Tectonic stress in the Earth’s crust can never be observed directly but it’s in depth understanding is of fundamental importance as it determines how rocks deform, fracture and fold patterns develop and faults nucleate and behave. A refined understanding of tectonic stresses also plays an important role toward seismic hazard assessment as it governs the seismotectonic triggering of active faults. Stress can be studied using brittle deformation structures as natural gauges as those are the direct result of the stress field(s) that the rock experienced and accommodated. A good mechanical understanding of fault and fracture formation is a pre-requisite for fault-kinematic analysis of fault-slip data. Different methods allow to reconstruct the paleostress field from geological data of the present-day stress field from earthquake focal mechanisms. They constrain mainly reduced stress tensors, although a few provide differential stresses, and even fewer both quantities.

The session aims at making the point on the advances in the methods of paleo-stress/strain analysis and evaluate how paleo-stress/strain reconstructions contribute to tectonic studies, both in terms of orientations and magnitudes. We would like to discuss keys and pitfalls in paleostress reconstructions, to move forward the long-lived debate on stress vs. strain vs. kinematic interpretation of fault-slip data and other geological indicators, and estimate to what extent paleostresses can be compared to modern stresses in terms of distribution in time and space and of geological and physical meanings. We emphasize also the need for new improved techniques and for discussing how existing methods can be more thoughtfully combined and applied. Our ultimate wish is to bring together researchers who work on these topics.

We welcome a wide range of contributions focusing on both methodological aspects and regional applications. Special attention shall be paid to the use of hybrid fractures and negative information in paleostress reconstructions, separation of heterogeneous data sets in regional polyphase brittle analysis, reactivation mechanisms and strain partitioning in the brittle regime, as well as modeling studies of stress states at the local or regional scale.