MORPHOTECTONIC AND SATELLITE IMAGERY ANALYSIS FOR IDENTIFYING QUATERNARY FAULT AT SOUTHERN PART OF CIANJUR-GARUT REGION, WEST JAVA, INDONESIA

摘要

Morphotectonic is geomorphological characteristic as response of tectonic. Watershed morphometric may reflect tectonic conditions of a region. Parameters of morphometric and morphotectonic can be an indicator of the activity of a fault. Active fault is a tectonic trace that can be a source of seismicity in the area of land. The southern part of West Java is dominated by Quaternary volcanic products. These materials are generally unstable, especially when affected by fault. Some areas in the southern part of West Java regionally controlled by Quaternary faulting. The movement of this fault can be triggered by the subduction activity in the south of Java Island. This study aims to determine the role morphotectonic characteristics as indicators of the presence of active faults in the region of the Southern part of Cianjur and Garut. The result is expected to be useful to help the community and the government in anticipation of a crisis when geological disasters occur as an impact of the active faults. Systematic research based on the mindset that past geological events, along with its development can produce a typical landforms. Lineament of the landslide zone is assumed to be associated with active fault lines that can be reflected by the specific characteristics of morphotectonic and lithology. Digital analysis of satellite imagery used to determine the distribution of lineament and landslide zones. Probabilistic approach is used in the data analysis. The study was conducted in five watersheds, i.e. Cisadea, Cipandak, Cilayu, Cikandang, and Cikaingan. The results showed that there was a tectonic control in watersheds of Cipandak , Cilayu, and Cikaingan. Meanwhile, tectonic control in the watersheds of Cisadea and Cikandang occurred in a specific location. This phenomenon is reflected by the unique shape of the three watersheds. The watersheds longitudinal direction tends to follow the direction of the main fault. Slim shapes for the three watersheds indicate tectonic control is still dominant. There is a unique phenomenon in the Cikaingan watershed, where drainage can be grouped into two patterns. Dendritic pattern in the upper and trellis pattern in the middle-downstream. It is characterized by the presence of a fault between the two patterns. The upstream blocks tend to move than the middle-lower block. Blocks that have movement tends to deform more intensive, making it unstable and easily respond to weathering and erosion processes. This resulted in many river channels formed in the northern part of the block than a southern block. This phenomenon is also shown by the results of the quantitative analysis of variables associated with morphotectonic and morphometric.