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Probabilistic Seismic Hazard Assessment of the Eastern Betics Shear Zone (SE Spain) Using a Geological Fault-Based Source Modelling Approach

Session: Probabilistic Seismic Hazard Assessment: Where Do We Go from Here? I

Type: Oral

Date: 4/20/2021

Presentation Time: 09:45 AM Pacific

Description: 

In this study we present a probabilistic seismic hazard assessment (PSHA) for SE Spain including the Eastern Betics Shear Zone (EBSZ) faults as the main seismogenic sources. Contrasting with previous studies in Spain, here the earthquake occurrence is modelled considering different hypotheses of fault and multi-fault ruptures at the whole fault system scale and weighted in a logic tree. The modelling of the magnitude frequency distributions (MFDs) of each hypothesis is achieved by using the novel SHERIFS methodology with mainly geological fault data as inputs. The logic tree weighting is based on the MFD agreement with the rates of the regional seismic catalogue and the available paleoseismic data. The resulting hazard analysis shows a clear control of the EBSZ fault sources in the seismic hazard even for short return periods (e.g., 475-year), increasing drastically the hazard levels in the regions close to the fault traces (~ 20 km) with respect to area source-based PSHAs. These hazard values however, strongly depend on the fault slip rates, as both higher acceleration values and territorial extension of the fault influence appear around the highest slip rate faults of the system (Alhama de Murcia and Carboneras faults). Conversely, lower slip rate faults have a much more limited impact in the seismic hazard and in some cases even negligible (Palomares fault). For the 475-year return period and at near-fault sites, the models are more consistent with the ground motion recorded in the 2011 Mw 5.2 Lorca earthquake rather than the national hazard maps, suggesting a better performance of our approach. Among the limitations, slip rates related to the lack of paleoseismic studies in selected faults, have important repercussions on the seismic hazard that can bias the results and, therefore, compromise the reliability of the hazard estimations. These are key problematics to discuss that have an impact on the present study and set insights for further research in the study area or even in other similar regions worldwide.

Presenting Author: Octavi Gómez-Novell

Student Presenter: Yes

Authors