Splay fault permeability governs fluid–structure interaction in accretionary wedges

Julve Lillo, Joaquin ORCID: https://orcid.org/0000-0002-9430-6814, Fagereng, Ake ORCID: https://orcid.org/0000-0001-6335-8534, Toffol, Giovanni ORCID: https://orcid.org/0000-0001-7776-3602 and Ujiie, Kohtaro 2026. Splay fault permeability governs fluid–structure interaction in accretionary wedges. Geophysical Research Letters 53 (5) , e2025GL120143. 10.1029/2025gl120143

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Abstract

Plain Language Summary: Subduction zones are areas where one tectonic plate slides beneath another, and they produce the world's largest earthquakes. In these settings, faults called splay faults cut through the upper plate and connect to the deeper plate boundary fault. Fluids circulating in these zones—like water trapped in the rocks—can influence whether faults slowly slip or break suddenly in earthquakes. But how these fluids move, and what controls their pathways, is still not fully understood. This study combines geological observations of ancient, exposed splay faults in Japan with computer simulations that track how fluids and rock deformation interact over thousands of years. The results show that the permeability of splay faults—that is, how easily fluids can move along or through them—is a key factor that shapes where fluids go, how rocks break, and where earthquake‐related features like veins can form. These findings help connect short‐term geophysical observations with long‐term geological processes. Understanding the role of fault permeability may improve how we assess earthquake hazards in areas where fluids and complex fault systems interact.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Earth and Environmental Sciences
Additional Information:	License information from Publisher: LICENSE 1: URL: http://creativecommons.org/licenses/by/4.0/
Publisher:	Wiley
ISSN:	0094-8276
Date of First Compliant Deposit:	6 March 2026
Date of Acceptance:	18 February 2026
Last Modified:	10 Mar 2026 10:16
URI:	https://orca.cardiff.ac.uk/id/eprint/185561

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