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Seismicity trends and detachment fault structure at 13N, Mid-Atlantic Ridge

Parnell-Turner, Ross, Sohn, Robert, Peirce, Christine, Reston, Tim, MacLeod, Christopher, Searle, Roger and Simao, Nuno 2020. Seismicity trends and detachment fault structure at 13N, Mid-Atlantic Ridge. Geology 10.1130/G48420.1
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At slow-spreading ridges, plate separation is commonly partly accommodated by slip on long-lived detachment faults, exposing upper mantle and lower crustal rocks on the seafloor. However, the mechanics of this process, the subsurface structure, and the interaction of these faults remain largely unknown. We report the results of a network of 56 ocean-bottom seismographs (OBSs), deployed in 2016 at the Mid-Atlantic Ridge near 13°N, that provided dense spatial coverage of two adjacent detachment faults and the intervening ridge axis. Although both detachments exhibited high levels of seismicity, they are separated by an ~8-km-wide aseismic zone, indicating that they are mechanically decoupled. A linear band of seismic activity, possibly indicating magmatism, crosscuts the 13°30′N domed detachment surface, confirming previous evidence for fault abandonment. Farther south, where the 2016 OBS network spatially overlapped with a similar survey done in 2014, significant changes in the patterns of seismicity between these surveys are observed. These changes suggest that oceanic detachments undergo previously unobserved cycles of stress accumulation and release as plate spreading is accommodated.

Item Type: Article
Date Type: Published Online
Status: In Press
Schools: Earth and Ocean Sciences
Publisher: Geological Society of America
ISSN: 0091-7613
Date of First Compliant Deposit: 8 October 2020
Date of Acceptance: 22 September 2020
Last Modified: 24 Nov 2020 18:01

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