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A geological explanation for intraplate earthquake clustering complexity : the zeolite-bearing fault/fracture networks in the Adamello Massif (Southern Italian Alps).

Dempsey, E.D. and Holdsworth, R.E. and Imber, J. and Bistacchi, A. and Di Toro, G. (2014) 'A geological explanation for intraplate earthquake clustering complexity : the zeolite-bearing fault/fracture networks in the Adamello Massif (Southern Italian Alps).', Journal of structural geology., 66 . pp. 58-74.

Abstract

Interconnected networks of faults and veins filled with hydrothermal minerals such as zeolite are widespread in many orogenic terrains. These fractures commonly form at relatively low temperatures (e.g. < 200°C) late in the tectonic history and represent significant phases of fluid flow and mineralisation during exhumation. Zeolite-bearing fractures spatially associated with the Gole Larghe Fault Zone in the Southern Italian Alps are preserved along an interconnected network of variably orientated pre-existing structures. They show evidence of repeated episodes of hydraulic tensile fracturing and small magnitude (total offsets <5m) shear displacements. We use geological observations and Coulomb stress modelling to propose that repeated seismogenic rupturing of larger offset faults led to local stress transfer and reactivation of widely distributed smaller pre-existing structures in the wall rocks. The differing orientations of the pre-existing features within what is assumed to have been a single regional stress field led to the simultaneous development of reverse, strike-slip and extensional faults. The kinematic diversity and cyclic nature of the hydraulically-assisted deformation suggest that the mineralised fracture systems represent a geological manifestation of intraplate micro-earthquake clusters associated with fluid migration episodes in the upper crust. Our observations highlight the role of crustal fluids and structural reactivation during earthquakes.

Item Type:Article
Keywords:Faulting, Earthquake Clusters, Hydraulic fracturing, Stress Inversions, Stress transfer, Zeolites.
Full text:(AM) Accepted Manuscript
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Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1016/j.jsg.2014.04.009
Publisher statement:NOTICE: this is the author’s version of a work that was accepted for publication in Journal of structural geology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of structural geology, 66, 2014, 10.1016/j.jsg.2014.04.009
Date accepted:28 April 2014
Date deposited:22 May 2014
Date of first online publication:22 May 2014
Date first made open access:No date available

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