title: Linking megathrust earthquakes to brittle deformation in a fossil accretionary complex.
abstract: Seismological data from recent subduction earthquakes suggest that megathrust earthquakes induce transient stress changes in the upper plate that shift accretionary wedges into an unstable state. These stress changes have, however, never been linked to geological structures preserved in fossil accretionary complexes. The importance of coseismically induced wedge failure has therefore remained largely elusive. Here we show that brittle faulting and vein formation in the palaeo-accretionary complex of the European Alps record stress changes generated by subduction-related earthquakes. Early veins formed at shallow levels by bedding-parallel shear during coseismic compression of the outer wedge. In contrast, subsequent vein formation occurred by normal faulting and extensional fracturing at deeper levels in response to coseismic extension of the inner wedge. Our study demonstrates how mineral veins can be used to reveal the dynamics of outer and inner wedges, which respond in opposite ways to megathrust earthquakes by compressional and extensional faulting, respectively.
authors.affiliation: Institute of Geological Sciences, University of Bern, Baltzerstrasse 1+3, Bern CH-3012, Switzerland.
authors.forename: Armin
authors.initials: A
authors.lastname: Dielforder
authors.affiliation: 1] Institute of Geological Sciences, University of Bern, Baltzerstrasse 1+3, Bern CH-3012, Switzerland [2] Center for Space and Habitability, University of Bern, Sidlerstrasse 5, Bern CH-3012, Switzerland.
authors.forename: Hauke
authors.initials: H
authors.lastname: Vollstaedt
authors.affiliation: Institute of Earth Surface Dynamics, University of Lausanne, Gêopolis 4634, Lausanne CH-1015, Switzerland.
authors.forename: Torsten
authors.initials: T
authors.lastname: Vennemann
authors.affiliation: Institute of Geological Sciences, University of Bern, Baltzerstrasse 1+3, Bern CH-3012, Switzerland.
authors.forename: Alfons
authors.initials: A
authors.lastname: Berger
authors.affiliation: Institute of Geological Sciences, University of Bern, Baltzerstrasse 1+3, Bern CH-3012, Switzerland.
authors.forename: Marco
authors.initials: M
authors.lastname: Herwegh