HYDROSEIMICITY - NEW EVIDENCE

Abstract

The model of hydroseismicity relates variations of the hydrological state of the earth's crust to seismicity through the weakening of rocks by fluids and the transfer of stresses from hydrologically affected regions into seismogenic regions. The model has been tested by a number of statistical analyses. One such analysis is correlating the Caspian Sea water imbalances over the years with the regional seismicity with a time delay between the two. The correlation is significantly positive if seismicity leads by up to 1a, and negative if seismicity is delayed by 3–5a relative to the water imbalance. This is interpreted by water being expelled from the crust into the lake by compressive seismic activity and with a delay by the inflow of water into the seismogenic layer from the lake. Significant seasonal variations of seismicity have been found to exist in several parts of the world. These variations also correlate with precipitation, but generally there is a delay of the seismicity by a few months. This is a plausible result if one considers that water has to flow from the source (lake bottom, earth's surface) to the seismically active depths; the delay times agree with seismogenic depths of a few kilometers to about 10 km (in the Caspian Sea area). However, there are many open questions, e.g. why there does not seem to be much correlation of the seasonal effect with the different climates.