Clustering of earthquakes along the Pidima-Anthia normal fault: New data from palaeoseismology and tectonic geomorphology and their significance on the earthquake's regularity and recurrence across southern Greece

Abstract

The Pidima-Anthia Fault provides an opportunity to unravel the long palaeoseismic records of the Eastern Messinia Fault Zone (EMFZ) that defines the western border of the Taygetos Mtn range in Peloponnese (southern Greece). This fault zone is segmented and includes a complex system of primarily normal fault segments dipping westwards with a strike of NNW-SSE to N–S, with a traceable length from 6 to 10 km. We applied geomorphological and palaeoseismological analysis across the Pidima-Anthia Fault. The palaeoseismological trench performed across the Pidima-Anthia Fault provide evidence for five M > 6.4 earthquakes hosted on this fault and indicate an apparent slip rate of 0.23 mm/a. Geomorphologically, based on modelling the triangular facets, we estimated the slip rate as 0.28–0.44 mm/a. These data highlight that the slip rate of the fault is remarkably stable for the approximately 17 ka period, and that this duration is enough for a morphogenic active fault to create seismic landscapes. The earthquake history of the Pidima-Anthia Fault allows its comparison with six other known faults that dominate the earthquake history of southern Greece. The pattern of earthquake history in southern Greece shows clustering features (“Wallace-type” behaviour) during Late Quaternary. In particular, the Pidima-Anthia Fault's seismic history resembles with time predictable earthquakes and clustering during the Holocene. Overall, clustering appears prevalent in earthquake behaviour in southern Greece. However, the Pidima-Anthia Fault during the current period (i.e., post 1 ka A.D.)does not display cluster time-predictable behaviour and a strong earthquake can happen at any time.