Geophysical and Geodetical Investigation of A Landslide Area (Koyulhisar-Sivas, Turkey)

Abstract. This study includes geophysical studies carried out in the last section in the close south of Koyulhisar (Sivas) landslide site. Additionally, the study area is in the most active location where landslide's displacement amount is the highest. The landslide site basically has been examined geophysics (SRT, GPR) and geodesic (GNSS) methods. According to the geophysical results, within ~ 20 m of investigation depth, layers with the average seismic P-wave velocities (V_P) of 0.30, 1.00 and 2.00 km/s have been identified. It has been understood that the thickness of the first two layers of these layers from top to the bottom is approximately 3 and 6.5 m, and the last layer with V_p > 2.0 km/s is the bedrock. Furthermore, it has been understood that the depth of the sliding surface which is the upper limit of the bedrock varies between ~ 7–10 m, there are loose units on the sliding surface, the type of sliding is planar sliding, and the direction of sliding is S–SE, the tilt of the layer has the same direction with topography, is SE-oriented and mostly bigger than 50. It was understood that the deformations in the landslide mass were occured from the geological unit, the layer or topography slope and precipitation and the landslide activity can continue in the study area. Thus, it has proven that precipitation and deformations within the layer are effective in triggering the landslide by the geodetic (IDH) observations, and it is understood that they were compatible with the geophysical results. Therefore, the study area contains the risk and the natural hazards, and these threatens the settlement area and the buldings and other constructions there.