Probabilistic Seismic Hazard Assessment for the Broader Messinia (SW Greece) Region

Messinia is located in SW Peloponnese (Greece), in the vicinity of the Hellenic Arc which is one of the most seismically active areas of Europe. The arc is dominated by reverse faulting, whereas normal faults are mapped onshore, mainly striking N-S. Large earthquakes have occurred in the study area, both in the historical and instrumental periods. In the present study, a Probabilistic Seismic Hazard Assessment (PSHA) is applied to estimate the Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV), Peak Ground Rotational Acceleration (PGRA) and Peak Ground Rotational Velocity (PGRV) for the broader Messinia region. PGRA and PGRV are not often examined in detail in the literature, even though they are useful for the evaluation of the possible damages in structures. The widely used approach proposed by Cornell and McGuire is implemented taking into account: (a) the seismotectonic model proposed by Seismic Hazard Harmonization in Europe (SHARE), (b) an earthquake catalogue for the instrumental period and (c) Ground Motion Prediction Equations (GMPEs) proposed for the Greek territory. The computational grid spacing for Messinia was set to 1 km, in order to accurately calculate the hazard parameters and to reduce the bias of the results through interpolation processes. For PGA and PGV, a logic tree approach is considered, where every branch is a hybrid version of each GMPE considering the percentage of the type (normal or non-normal) of focal mechanisms for all zones of the seismotectonic model. The results show an increase of the hazard values in the NW part of the study area, where the Greek Building Code provides lower PGA values. In addition, hazard curves in terms of PGA for multiple probabilities of exceedance in 50 years are determined for five major towns of Messinia, i.e. Kalamata, Messini, Filiatra, Kyparissia and Pylos. Kyparissia has the higher hazard in all probabilities of exceedance, which is in full agreement with the PGA and PGV results. Pylos and Filiatra have intermediate to high hazard, whereas Kalamata and Messini show intermediate hazard values. Furthermore, the Uniform Hazard Spectrum (UHS) in terms of Spectral Acceleration for the same towns is computed. The latter provides essential information about the design parameters. Lastly, the results are compared to the seismic histories of the five major towns in terms of European Macroseismic Scale (EMS98) intensity, plotted for the last 200 years.