INSTABILITY OF THE GROUND WATER-GAS SYSTEM OF THE PRUT FAULT ZONE AND ITS RESPONSE TO THE VRANCEA EARTHQUAKE OF AUGUST 31, 1986

Abstract

The authors have demonstrated that water-gas systems filling fault structures of seismically active regions are chemically and even isotopically unstable, not only in the period of accumulation and relaxation of elastic strain in the focal zones of tectonically-induced earthquakes, but even in aseismic periods. But these previous investigations were carried out primarily in the geodynamically active Central Asian and Caucasus regions. There is also a small amount of evidence indicating chemical and carbon-isotope instability of the gas component in subsurface water-gas systems of aseismic zones of the Kola Peninsula and the Lower Volga region They seem to indicate that the geography and geodynamics of this effect are of considerably greater extent than was previously thought. The present paper deals with chemical and carbon-isotope stabilities of gases in subsurface water-gas systems of the Prut first-order fault structure and the response of certain of their characteristics to the preparation and occurrence of the Vrances earthquake of August 31, 1986.