Seismic hazard estimates for the area of Pylos and surrounding region (SW Peloponnese) for seismic and tsunami risk assessment

摘要

This paper summarizes the activity developed for the seismic hazard assessment of the Pylos broader area in the framework of the SEAHELLARC project. In addition to the geological, geophysical, and seismological information available in literature, the definition of the seismogenic zones, applied for seismic hazard assessment, was based on the results of the active and passive seismic experiments performed during this project. In particular, a new earthquake catalogue covering the period 550 B.C. to 2009 was compiled. A logic tree with 24 branches has been constructed: it consists of two zonations, two approaches for the seismicity model definition, two methods for maximum magnitude estimate, and four attenuation relations for horizontal peak ground acceleration (PGA). One of the zonations used was specially developed for the Pylos broader area during the SEAHELLARC project: it is notably different from the national model while the national model, with marginal modifications, was accepted for the seismic sources far away from the study area. The results are presented in forms of separate seismic hazard maps of the broader Pylos area, seismic hazard curves and uniform hazard response spectra for Pylos town, for different soil types, suitable for a seismic risk assessment. In addition, a soil seismic hazard map has been elaborated for the Pylos area: it takes into consideration the specific soil types at any sites. Pylos is characterized by a high seismic hazard (PGA around 0.5 g for a 475-year return period on rock), remarkably lower, anyway, than that of the Ionian islands. The widespread presence of rock around the town does not suggest the possibility of unexpected high ground motions. The identification of the possible earthquakes capable of generating tsunamis dangerous for Pylos town has been based on the deaggregation of the hazard results and considerations on the seismic faults identified in the Ionian Sea.