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

Ingo Grevemeyer, Nicholas W. Hayman, Dietrich Lange, Christine Peirce, Cord Papenberg, Harm J. A. Van Avendonk, Florian Schmid, Laura Gomez de la Pena and Anke Dannowski
Constraining the maximum depth of brittle deformation at slow- and ultraslow-spreading ridges using microseismicity
Geology (Boulder) (November 2019) 47 (11): 1069-1073

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 approximately 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.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 47
Serial Issue: 11
Title: Constraining the maximum depth of brittle deformation at slow- and ultraslow-spreading ridges using microseismicity
Affiliation: GEOMAR Helmholtz Centre of Ocean Research, Kiel, Germany
Pages: 1069-1073
Published: 201911
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 28
Accession Number: 2019-095249
Categories: Solid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Respository item 2019371
Illustration Description: illus. incl. geol. sketch map
N17°45'00" - N18°45'00", W82°00'00" - W81°25'00"
Secondary Affiliation: University of Texas-Austin, USA, United StatesUniversity of Durham, GBR, United Kingdom
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201923
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