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Intermediate-depth earthquake generation and shear zone formation caused by grain size reduction and shear heating

M. Thielmann, A. Rozel, B. J. P. Kaus and Y. Ricard
Intermediate-depth earthquake generation and shear zone formation caused by grain size reduction and shear heating
Geology (Boulder) (July 2015) 43 (9): 791-794

Abstract

The underlying physics of intermediate-depth earthquakes have been an enigmatic topic; several studies support either thermal runaway or dehydration reactions as viable mechanisms for their generation. Here we present fully coupled thermomechanical models that investigate the impact of grain size evolution and energy feedbacks on shear zone and pseudotachylite formation. Our results indicate that grain size reduction weakens the rock prior to thermal runaway and significantly decreases the critical stress needed for thermal runaway, making it more likely to result in intermediate-depth earthquakes at shallower depths. Furthermore, grain size is reduced in and around the shear zone, which agrees with field and laboratory observations where pseudotachylites are embedded in a simultaneously formed mylonite matrix. The decrease in critical stress to initialize localization has important implications for large-scale geodynamics, as this mechanism might induce lithosphere-scale shear zones and subduction initiation. We suggest that the combination of grain size reduction and shear heating explains both the occurrence of intermediate-depth earthquakes and the formation of large-scale shear zones.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 43
Serial Issue: 9
Title: Intermediate-depth earthquake generation and shear zone formation caused by grain size reduction and shear heating
Affiliation: Eidgenoessische Technische Hochschule Zuerich, Institut fuer Geophysik, Zurich, Switzerland
Pages: 791-794
Published: 20150728
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 34
Accession Number: 2015-079080
Categories: Structural geologySeismology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2015270
Illustration Description: illus.
Secondary Affiliation: Johannes Gutenberg University of Mainz, DEU, GermanyUniversite de Lyon-1, FRA, France
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, 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: 201534
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