Index active tectonic relative of Karangsambung geopark area, Central Java, Indonesia: assessment for developing geological disaster-based areas

Abstract

Abstract Karangsambung as a “subduction fossil” of the Cretaceous-Paleocene on the island of Java, has a complex geological structure. The current subduction process in the south of Java with a north-south compression force has contributed to the reactivation of the geological structure in Karangsambung. The index active tectonic relative (IAT) of the Karangsambung area reflects the current level of tectonic activity. IAT is obtained from quantitative calculations of geomorphic indices, including streams length - gradients index (Sl), the ratio of valley floor width to valley height (Vf), basin asymmetry (Af), basin shape (Bs). mountain front sinuosity (Smf), the hypsometric integral (HI), and drainage density (Dd). The index active tectonic relative (IAT) calculation with an average IAT value of 2.37 indicates that tectonic activity is in the medium/moderate category. In addition, an attempt was made to compare the regional neotectonic activity with the relative tectonic activity of the study area. Based on this geomorphic analysis, the study area may have a lower seismic risk but needs to be evaluated more carefully for regional seismic hazards. The IAT value can be used as an initial reference for geological disaster assessment, especially earthquakes hazard in the development of the Karangsambung National Geopark Area.