Lithospheric rheology and earthquake processes in strike-slip plate boundaries

Abstract

Understanding the rheology of the lithosphere along tectonic plate boundaries has important implications for understanding earthquake processes and assessing seismic risk.  However, there is considerable uncertainty regarding the strength of the deeper parts of the lithosphere in plate-bounding strike-slip faults.  This talk will present geological data from major strike-slip plate boundaries, such as the San Andreas fault system, USA, the Baja California shear zone, Mexico, and the Bogota Peninsula shear zone, New Caledonia.  Analysis of upper mantle and lower crust xenoliths from the San Andreas fault and the Baja California shear zone, indicates that differential stress remains constant, and low, with depth.  This result is not consistent with the typical lithospheric strength profiles constructed from deformation experiments and used for modelling lithospheric processes.  Peridotites from the Bogota Peninsula shear zone, which comprises the exhumed mantle section of an oceanic transform zone, record the mechanical interaction between the upper, “brittle” part of the oceanic lithosphere, and the underlying viscously deforming upper mantle, during earthquake rupture.  The results from the three study areas indicate that crust and lithospheric mantle act together as an integrated system, and allow us to build a picture of earthquake-related deformation in the upper mantle during the seismic cycle.

Biography

Vasileios Chatzaras is a Lecturer in the School of Geosciences at the University of Sydney. 

He received a PhD in Geology from the University of Patras, Greece in 2010, and held a postdoctoral research position at Boston College, and a Marie Curie postdoctoral research fellowship at the University of Wisconsin-Madison and Utrecht University.  His research focuses on understanding lithospheric deformation, and how deformation processes in the lower crust and upper mantle may affect seismicity.