Morphometric analysis of relative tectonic activity in the Baturagung Mountain, Central Java, Indonesia

Abstract

Special Region of Yogyakarta and Klaten district, Central Java is one of areas in Indonesia that is prone to earthquake caused by subduction in Indian Ocean and active fault in land. The earthquake sources from active fault probable from Opak and other faults located in Baturagung Mountain. Active faults controlling landform development in tectonically active regions, and it has significantly affected fluvial systems and mountain - front landscapes in the Baturagung Mountain. To assess tectonic activities in the area used quantitative analysis (morphometric). Morphometric analysis consists of 5 parameters geomorphic indices: drainage basin asymmetry (AF), hypsometric curve and integral (Hc and Hi), stream length gradient (SL) index, basin shape index (Bs), and mountain-front sinuosity (Smf). These indices were combined to yield the relative tectonic activity index (RTAI) using geographic information systems (GIS). The result found that RTAI in the study area are divided into three classes: Class 2 (high 0.6% of the watershed area (1.32 km2)); Class 3 (moderate 58.9% (122.1 km2)); and Class 4 (low 40.4% (83.75 km2)). All of morphometric analysis generally indicates this area more influenced by tectonics than erosion. The results are consistent with geomorphological observations.