Estimates of fault strength from the Variscan foreland of the northern UK

Copley, Alex and Woodcock, Nigel H. (2016) Estimates of fault strength from the Variscan foreland of the northern UK. Earth and Planetary Science Letters, 451. pp. 108-113. ISSN 0012-821X DOI https://doi.org/10.1016/j.epsl.2016.07.024

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Abstract

We provide new insights into the long-standing debate regarding fault strength, by studying structures active in the late Carboniferous in the foreland of the Variscan Mountain range in the northern UK. We describe a method to estimate the seismogenic thickness for ancient deformation zones, at the time they were active, based upon the geometry of fault-bounded extensional basins. We then perform calculations to estimate the forces exerted between mountain ranges and their adjacent lowlands in the presence of thermal and compositional effects on the density. We combine these methods to calculate an upper bound on the stresses that could be supported by faults in the Variscan foreland before they began to slip. We find the faults had a low effective coefficient of friction (i.e. 0.02–0.24), and that the reactivated pre-existing faults were at least 30% weaker than unfaulted rock. These results show structural inheritance to be important, and suggest that the faults had a low intrinsic coefficient of friction, high pore-fluid pressures, or both.

Item Type:	Article
Uncontrolled Keywords:	2016AREP; IA71
Subjects:	02 - Geodynamics, Geophysics and Tectonics
Divisions:	02 - Geodynamics, Geophysics and Tectonics 08 - Green Open Access
Journal or Publication Title:	Earth and Planetary Science Letters
Volume:	451
Page Range:	pp. 108-113
Identification Number:	https://doi.org/10.1016/j.epsl.2016.07.024
Depositing User:	Sarah Humbert
Date Deposited:	24 Feb 2017 18:18
Last Modified:	24 Feb 2017 18:18
URI:	http://eprints.esc.cam.ac.uk/id/eprint/3833

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