ridge (AMOR) clearly define the ridge as a divergent plate boundary

Summary

Introduction

Mid-ocean ridges play an important role in plate tectonics as that is where new oceanic lithosphere is created. Earthquake monitoring experiments such as the INTAROS OBSs deployment along the AMOR can in addition contribute considerably to improve seismic catalogs at the regional scale.

Results

Conclusion