The Contribution of Palaeoseismology to Seismic Hazard Assessment in Site Evaluation for Nuclear Installations

In the framework of site evaluation/re-evaluation procedures for nuclear power plants and other nuclear installations, this publication aims at encouraging and supporting Member States, especially from newcomer countries, to include paleoseismic investigations into the geologic database. In fact, paleoseismology is not just a crucial discipline for Fault Displacement Hazard Assessment (FDHA) but also an indispensable tool for Seismic Hazard Assessment (SHA), as recommended in the reference IAEA Safety Guide (IAEA SSG-9 [1]). Within this scope, this document provides an updated review of the state of the art of paleoseismology, integrated with practical recommendations addressed to Member States, aiming to emphasize the value of earthquake geology studies for nuclear safety. Paleoseismic investigations in the context of site evaluation of nuclear installations, as described in the IAEA SSG-9 [1], have the following main objectives: •Identification of seismogenic structures based on the recognition of effects of past earthquakes in the region; •Improvement of the completeness of earthquake catalogs, through the identification and dating of ancient moderate to large earthquakes, whose trace has been preserved in the geologic record; •Estimation of the maximum seismic potential associated with an identified seismogenic structure/source, typically on the basis of the amount of displacement per event (evaluable in paleoseismic trenches), as well as of the geomorphic and stratigraphic features interpretable as the cumulative effect of repeated large seismic events (concept of ‘seismic landscape’); •Rough calibration of probabilistic seismic hazard assessment (PSHA), by using the recurrence interval of large earthquakes detectable by paleoseismic investigations, and providing a ‘reality check’ based on direct observations of earthquake environmental effects.