Towards a new seismic hazard assessment in Spain

Abstract

Seismic hazard is an evolving science that is fed by geological and seismological studies. As new data and models arise, the revision of hazard maps is compelling. Additionally, understanding the nature and the sources of the uncertainties involved in seismic hazard analyses is essential in order to reduce them. In this context, Spain is not an exception and a move towards a reassessment of the national hazard maps is pertinent. Several hazard-controlling factors needing to be updated and eventually revaluated are identified in this work in progress. The first one concerns the seismic catalogue. It must be homogenised, incorporating data from neighbouring countries and correlating magnitude scales for different regions and recording periods. A second factor refers to seismicity characterization by zoning and zoneless models: Neotectonic, seismological and other geological data that justify the development of a new zoning model for Spain and adjacent areas are disclosed. Revaluation of seismic areas that are traditionally considered as stable but show evidence of seismic activity at present and during Quaternary times needs to be considered. The interest of developing a neotectonic characterization of active faults is advanced. For zoneless models, the different elements that define the continuous spatial variation of the activity rate density have to be examined. For a zoneless model based on kernel functions, these elements would be the specific type of kernel function, the bandwidth and the reference years. A third factor requiring a modern analysis refers to the implementation of different strong motion prediction models. These include models based on local data and developed with data from other regions. Special attention is paid to the application of the next generation attenuation models originally developed for western North America to Spain. Criteria for selecting different models must be clearly and thoughtfully enumerated. The final goal of this work is to assess the variability of seismic hazard results to the new data and models that are becoming available. Such information will be of indubitable interest for forthcoming versions of the seismic code, national annexes of Eurocode 8 and research projects fomented by the Spanish Nuclear Security Council