Strain localization is a fundamental process controlling deformation at plate boundaries and the strength evolution of the lithosphere. The development of localized high-strain zones requires some form of strain weakening. Such weakening can be caused by a number of processes and may originate at pre-existing heterogeneities. The strength profile of the lithosphere is thought to accommodate deformation at two main regions: 1) the brittle-ductile transitional zone, considered the zone of maximum strength of the continental crust, where (seismic) brittle faulting and combined crystal-plasticity mechanisms are active, and ii) the lithospheric mantle, mainly dominated by viscous flow mechanisms, in which a major strength contrast exists at the interface crust/mantle. Such regions are the locus of the nucleation of major zones of weakening, i.e. shear zones, which are thought to exert a strong control on the way strain is distributed/localized and subsequently partitioned along the lithosphere. These characteristics have marked implications for faulting processes, earthquake dynamics and the overall motion of tectonic plates.

We invite contributions that address strain localization at depths ranging from the brittle-ductile transition to the upper mantle. We welcome experimental, microstructural and field studies, as well as numerical modelling of relevant deformation mechanisms and macroscopic strain localization. We aim to advance in the understanding of the role and dynamic interplay of fracturing, viscous flow, fluid-rock interaction and thermo-mechanical properties in strain localization and their potential implications for the strength distribution throughout mid-lower crust and upper mantle.