Earthquake Belts in Central and Eastern Europe. Some Seismotectonic Aspects

Abstract

The distribution of earthquake foci in the crust and the upper mantle indicates the position of mobile zones whereas the distribution of the released seismic energy in time gives evidence about the intensity of movements or in other terms about the released stress. We attempted to define some general seismotectonic conclusions about the region of Central and Eastern Europe which is marked by very differing levels of earthquake activity. For this purpose the available seisraological and tectonic data bases were used. Epicentre maps demonstrating the general pattern of earthquake distribution on this territory Schenkové et al. 1979) help to define earthquake belts and the level of their activity. Some belts are very conspicuous, some are uncertain. Combining the epicentre maps (a)< 1900, b) 1901–1972) we can define several earthquake belts in Central and Eastern Europe with different level of shallow seismic activity. There is only one zone, the Vrancea zone, of intermediate depth activity in the investigated area. Neotectonic information was taken mainly from the following sources : Tectonic map of Europe (ed. Schatsky 1962), Tectonics of the Carpathian-Balkan regions (ed. Mahel 1974), national maps and data on recent movements in Central and Eastern Europe, deep faults resulting from gravimetric and seismic surveys (Dobrev and Shchukin 1974, Sollogub et al. 1978). Lineaments of the first order and regional faults separating large units, proved by seismic or gravimetric surveys, were plotted into the seismotectonic scheme (Fig. 1.) together with the largest observed events (M≥5 1/2 or I o ≥8 1/2° MSK). Analyzing all available information some conclusions can be made : 1 There is a different degree of correlation between earthquake foci and fault zones. For instance the Peripienian lineament shows a large earthquake activity along its western branch, whereas the crustal activity is vanishing in the Eastern Carpathians. An example of a good correlation are the Struma, Marica, Yambol and Central-Rhodope faults. The lineament of the first order, the Vardar fault zone, has been active only in some sections. An interesting problem is posed by the assumed connection between the Vardar and Elbe lineaments (Bonćev 1965). The Tornquist—Teisseyre lineament is without any recent earthquake events. 2 There are regions where the earthquake pattern indicates lines which are transversally aligned as compared with the general trend of geological formations, one extending from the Skadar Lake in the NE direction to Bulgaria or the Raab line, which seems to extend farther to the SW forming a transversal earthquake belt. 3 The most difficult task is to find relations in the Pannonian basin, where also large events originated in the past. One possible interpretation of this activity can be explained by the crossing of the Vardar-Elbe lineaments with the Periadriatic line. The above seismotectonic correlations are also made for estimating zones which have not been recently active but may have a long-term earthquake generating potential. The study continues.