Frictional characteristics of oceanic transform faults: progressive deformation and alteration controls seismic style

Cox, Sophie, Ikari, Matt J., MacLeod, Christopher J. ORCID: https://orcid.org/0000-0002-0460-1626 and Fagereng, Åke ORCID: https://orcid.org/0000-0001-6335-8534 2021. Frictional characteristics of oceanic transform faults: progressive deformation and alteration controls seismic style. Geophysical Research Letters 48 (24) , e2021GL096292. 10.1029/2021GL096292

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Abstract

Oceanic transform faults are inferred to be weak relative to surrounding oceanic crust and primarily slip aseismically. Neither their weakness nor tendency to creep are well-explained. We test the effects of fault-rock evolution on oceanic transform fault frictional strength and stability using direct-shear experiments (at room temperature, 10 MPa normal stress, and fluid-saturated conditions) on dolerite from the East Pacific Rise and natural fault rocks from the exhumed Southern Troodos Transform, Cyprus. Dolerites and cemented breccias are frictionally strong (μ = 0.52–0.85) and velocity-weakening (strength decreases with increasing slip velocity, characteristic of earthquakes). In contrast, matrix-rich chlorite-bearing fault breccias and gouges are frictionally weak (μ = 0.25–0.48) and velocity-strengthening (characteristic of stable creep). This transition implies that seismic behavior is controlled by degree of damage and alteration, such that earthquakes can nucleate within relatively intact oceanic crust, whereas fault segments of increased damage and chlorite content tend to slip aseismically.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Environmental Sciences
Additional Information:	This is an open access article under the terms of the Creative Commons Attribution License
Publisher:	Wiley
ISSN:	0094-8276
Funders:	NERC
Date of First Compliant Deposit:	11 January 2022
Date of Acceptance:	7 December 2021
Last Modified:	17 May 2023 00:16
URI:	https://orca.cardiff.ac.uk/id/eprint/146531

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