The Carpathian foredeep is a molasse-bearing depression that formed in front of the folded eastern and southern Carpathians in the Late Miocene. Deep seismic reflection/ refraction profiles as well as gravity and thermal studies carried out in the foredeep area of the southern and eastern Carpathians provide information on the crustal structure of the study region. The variability in the reflectivity pattern and crustal thickness shown by the different sectors of the Carpathian foredeep are due to differences in the structure and lithology as well differences in crustal age (Klemperer, 1987; Wever et al., 1987).

The Moesian Platform becomes a very important area concerning gas and oil accumulation after the discovery (1951) of the Tiulenovo (Bulgaria) oil deposit. This fact marked a consider- able development of seismic prospection and exploration drillings. In the next period many deposits were discovered which relieved the structure and tectonics of this platform which is situated between the Carpathians and Balkan Mts. The drilling works intercepted the crystalline basement and evidenced their complex lithology. The basement of the Moesian platform is subdivided into a western, Wallachian, and an east- ern Dobrodjean block, separated by the Intramoesian fault. Whereas the western part is made up of epi and mesometamorphic Precambrian rocks, the eastern sector is characterized by weakly metamorphosed, Upper Vendian-Early Cambrian flyschoid sediments (greenschists). All these crystalline schists were re-worked by Cadomian orogeny (Early Paleozoic) when the Moesian platform has been consolidated (Sandulescu, 1984). The whole Moesian basement is pierced by magmatic rocks of Paleozoic age. The sedimentary cover started with the Cambrian and Ordovician and continued with some stratigraphic hiatuses up to the Neogene and Quaternary. The Alpine orogeny movements have induced a strong and active subsidence of the platform area where a thick sedimentary cover accumulated (of 10 km maximum thickness, after Polonic, 1996) with a varied lithology. The Intramoesian fault (Ploiesti-Fierbinti-Calarasi) is an active transcrustal fault. Normal (crustal) earthquakes have been produced along this tectonic line extended from Getic Nappe of South Carpathians in northwest to continental platform of Black Sea in the southeast (Cor- nea, Polonic 1979; Visarion et al., 1988; Tari et al., 1997). This seismogenic zone of Romania extended untill to the Shabla region (Bulgaria) where an earthquake with the magnitude (Mw) of 7.2 occurred in 1901 (Radulian et al., 2000). This fault also indicates an evident changing of thermal and magnetic fields. The Dobrodjean sector of the Moesian Platform is "colder", with a geothermal gradient of 1.5 0 C/100 m, in comparison with the western sector, which is "