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Closing the Gap Between Local and Regional Observations of Segmented Ocean Plate Boundaries With a New 25-Year Earthquake Catalog of the European Arctic Seas

Description: 

Oceanic ridges and transform faults comprise nearly 45% of the Earth's plate boundaries. Even though they have lower seismic moment release rates than convergent plate boundaries, these intricately segmented oceanic plate boundaries host a large part of Earth's seismicity. Analyzing how their segmentation is expressed through their seismic behavior has not been commonly possible due to limited observations compared to plate boundaries on land. Even with ocean bottom deployments, a challenge is that there is often no overlap between event catalogs produced routinely from regional networks (typically with M>3.5) or from short local deployments (M<3). To close this gap, we apply a sensitive earthquake detection pipeline to complement a regional catalog over 25 years through template matching. We focus on the 3000 km of oceanic plate boundaries and adjacent areas in the European Arctic (68° - 87°N, 20°W - 40°E). For our initial catalog of 35000 earthquakes, we merge data from local to global observations and consolidate phase picks, hypocenters, and probabilistic location errors with BayesLoc. The waveforms of a well-observed subset with 15500 events form the templates that we correlate against continuous seismograms recorded at up to 300 stations (incl. 8 arrays). We use optimized versions of the software packages RobustRAQN (preparation and quality control), EQcorrscan (template matching) and fmf2 (GPU vendor-agnostic correlation) on a GPU-powered cluster. We set strict thresholds for robust event detections based on correlations and picks at >6 sites and in 3 independent time windows. From >200M initial detections, we filtered out, picked, and relocated >400K earthquakes, revealing oceanic seismicity at an unprecedented scale (25 yrs, Mc<2.5, relative error <2 km). A preliminary analysis shows that earthquake swarms, aftershock sequences, and persistent sites of seismic activity (including repeaters) characterize a complex segmentation of the plate boundary. We relate the activity to the boundary’s tectono-magmatic character which includes (ultra-)slow spreading ridges, volcanic centers, and transform segments.

Session: Deciphering Earthquake Clustering for the Better Understanding of Crustal Deformation Mechanisms [Poster]

Type: Poster

Date: 4/20/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Felix Halpaap

Student Presenter: No

Invited Presentation: 

Authors