The active Nea Anchialos Fault System (Central Greece): comparison of geological, morphotectonic, archaeological and seismological data

The Nea Anchialos Fault System has been studied integrating geological, morphological, structural, archaeological and seismic data. This fault system forms the northern boundary of the Almyros Basin which is one of the Neogene-Quaternary tectonic basins of Thessaly. Specific structural and geomorphological mapping were carried out and fault-slip data analysis allowed the Late Quaternary palaeo-stress field to be estimated. The resulting N-S trending purely extensional regime is consistent with the direction of the T-axes computed from the focal mechanisms of the summer 1980, Volos seismic sequence and the April 30, 1985 Almyros earthquake. A minor set of structural data indicates a WNW-ESE extension which has been interpreted as due to a local and second order stress field occurring during the N-S regional extension. Furthermore, new archaeological data, discovered by the author, have improved morphology and tectonics of the area also allowing a tentative estimate of the historic (III-IV century AD. to Present) fault slip rate. Several topographic profiles across the major E- W topographic escarpment as well as along the streams, have emphasised scarps and knick-points, further supporting the occurrence of very recent morphogenic activity. In the last section, the structural, morphological and archaeological data are compared with the already existing seismological data and their integrated analysis indicates that the Nea Anchialos Fault System has been active since Lower(?)-Middle Pleistocene