Relationship between the 13 May 1995 Kozani-Grevena (NW Greece) earthquake and the Polyphyto artificial lake

摘要

On 13 May 1995 a strong earthquake of M_s = 6.6 struck the cities of Kozani and Grevena in northwestern Greece. This region is characterized by low seismicity. In the same area, three hydroelectric dams have been operating for the last 30 years. One of them, the Polyphyto dam, is located only 40 km from the epicenter of the 13 May earthquake.In the present work all available seismological aspects of the main event, such as focal properties and source parameters together with foreshock and aftershock characteristics of the earthquake sequence are considered in order to examine whether the water level changes behind the Polyphyto dam induced the unusual seismic activity in this area. Thus, a detailed examination of the seismic activity is made and this is compared to the seismotectonic regime of the region and the reservoir loading from 1976 to 1995. The results show that there is no obvious correlation between seasonal or sharp fluctuations in the water level and the seismicity of the region (except once during 1989). Moreover, comparison with other previous cases of induced seismicity in Greece and in other countries shows no similarities to the Kozani-Grevena earthquake sequence.It is concluded that the Kozani-Grevena earthquake is therefore an event in the framework of the regional seismicity rather than an event triggered by the impounding of the Polyphyto artificial Lake.