The study of active faults and deformation of the Earth's surface has made, and continues to make, significant contributions to our understanding of earthquakes and the assessment of seismic related hazard. Active faulting may form and deform the Earth's surface so that records are documented in young sediments and in the landscape. Field studies of recent earthquake ruptures help to constrain earthquake source parameters and to identify previously unknown active structures. The insights gleaned from recent earthquakes can be applied to study past earthquakes. Paleoseismology and related disciplines such as paleogeodesy and paleotsunami investigations still are the primary tools to establish earthquake records that are long enough to determine recurrence intervals and long-term deformation rates for active faults. Multidisciplinary data sets accumulated over the years have brought unprecedented constraints on the size and timing of past earthquakes and allow deciphering shorter-term variations in fault slip rates or seismic activity rates, as well as the interaction of single faults within fault systems. This wide range of methods leads to a wide range of uncertainties in the definition of what is an active fault, which parameters are entered in fault databases, which consequently conditions the strategy used to transfer earthquake-fault data into fault models suitable for probabilistic SHA. Which uncertainty can be quantified by geologists and how can it be made easily accessible for proper usage in hazard computation is a fundamental question that the FAULT2SHA ESC working group (www.fault2sha.net) is attempting to tackle.
This FAULT2SHA session aims to spark a discussion between field earthquake geologists, crustal deformation modellers and fault modellers/seismic hazard practitioners around fault-related uncertainty issues and their inclusion in fault-based PSHA. We welcome contributions describing and critically discussing approaches used to study active faults as well as presentations discussing existing efforts on how fault-related information is translated into dedicated databases of primary surface information and then into 3D fault models. We particularly encourage contributions related to local studies of fault systems where specific issues could be debated on either fault data collection aspects, databases questions and/or fault hazard modelling