Present-day seismicity and seismotectonics of the Cilician Basin; eastern Mediterranean region of Turkey

The nature of the interaction between the Anatolian, Arabian, and African plates is an important problem of northeastern Mediterranean tectonics. The Dead Sea Fault and East Anatolian Fault Zone are the most prominent structural elements in this region. The Cilician Basin, which is located at the junction of these faults, is known to have a very active seismic history. However, instrumental observations have been insufficient because of the lack of an adequate local seismic network. To monitor ongoing seismic activity and to analyze the seismotectonics of the Cilician region (36 degrees to 38 degrees N, 34 degrees to 38 degrees E), a digital seismic network of 18 stations with velocity transducers has been operated by the Earth and Marine Sciences Research Institute (EMSRI) of the Scientific and Technical Research Council of Turkey (TUBITAK) since 1993. No previous studies have been carried out in this region for crustal structure. An optimum 1D velocity model was obtained by using the VELEST algorithm for reliable determination of earthquake hypocenter locations. Approximately 2500 earthquakes detected between 1993 and 2002 with local magnitude greater than 1.5 have been located by using this optimum velocity model. The most notable feature of the epicentral distribution is the presence of dense clusters of activity along local fault trends. The majority of hypocentral depths of the events range between 5 and 35 km. Single-fault plane solutions of reliable events were calculated in order to analyze the seismotectonic characteristics of the region. Results show that the Cilicia region constitutes a wide left lateral shearing zone that indicates a diffuse plate boundary between the African, Arabian and Anatolian Plates.