The seismotechtonics characteristics of northeastern section of the Adıyaman fault zone

ABSTRACT Master Thesis THE SEISMOTECHTONICS CHARACTERISTICS OF NORTHEASTERN SECTION OF THE ADIYAMAN FAULT ZONE Ercan ZENGİN Firat University Graduate School of Natural and Applied Sciences Department of Geological Engineering 2005, Page: 90 Turkey has been found upon the most important earthquake focus of the world in terms of seismic activity. Anatolia plate is limited by the East Anatolian Fault System (EAFS) which is one of the most significant continent-interior active transform faults, the North Anatolian Fault System (NAFS) cutting diagonally the north part of Anatolian plate, and girdled by the East and Southeast Anatolia. With the discharge of seismic energy emerged by means of the earthquakes happened occasionally, tens of thousands of people in Turkey have lost their lives to earthquake disaster due to this tectonic structure group. It is also led to the economic loses seriously. Therefore, the increasing of the limited scientific studies with the seismotectonics purpose conducted in the region has been required quickly for minimizing of these earthquake disasters. This study aims realise of the earthquake producing potential by the pathway of understanding of seismic activities occurring in the past and current seismic activities of AFZ on the EAFS. Mapping studies is done to take information on the earthquakes happened in developing zones inside fault system and their focus solutions. This information has been considered important for about 6 million people living in the region especially as well as the project studies of the long-term engineering structures (i.e., bridge, viaduct, highway, dam and hospital). With this aspect, this study includes the final results of the first seismotectonics studies performed in the region. According to the results of kinematic analysis made up of the measures taken from the locations predetermined along fault zone in the scope of study, the Adıyaman Fault Zone (AFZ) is remained under the effect of different strain systems until from its first formation to its end moment. Accordingly, the availability of 5 different zones in the region is determined IXessentially in the results of kinematics studies at fault zone. From the kinematics data, some conclusions can be drawn as follows; (i) extension in head Miocene of the EAFS that also contains the AFZ occurs with tectonic regime, (ii) compression being affected at the end of mid- up Miocene is influenced by the tectonic regime, and (iii) Plio-Quaternary is characterised by the strike slip in the past and even now. When the results of both the earthquake focus mechanism and kinematics analysis made by using data obtained from the term recording with apparatus in the region are compared to each other, stress situation in terms of Plio-Quaternary is shown suitability. In the studies made by seismologic and geological data, the presence of bloc rotations between fault zones inside the EAFS is also determined. The closest example in terms of time to this phenomenon is the Sivrice earthquake happened in 2004. The seismotectonics parameters are calculated by using the results of the earthquake analysis. Occurrence probability and return period and magnitude of the largest earthquake to be taken place on fault zone using these parameters are calculated. Hence, the biggest earthquake magnitude possible to be happened in district is estimated as a Ms value between 6.5 and 6.8. Geological field studies done in the northeast section of the AFZ including one of the sub-zones of the EAFS have shown to be 5 different faults and fault sets as follows; (1) Işıktepe Fault Set (IFS) which is in the same trending with the AFZ main breaking, and an about 13 km wide sinistral strike slip fault; (2) Başkaynak Fault Set (BFS) which is a general trending of N20°E (K20°D) and able to watched until 11km; (3) Üçdeğirmenler Fault (UF) which is a general trending of east-west and 8 km wide sinistral strike slip fault; (4) Çakıroğlu Fault (CF), and (5) Gökçepelit Fault Set (GPF). Keywords: Adıyaman fault zone, EAFS, seismotectonics, focal mechanism, kinematic analysis, seismic risk