Macroscopic seismic anomalies and submarine pockmarks in the Corinth-Patras rift, Greece

Prior to the Aigion earthquake (M 6.2) of 15 June 1995 in the western Gulf of Corinth, people in the area observed anomalous phenomena, including bubb ling of the sea, extraordinary behavior of animals, earthquake lights, grou nd deformation, and the sound of wind immediately before the shock. Some pr ecursory phenomena of this kind might be understood as symptoms of gas vent ing before an earthquake. Sonar observations made in 1988 showed a chain of submarine pockmarks tracing the Aigion Fault and evidently produced by the expulsion of fluids under pressure. T. Hasiotis et al. [Mar. Geol. 130, 33 3-344] reported that hot gas erupted from a field of giant submarine pockma rks in the neighboring Bay of Patras several hours prior to an earthquake i n 1993. Automated monitoring of bottom water temperature in submarine pockm ark fields may detect outgassing events prior to earthquakes in this region . (C) 1999 Elsevier Science B.V. All rights reserved.