DOREL ZUGRAVESCU 1, DUMITRU STANICA 1, MARIA STANICA 2,
DUMITRU ENESCU 3, ANDREI SOARE 2, FLORIN MUNTEANU 1
1"Sabba S. Stefanescu" Institute of Geodynamics of the Romanian
Academy
19-21 J.-L. Calderon St., Bucharest 37, R-70201, Romania
2 Geological Institute of Romania, 1 Caransebes St., RO-79678, Bucharest, Romania
3 National Institute for Earth Physics, Bucharest-Magurele, E-mail: denescu@infp.ifa.ro
The paper approaches the prognosis of the strong earthquakes by using the electromagnetic precursors, under the specific geotectonic circumstances of Vrancea zone. After a short presentation of a reliable monitoring of the electromagnetic (EM) field, its advantages comparatively with the electric field (DC method) alone are emphasized. In addition, the necessity of a differential monitoring, at least at three sites placed at a sufficient long distance, in order to eliminate the shallow effects generated by the geological features is pointed out. The results obtained in a first stage — the EM monitoring in only one site (the national Geophysical Observatory – Surlari), in order to determine the pattern (the interval of normal variations of the electromagnetic field, in terms of non-seismicity) of this area represents the main subject of this paper. Finally, several conclusions are mentioned.
Key words: electromagnetic precursors, seismic area, differential monitoring,
impedance tensor, electric resistivity, decomposition technique.