KHESNA SEISMIC ZONE - A TEST SITE FOR SES۱MIC POTENTIAL RESEARCH

The Kresna seismic zone (SW Bulgaria) is famous with the two strong earthquakes occurred on ۴-th April ۱۹۰۴. Both shocks, in the time interval of ۲۰ minutes, (M=۷.۲ and ۷_۸) have generated big destructions of the buildings, many secondary effects such as landslides, rockfalls, mud and sand volcanoes, surface ruptures and many, many deaths and injured. The shocks have been followed by a long and strong aftershock series, due to the source depth (۳۴-۴۰ km.) and other specific peculiarities of the origin. The zone has been chosen for a test site because of the very interesting behaviour of the seismic process as well as the most active zone during the present days on the territory of Bulgaria and its location on the boundary of Bulgaria, Greece and Macedonia, It is surrounded by other separate zones with their own life and regime, placed in the near vicinity. The interactions between them is also interesting scientific and practical problem