Campbell, LR, Phillips, RJ, Walcott, RC et al. (1 more author) (2019) Rupture geometries in anisotropic amphibolite recorded by pseudotachylytes in the Gairloch Shear Zone, NW Scotland. Scottish Journal of Geology, 55 (2). pp. 75-92. ISSN 0036-9276
Abstract
Recent earthquakes involving complex multi-fault rupture have increased our appreciation of the variety of rupture geometries and fault interactions that occur within the short duration of coseismic slip. Geometrical complexities are intrinsically linked with spatially heterogeneous slip and stress drop distributions, and hence need incorporating into seismic hazard analysis. Studies of exhumed ancient fault zones facilitate investigation of rupture processes in the context of lithology and structure at seismogenic depths. In the Gairloch Shear Zone, NW Scotland, foliated amphibolites host pseudotachylytes that record rupture geometries of ancient low-magnitude (≤ MW 3) seismicity. Pseudotachylyte faults are commonly foliation parallel, indicating exploitation of foliation planes as weak interfaces for seismic rupture. Discordance and complexity are introduced by fault segmentation, stepovers, branching and brecciated dilational volumes. Pseudotachylyte geometries indicate that slip nucleation initiated simultaneously across several parallel foliation planes with millimetre and centimetre separations, leading to progressive interaction and ultimately linkage of adjacent segments and branches within a single earthquake. Interacting with this structural control, a lithological influence of abundant low disequilibrium melting-point amphibole facilitated coseismic melting, with relatively high coseismic melt pressure encouraging transient dilational sites. These faults elucidate controls and processes that may upscale to large active fault zones hosting major earthquake activity.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2019 The Author(s). Published by The Geological Society of London for EGS and GSG. All rights reserved. This is an author produced version of a paper accepted for publication in the Scottish Journal of Geology. Uploaded in accordance with the publisher's self-archiving policy. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst of Geophysics and Tectonics (IGT) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 23 Jul 2019 10:46 |
Last Modified: | 19 Jul 2020 00:38 |
Status: | Published |
Publisher: | Geological Society |
Identification Number: | 10.1144/sjg2019-003 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:148822 |