PROFOUND CHANGES IN THE CHEMICAL COMPOSITION OF NATURAL GASES OF KIRGHIZIA PRIOR TO SEISMIC EVENTS

Abstract

The gas component of groundwater-gas systems is the most mobile component of subsurface fluids, and responds actively to geodynamic phenomena. It has been demonstrated that anomalous behavior of the chemistry and isotopic makeup of the gases sometimes foreshadows large earthquakes. An investigation of variations in the chemical composition of groundwater-gas systems during the period before the Gazli earthquakes of 1976 and 1984 indicates that it became locally unstable, over an immense area of the Turanian Plate and its fringing mountain structures, from the Kyzylkum Desert to eastern Ferghana and from the Kopetdag Range to the Tashkent Artesian Basin. Each earthquake was preceded first by a decline in the relative CO2 concentration followed by an abrupt, brief rise, each successive stabilization in the CO2 concentration was disrupted by a strong earthquake. The data indicate that present-day geodynamic processes in seismically active regions that are ultimately manifested as strong and frequent earthquakes are accompanied by major alternations in the gas chemistry of groundwater-gas systems, the direction of such alterations being a reflection of particular trends in the tectonic activation of the region.