The central and eastern parts of the basin belong to the Serbomacedonian massif, which is the most seismotectonically active zone in northern Greece, while its western part belongs to the Circum Rhodope zone. The basement of the area consists mainly of gneiss, amphibolites, two-mica schist and marble intrusions. The sediments that fill the basin can be classified into two main units: the lower unit, namely the Pro-Mygdonian system (mainly conglomerates, sandstones, silt-sand sediments and red-beds), which was deposited during the Neogene in the Pro-Mygdonian basin and the upper unit, namely the Mygdonian system (mainly fluviolacustrine, deltaic, lacustrine, lagoonal and estuarine deposits), which was deposited during the Quaternary within the younger grabens of the basin (Psilovikos, 1997; Sotiriadis et al., 1983). The Pro-Mygdonian and Mygdonian systems form a sedimentary "package", with a thickness which varies along the central axis of the basin from 140m close to Lake Volvi (Raptakis et al., 2005) to 400m at the western edge of Lake Langada (BRGM, 1971).

At present, the Mygdonia basin is subjected to the N-S extension of the Aegean Sea and the westward movement of the North Anatolia Fault. The main active faults in the area strike in NW-SW, E-W or ENE-WSW direction. The E-W trending faults are mainly dip-slip, while the NW-SW and ENE-WSW occasionally show strike-slip components of movement.

Figure 1: Neotectonic faults (after Tranos et al., 2003) and extensional velocities (arrows; Papazachos et al., 2001) for the broader EUROSEISTEST area. Figure is from Paradisopoulou et al. (2006) and more information on individual seismotectonic features can be found therein.

The fault zone forming the southern boundaries of the Mygdonia graben, was in fact related to 1978, M6.5 earthquake which affected the epicentral area, as well as the city of Thessaloniki. The locations of the largest events of the 1978 earthquake sequence are shown in Figure 2.

Figure 2: Map showing the broader region of occurence of the 20 June 1978 (M6.5) earthquake sequence. Epicenter and focal mechanism (Liotier, 1989) of the mainshock (red) and epicenters of the largest events of the sequence (green, yellow) (Carver and Bollinger, 1981) are also depicted. Dotted lines mark the Mygdonia graben and surface ruptures after the 1978 earthquake (Mountrakis et al., 1983) are shown as red lines.

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  • Papazachos C. B., D. A. Vamvakaris, G. N. Vargemezis and E. V. Aidona (2001). A study of the active tectonics and deformation in the Mygdonia basin (N. Greece) using seismological and neotectonic data, Bull. Geol. Soc. Greece XXXIV, 303 - 309.
  • Psilovikos A. (1977). Paleogeographic development of the basin and lake of Mygdonian (Lagada - Volvi area, Greece), PhD Thesis, Department of Geology, Aristotle University of Thessaloniki (in Greek).
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  • Tranos M. D., E. E. Papadimitriou and A. A. Kilias (2003). Thessaloniki-Gerakarou Fault Zone (TGFZ): the western extension of the 1978 Thessaloniki earthquake fault (Northern Greece) and seismic hazard assessment, J. Struct. Geol. 25, 2109 - 2123.