This project is pertinent to the understanding of the mechanism and the prediction of major geophysical events such earthquakes by using don measurements. The objectives of this work is to define optimal methodologies for earthquakes precursors studies, in term of instruments site selection and data analysis. At any given point on the Earth's surface, the temporal variation of radon concentration depends on several factors such as meteorological (e.g. temperature, pressure, rain fall, ...) and geological conditions (Radium concentration in the rocks, grain size porosity, tectonic activity, ...). A statistical study was undertaken in order to discriminate the influences of meteorological conditions and seismic events on the measured temporal variations of radon emission levels. The former are different at each site and depends on the surface geological conditions in the vicinity of the sensors; their type and shape can be identified and the remaining important variations in radon concentration may be correlated with tectonic activity. Objective criteria are needed to distinguish instrumental artifacts from real radon anomalies that reflect changes in stress and in geological conditions. However, to be useful as a precursor in an earthquake prediction program, the continuous monitoring of radon in soil gas (as well other environmental parameters) at several sites in a grid pattern is necessary. Some significant radon anomalies have been identified. The maximum of these signals have been observed precede seismic events with magnitudes 46, by four days. The short period of observations does not allow a sound reappraisal of the method for earthquake prediction, but the results certainly appear to be encouraging.
Funding SchemeEAW - Exploratory awards
153 42 Athens