Review of methods that implement active faults characterization for PSHA in Southern Spain. Preliminary results of the application of the FAMS method.

Incorporating faults as independent seismic sources in Probabilistic Seismic Hazard Assessment (PSHA) significantly influences the ground motion values when compared to classical zoning methods (CZM). This practice holds particular relevance for populations situated top or near active faults. Some hybrid methods (HM) and fault-based methods, implemented in Spain, show that Peak Ground Acceleration (PGA) values increase in the vicinity of the fault traces. In some cases the hazard levels may double, consistent with the PGA observed in recent earthquakes (Rivas-Medina, A., 2018; Gómez-Novell O., 2020). Despite the existence of methods that combine zones and faults in seismic sources characterization, there is a lack of allocation of seismic potential between these two types of sources. Additionally, there is an increasing use of geological data since seismic catalogs alone are insufficient to fully characterize the seismic potential of faults. This limitation becomes particularly evident in slow deformation zones, such as southeastern Spain, where the recurrence period of faults exceeds the temporal coverage of the seismic catalog.

The present investigation addresses two key aspects: how to quantify the geological information of the faults and transfer it to recurrence models, and how to distribute the seismic potential of the region between faults and zone. This research contemplates two steps. In the first step, four methods were applied: 1) Moment rate-based method, 2) Slip rate-based method, both proposed by Bungum (2007); 3) the hybrid method developed by Rivas-Medina et al. (2018), which considers both zone-type and fault-type sources; and 4) SHERIFS, a fault system-based assessment proposed by Cartier et al. (2019). In the second step, Faults and Area Moment Sharing (FAMS) (Ornelas-Agrela et al., 2022*) is applied. This new method enables characterizing the faults based on their associated seismicity, improving the distribution of seismic potential between faults and zones. The five methods were applied to multiple seismogenic zones within southeastern Spain, recognized as one of the most seismically active areas in the country. An analysis was conducted, highlighting the sensitivity of the results of PSHA implementation. The preliminary results of the FAMS method application are presented.

_{* first presented by Ornelas-Agrela, A. et al. at the Iberfault2022 congress in Teruel, Spain.}