The seismically active Atalanti fault in Central Greece: A steeply dipping fault zone imaged from magnetotelluric data

The WNW-ESE striking Atalanti fault is one of the large fault segments of the ca. 110-km-long WNW-ESE trending Sperchios-Chalkis Fault System that subsided along the NE slopes of the Kalidromon and Chlomo Mts. in Central Greece forming an extensive graben similar to the Corinthiakos Gulf. Although, the fault is characterized by recent seismic activity, it has up to now not been investigated by means of geophysical methods that could define the geometrical features of the structure in depth.Magnetotelluric measurements performed along three 14-km-long profiles A, B, and C and across the fault with a total of 28 stations indicate that its geoelectric strike is WNW-ESE. Two-dimensional bimodal and the determinant of the impedance tensor inversions were applied to the data. The best data fit was achieved using the determinant data. The resulting 2D models were further interpreted both separately and all together in order to define the geometry of the structure down to a depth of several kilometers.The derived resistivity model defines that the Atalanti fault strikes WNW-ESE and forms a damage zone that contains two high-angle fault branches that dip at angles of 60° and 80° respectively. Thus, the interpreted geometry of the Atalanti fault and consequently the Sperchios-Chalkis Fault System differs from previous interpretation of a low-angle extensional crustal structure. In addition, the electrical resistivity model indicates the subsidence of the overthrust of the Internal Hellenides over the Parnassos zone toward the NNE from a depth of 2 km to deeper crustal levels due to the Atalanti fault.

► We model the crustal structure of the Atalanti Fault Zone. ► We acquired magnetotelluric data and propose resistivity models along three profiles. ► The Atalanti fault strikes WNW-ESE forming a damage zone of two high angle faults. ► The faults dip NNE at angles 60° and 80°, precluding a low angle extensional system.