TECTONIC GEOMORPHOLOGY ANALYSIS OF YOGYAKARTA OPAK FAULT

• Main Author: Nurmalasari, Ageng
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/69800
• Institution: Institut Teknologi Bandung

The ocean plate movement of Australia Indian is the trigger of earthquake transmission of the fault that extends from South to North and it’s located along The Opak River, so it’s called Opak Fault. One of the activity indication was the earthquake that happen on May 27th, 2006 hit Yogyakarta and Central Java. Based on data from USGS (United States Geological Survey), the center of the earthquake is on the land with magnitude Mw: 6.2, at the same time BMG recorded the sourced of the earthquake is in the sea with magnitude 5.8 of Richter Scale. The research area is located along the Opak River valley, it’s along with the damage zone of the earthquake on 2006 which happened in Opak river. The aim of the study is to determine the recording of tectonic activities are affected by Opak Fault. The method of this research is tectonic geomorphology approach for both quantitative and qualitative. Qualitative method approach is to identify morphotectonic with interpretation of landforms at 30m resolution of SRTM DEM. Besides qualitative approach, morphometric calculations using five parameters also well done, which is hypsometric curve, drainage asymmetry basin, stream length gradient index, mountain front sinousity and river flow area/DAS index. Morphometric analysis based on river flow area that delineated by topographical map scale of 1: 25,000. The result of morphometric analysis is classified into Tectonic Activity Index/IAT to determine tectonic class. The values of the index were divided into three classes to define the degree of active tectonics. There were 7 of river flow areas from 55 river flow areas such as Pleret and Patuk areas are classified into low tectonic class with value 2,5, Imogiri area is classified into high tectonic class with values 1,5 and 1,75, the southern area of Imogiri such as Panggang, Dlingo, Patuk, Prambanan and Kalasan areas are classified into moderate tectonic class with value 2 – < 2,5. The result of the index classification of Tectonic Activity Index is used to make directions for earthquake disaster mitigation. Area with the low susceptibility is located in the South of Opak Fault such as Panggang, Pundong, Imogiri, Dlingo, and Jetis, meanwhile the area in the North of Opak Fault such as Kalasan, Prambanan, Berbah, Pleret, Pinyungan and Patuk have high susceptibility of earthquake disaster.