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Constraining the maximum depth of brittle deformation at slow- and ultraslow-spreading ridges using microseismicity

Grevemeyer, I.; Hayman, N.W.; Lange, D.; Peirce, C.; Papenberg, C.; Van Avendonk, H.J.A.; Schmid, F.; Gomez de La Pena, L.; Dannowski, A.

Constraining the maximum depth of brittle deformation at slow- and ultraslow-spreading ridges using microseismicity Thumbnail


Authors

I. Grevemeyer

N.W. Hayman

D. Lange

C. Papenberg

H.J.A. Van Avendonk

F. Schmid

L. Gomez de La Pena

A. Dannowski



Abstract

The depth of earthquakes along mid-ocean ridges is restricted by the relatively thin brittle lithosphere that overlies a hot, upwelling mantle. With decreasing spreading rate, earthquakes may occur deeper in the lithosphere, accommodating strain within a thicker brittle layer. New data from the ultraslow-spreading Mid-Cayman Spreading Center (MCSC) in the Caribbean Sea illustrate that earthquakes occur to 10 km depth below seafloor and, hence, occur deeper than along most other slow-spreading ridges. The MCSC spreads at 15 mm/yr full rate, while a similarly well-studied obliquely opening portion of the Southwest Indian Ridge (SWIR) spreads at an even slower rate of ∼8 mm/yr if the obliquity of spreading is considered. The SWIR has previously been proposed to have earthquakes occurring as deep as 32 km, but no shallower than 5 km. These characteristics have been attributed to the combined effect of stable deformation of serpentinized mantle and an extremely deep thermal boundary layer. In the context of our MCSC results, we reanalyze the SWIR data and find a maximum depth of seismicity of 17 km, consistent with compilations of spreading-rate dependence derived from slow- and ultraslow-spreading ridges. Together, the new MCSC data and SWIR reanalysis presented here support the hypothesis that depth-seismicity relationships at mid-ocean ridges are a function of their thermal-mechanical structure as reflected in their spreading rate.

Citation

Grevemeyer, I., Hayman, N., Lange, D., Peirce, C., Papenberg, C., Van Avendonk, H., …Dannowski, A. (2019). Constraining the maximum depth of brittle deformation at slow- and ultraslow-spreading ridges using microseismicity. Geology, 47(11), 1069-1073. https://doi.org/10.1130/g46577.1

Journal Article Type Article
Acceptance Date Aug 22, 2019
Online Publication Date Sep 23, 2019
Publication Date 2019
Deposit Date Aug 5, 2019
Publicly Available Date Mar 29, 2024
Journal Geology
Print ISSN 0091-7613
Electronic ISSN 1943-2682
Publisher Geological Society of America
Peer Reviewed Peer Reviewed
Volume 47
Issue 11
Pages 1069-1073
DOI https://doi.org/10.1130/g46577.1

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