New data on seismicity of the middle Caspian Basin and their possible tectonic interpretation

Short-term (three months) bottom seismic observations in the area of the Yalam-Samur structure in the Middle Caspian Basin revealed a deep-seated compact zone of mantle-earthquake sources that dips beneath the southeastern Caucasus. To a first approximation, this zone may be interpreted as a seismofocal layer that characterizes thrusting of the Turan Plate under the southeastern Caucasus. However, the obtained spatial distribution of sources of microearthquakes and weak earthquakes is insufficiently reliable owing to the low aperture of the observation network of bottom seismographs. More reliable data on the position and parameters of the seismofocal layer could be obtained by the observation network with a wider spread of bottom seismographs (up to 50–100 km). If this result is confirmed, the current concept of interaction between the Alpine structures of the southeastern Caucasus, Turan, and South Caspian plates should probably be revised. The geotectonics of the Caucasus is preliminarily analyzed in the light of the newly revealed relationships.