Geomorphological Features and Seismicity of Bigadiç Plain and its Immediate Vicinity

Abstract

Bigadiç plain is located in the southeast of Balıkesir, in the south of the Marmara region. The purpose of this study is to determine the geomorphological and seismic features of this plain and its immediate vicinity. To that end, geologic and topographic maps of the area were examined, and information on the processes of geomorphological configuration was obtained. In the meantime, an outline geomorphological map was generated. In addition, earthquakes and their effects on the area were gathered. Field studies were conducted in different time periods; information collected in the field. Data obtained from different sources were integrated, and the results were found. Miocene and Pliocene era volcanic formations have an important effect in the formation of Bigadiç basin. Alluvium belonging to the Quaternary era is the youngest geologic formation in the area. Rivers with parallel and sub parallel dendritic drainage patterns take their sources from high areas in the west and the east of Bigadiç plain, and flow towards Simav stream. These rivers lie along the east-west direction. Faultlines are located along the SE-NW direction, and the study area is seismotectonically situated between the North Anatolian Fault Zone and the Aegean Graben System. Some faults in the area intersect the Pliocene formations. The presence of epigenetic gorges and terraces at different elevations indicates that the area is topographically young and has a polycyclic structure. Bigadiç plain and its immediate vicinity have the characteristics of a tectonic basin and have substantially undergone faulting. This is an outgrowth of the fact that these areas are under the threat of devastating earthquakes. Bigadiç plain and its vicinity have suffered 27 large scale earthquakes in last two millenniums.