RELATIONSHIP BETWEEN THE 13 MAY 1995 KOZANI-GREVENA (NW GREECE) EARTHQUAKE AND THE POLYPHYTO ARTIFICIAL LAKE

On 13 May 1995 a strong earthquake of M-s=6.6 struck the cities of Koz ani and Grevena in northwestern Greece. This region is characterized b y low seismicity. In the same area, three hydroelectric dams have been operating for the last 30 years. One of them, the Polyphyto dam, is l ocated only 40 km from the epicenter of the 13 May earthquake. In the present work all available seismological aspects of the main event, su ch as focal properties and source parameters together with foreshock a nd aftershock characteristics of the earthquake sequence are considere d in order to examine whether the water level changes behind the Polyp hyto dam induced the unusual seismic activity in this area. Thus, a de tailed examination of the seismic activity is made and this is compare d to the seismotectonic regime of the region and the reservoir loading from 1976 to 1995. The results show that there is no obvious correlat ion between seasonal or sharp fluctuations in the water level and the seismicity of the region (except once during 1989). Moreover, comparis on with other previous cases of induced seismicity in Greece and in ot her countries shows no similarities to the Kozani-Grevena earthquake s equence. It is concluded that the Kozani-Grevena earthquake is therefo re an event in the framework of the regional seismicity rather than an event triggered by the impounding of the Polyphyto artificial Lake. ( C) 1998 Elsevier Science B.V. All rights reserved.