National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 2022

Multi-stage evolution of the Lost City hydrothermal vent fluids

Aquino, K.A., G.L. Früh-Green, J. Rickli, S.M. Bernasconi, S.Q. Lang, M.D. Lilley, and D.A. Butterfield

Geochim. Cosmochim. Acta, 332, 239-262, doi: 10.1016/j.gca.2022.06.027, View online, open access - link to external site (publisher) (2022)

Seismicity along mid-ocean ridges and oceanic transform faults provides insights into the processes of crustal accretion and strike-slip deformation. In the equatorial Atlantic ocean, the slow-spreading Mid-Atlantic Ridge is offset by some of the longest-offset transform faults on Earth, which remain relatively poorly understood due to its remote location far from land-based teleseismic receivers. A catalog of T-phase events detected by an array of 10 autonomous hydrophones deployed between 2011 and 2015, extending from 20°N to 10°S is presented. The final catalog of 6,843 events has a magnitude of completeness of 3.3, compared to 4.4 for the International Seismic Center teleseismic catalog covering the same region, and allows investigation of the dual processes of crustal accretion and transform fault slip. The seismicity rate observed at asymmetric spreading segments (those hosting detachment faults) is significantly higher than that of symmetric spreading centers, and 74% of known hydrothermal vents along the equatorial Mid-Atlantic Ridge occur on asymmetric spreading segments. Aseismic patches are present on nearly all equatorial Atlantic transform faults, including on the Romanche transform where regional rotation and transpression could explain both bathymetric uplift and reduction in seismic activity. The observed patterns in seismicity provide insight into the thermal and mechanical structure of the ridge axis and associated transform faults, and potentially provide a method for investigating the distribution of hydrothermal vent systems.

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