Oceanic detachment faults generate compression in extension

dc.contributor.author Parnell-Turner, Ross
dc.contributor.author Sohn, Robert A.
dc.contributor.author Peirce, Christine
dc.contributor.author Reston, Tim J.
dc.contributor.author MacLeod, Christopher J.
dc.contributor.author Searle, Roger C.
dc.contributor.author Simão, Nuno Mendes
dc.date.accessioned 2017-09-15T15:43:01Z
dc.date.available 2017-09-15T15:43:01Z
dc.date.issued 2017-08
dc.description © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geology 45 (2017): 923-926, doi:10.1130/G39232.1. en_US
dc.description.abstract In extensional geologic systems such as mid-ocean ridges, deformation is typically accommodated by slip on normal faults, where material is pulled apart under tension and stress is released by rupture during earthquakes and magmatic accretion. However, at slowly spreading mid-ocean ridges where the tectonic plates move apart at rates <80 km m.y.–1, these normal faults may roll over to form long-lived, low-angled detachments that exhume mantle rocks and form corrugated domes on the seabed. Here we present the results of a local micro-earthquake study over an active detachment at 13°20′N on the Mid-Atlantic Ridge to show that these features can give rise to reverse-faulting earthquakes in response to plate bending. During a 6 month survey period, we observed a remarkably high rate of seismic activity, with >244,000 events detected along 25 km of the ridge axis, to depths of ∼10 km below seafloor. Surprisingly, the majority of these were reverse-faulting events. Restricted to depths of 3–7 km below seafloor, these reverse events delineate a band of intense compressional seismicity located adjacent to a zone of deeper extensional events. This deformation pattern is consistent with flexural models of plate bending during lithospheric accretion. Our results indicate that the lower portion of the detachment footwall experiences compressive stresses and deforms internally as the fault rolls over to low angles before emerging at the seafloor. These compressive stresses trigger reverse faulting even though the detachment itself is an extensional system. en_US
dc.description.sponsorship This research was funded by Natural Environment Research Council (NERC) grants NE/J02029X/1, NE/ J021741/1, and NE/J022551/1, and by U.S. National Science Foundation grant OCE-1458084. en_US
dc.identifier.citation Geology 45 (2017): 923-926 en_US
dc.identifier.doi 10.1130/G39232.1
dc.identifier.uri https://hdl.handle.net/1912/9231
dc.language.iso en en_US
dc.publisher Geological Society of America en_US
dc.relation.uri https://doi.org/10.1130/G39232.1
dc.rights Attribution 4.0 International *
dc.rights.uri http://creativecommons.org/licenses/by/4.0/ *
dc.title Oceanic detachment faults generate compression in extension en_US
dc.type Article en_US
dspace.entity.type Publication
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