The 20th International Geophysical Congress and Exhibition of Turkeyi, 25-27 November 2013, Antalya Tectonic regime of the southern, central part of the Mygdonia basin by applying 3D TEM modeling Pantelis Soupios 1 , Pavel Barsukov 2 , Marcus Gurk 3 and Alexandros Savvaidis 4 1 Laboratory of Geophysics and Seismology Technological Educational Institute of Crete Chania Greece, (soupios@chania.teicrete.gr) 2 Russian Academy of Sciences Geoelectromagnetic Research Centre IPE RAS Russia 3 Institute of Geophysics and Meteorology University of Cologne Germany 4 Institute of Earthquake Seismology and Earthquake Engineering Ag.Georgiou 5 Pylaia P.O. Box 53, 55102 FinikasThessaloniki Greece Abstract: The transient electromagnetic method (TEM) has gained increasing popularity over the last years especially in hydrogeophysical and geotectonic applications. Many portable systems for TEM measurements are commercially available. The TEM-Fast 48HPC was used for collecting the soundings. The main purpose of this work was the definition of the geotectonic characteristics of the study area. Detailed geological survey was applied prior the geophysical measurements and all the available borehole logs were collected. All the data integrated to produce a secure and reliable geotectonic model of the area under investigation. Joint systems of faults was detected which are in aggreement with the recent geophysical and tectonic studies in the area. This work shows clearly the applicability and efficiency of the TEM in studying complex geotectonic environment. Keywords: Volvi Lake, TEM, Tectonic, 3D TEM modeling INTRODUCTION The geophysical techniques offer a suitable method for depicting the tectonic and other subsurface characteristics of an area under investigation. Among all geophysical techniques (Gravity, GPR, Magnetics, Resistivity, Seismic refraction, etc.) electromagnetic methods are undoubtedly one of the leading ones in the exploration and management of sedimentary environment (Barsukov et al. 2007). TEM method has been used worldwide for many environmental surveys (including geotectonic studies) since several theoretical studies on the applicability of the method for environmental investigation was undertaken. The transient electromagnetic (TEM) method is a fast and cost-effective method for exploring the subsurface and is of interest in this work. This paper describes a recent evaluation study of the applicability of a simple-fast-robust-portable TEM system, the TEM-Fast 48HPC developed by AEMR Ltd, using single loop 50x50m (coincident loop) for shallow-depth geological mapping for depicting the tectonic regime of the southern part of the central part of the Mygdonia basin in northern Greece, close to Thessaloniki city. GEOLOGICAL and TECTONIC SETTINGS of THE STUDY AREA The Mygdonian basin, situated between the two lakes Volvi and Lagada ca. 45 km northeast of Thessaloniki, is a Neogene graben structure with significant seismic activity along distinct normal fault patterns (Karagianni et al. 1999). Fluvioterrestrial and lacustrin sediments (approximately 200- 500 m thick) overlie the basement composed of gneiss schist. The faults in the broader area have E-W, NW-SE, and NE-SW directions. The fault of Gerakarou-Nikomidino-Stivos-Peristerona is at the area of study and in particular we are interested on revealing any of the shallow normal faults close to the surface using geophysical data. Those faults are supposed to follow the general strike direction of the fault that is almost E-W, however strike directions of WNW-ESE to ENE-WSW are also found in the area. -365-