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Intermediate-depth earthquakes facilitated by eclogitization-related stresses

Geology

By:
, , , , , and
DOI: 10.1130/G33796.1

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Abstract

Eclogitization of the basaltic and gabbroic layer in the oceanic crust involves a volume reduction of 10%–15%. One consequence of the negative volume change is the formation of a paired stress field as a result of strain compatibility across the reaction front. Here we use waveform analysis of a tiny seismic cluster in the lower crust of the downgoing Pacific plate and reveal new evidence in favor of this mechanism: tensional earthquakes lying 1 km above compressional earthquakes, and earthquakes with highly similar waveforms lying on well-defined planes with complementary rupture areas. The tensional stress is interpreted to be caused by the dimensional mismatch between crust transformed to eclogite and underlying untransformed crust, and the earthquakes are probably facilitated by reactivation of fossil faults extant in the subducting plate. These observations provide seismic evidence for the role of volume change–related stresses and, possibly, fluid-related embrittlement as viable processes for nucleating earthquakes in downgoing oceanic lithosphere.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Intermediate-depth earthquakes facilitated by eclogitization-related stresses
Series title:
Geology
DOI:
10.1130/G33796.1
Volume
41
Issue:
6
Year Published:
2013
Language:
English
Publisher:
Geological Society of America
Publisher location:
Boulder, CO
Description:
4 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Geology
First page:
659
Last page:
662