C. CALOTA1, V. LAZARESCU1, T. MOLDOVEANU2, DOREL ZUGRAVESCU3
1Universitatea din Bucuresti, Bucuresti, Romania
2Institutul de Studii si Proiectari Hidroenergetice, Bucuresti, Romania
3Centrul de Fizica Pamantului si Seismologie,
Laboratorul de Geodinamica,
Bucuresti, Romania
(ABSTRACT)
The high fidelity local survey performed before and after the intermediate
Vrancea earthquake of August 30, 1986 (M = 6,8 – 7,0) on the Nehoiu – Basca
Rozilei Geodynamic Polygon (sited on the Median Palaeogene Tlysch nappe at
the Eastern Carpatheans Are Bend, practically within the Vrancea epicentral
zone) and on the Caldarusani-Gruiu Geodynamic Polygon (situated across the
Tinosu-Fierbinti-Calarasi fracture within the Moesian Platform, more than 100
km southward on the former polygon and separated from the Vrancea epicentres
by a distance comparable to the depth on intermediate foci) revealed significant
temporal changes in the distribution of gravity values.
The fact that no topographic level changes have occurred on these polygons,
suitable to explain the measured gravity variation and shape of its anomalies,
as well as the icting of both arreas of research over deep fractures, suggest
that either the geological sedimentary formations of the adjacent faulted blocks
have been shifled by differential compaction or they have been submitted to
a different degree of microfracturing (dilatancy) which also involved the basement.
Key words: geodynamics, geodynamic polygons, gravity variations, Vrancea earthquakes, predictive elements, intermediate earthquakes, vertical displacements