Hora: 12:00
Lloc: Sala d'actes de l'Institut de Ciències de la Terra Jaume Almera

Stéphane Baize (Institut de Radioprotection et Sûreté Nucléaire, França)

Seismic hazard assessment (SHA)
implicitly covers 2 issues related to geology, which require distinct engineering strategies of mitigation: seismic ground shaking and surface faulting. Geological data are used in SHA to define and describe the earthquake sources, both zones of diffuse seismicity and active faults. In nuclear industry, the required level of safety is very high and entails to explore low probabilities of exceedance of hazard level, thus exploring the earthquake history several tens of thousands years backwards in time. This can only be performed through on-fault and off-fault paleoseismology, especially in intraplate regions where recorded and historical seismicity
are far from representing the earthquake cycle.

Damaging earthquakes of the past decade could have been foreseen with available geological data (e.g. Sumatra 2004, Sichuan 2008, L'Aquila 2009); others not (e.g. Chuetsu-Oki 2007, Haiti 2010; Canterbury 2010-11). Tohoku, 2011 drastically showed that unexpected -although physically possible seismic scenarios could occur and induce dramatic effects. Following this accident, a continental-scale effort was asked by the European Council to the national agencies and operators in order "to assess how nuclear installations can withstand the consequences of various extreme external events". The reassessment of Japanese NFs was fed by new and in-depth geological studies, including paleoseismological investigations. With respect to the "surface faulting issue", 4 NFs are currently under inspection, and 2 others are discarded because of the presence of a capable fault beneath the site. Recent developments in earthquake geology and new data acquisition also led in some cases (e.g. in USA and Eu Increasing the
geological databases is a must in nuclear safety because it improves the SHA. Future nuclear sites should be investigated in detail before building because finding out an active fault at a short distance (less than 25 km) after licensing can lead to expensive investigations, analyses, discussions and delays of operation. In nuclearized countries, many NFs were licensed early in the "earthquake geology" history and a serious updating can be expected in a close future, including Spain and France.