Geomorphic signature of active tectonics in Simav Graben: An evaluation of indicator relative tectonic activity of Simav Fault and its seismotectonic implications for Western Anatolia

Abstract

The main objective of this study is to analyze geomorphic landforms and quantitatively measure various geomorphic parameters to investigate the relative tectonic activity, vertical slip rate, and uplift rate of the Simav Fault. The Simav Fault, which is similar to 25 km long and morphologically composed of five mountain fronts forms the NW section of the similar to 400 km long Afyon-Simav Fault System (ASFS) within the Western Anatolian Graben System (WAGS). The mountain front sinuosity (Smf) and valley floor width-to-height ratio (Vf) hypsometric integral (HI) and hypsometric curve (HC), asymmetry factor (AF), drainage basin shape (Bs) and stream length gradient index (SL) indices were calculated to determine the relative tectonic activity in the mountain fronts and drainage areas bounded by the Simav Fault. The spatial distribution of the index of relative tectonic activity (Iat) was revealed using the combination of the obtained morphometric analysis results. Geomorphic indices indicated that high tectonic activity is intensified along the entire Simav Fault, which has a normal fault component, whereas medium and low tectonic activity is calculated on faults with strike-slip components. The highest vertical slip rates obtained using the slopes of the facets were calculated as 0.19 mm/y for MF-2 and MF-4 and the lowest as 0.07 mm/y for MF-5. Furthermore, using the heights of the facets and vertical slip rates, the youngest mountain front was found to be MF-2 (8.17 ma) and the oldest mountain front was found to be MF-5 (14.71 ma). The obtained vertical slip rate and age data showed that the mountain front in the central part of the Simav Fault is younger with having higher vertical slip rate. According to this study, the Simav Fault has played a decisive role in the evolvement of the actual morphology in the study area, has produced moderate earthquakes in the last century, and is thought to have the potential to produce larger earthquakes in the future (up to M6.71). It is important for the region to investigate and reveal the earthquake potential of this fault through paleoseismic studies.