MORPHOTECTONIC AND SEISMIC HAZARD ANALYSIS OF BARIBIS FAULT IN UJUNGJAYA AND SURROUNDING AREA, SUMEDANG DISTRICT, WEST JAVA

• Main Author: Humanis Brilian, Ciria
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/44145
• Institution: Institut Teknologi Bandung

The Baribis Fault is one of the faults that suspected to be active in Indonesia with a reverse movement which extending from Majalengka to Subang and suspected even to Jakarta. Baribis Fault is the northern part of back arc imbrication in West Java. The existence of several earthquake occurrences in the past 30 years along the Baribis Fault is the indication of the Baribis Fault activity. The Baribis Fault is located in West Java, which has high population density in Indonesia. Therefore, the research about activity and seismic hazard of Baribis Fault is needed to do to reduce the negative impact. The aims of this research are identifying the Baribis Fault segment in the Ujungjaya and surrounding areas, Sumedang Regency, West Java, analyzing the activity of the Baribis Fault segment in the Ujungjaya and surrounding areas, Sumedang Regency, West Java based on morphotectonic analysis, and calculating the earthquake moment generated in research regions and earthquake hazards generated in study area. The object of this research is the Baribis Fault that extends in the Ujungjaya area of Sumedang and surrounding areas of West Java Province. The data that used in this study is DEMNAS data with ± 8 meters resolution. This research covers three main steps. The first step was determining the Baribis Fault segment in the area of research that is suspected to be active. Determination of active fault is fault identification using a geomorphological approach including morphological analysis, lineament density, and knickpoints identification. Active fault analysis was carried out by doing morphometric analysis for active fault indication such as curves and integral hipsometry (HI), ratio of valley floor width and valley height (Vf) and river flow length gradient index (SL) and proven by field evidences of active fault. The second step was the calculation of the moment magnitude maximum of a predetermined active fault. Calculation of the maximum magnitude moment is based on the equation with the surface rupture length (SRL) fault parameter. The last step was seismic hazard analysis to estimate the level of ground shaking (ground motion) due to the earthquake produced by this fault using a deterministic method with the attenuation function. There are three GMPE (Ground Motion Prediction Equation) equations were used to estimate the level of ground shaking due to earthquake with magnitude, distance from the source to the observation location, and type and condition of earthquake source parameters. The equation was applied using the Openquake Engine software released by the Global Earthquake Model (GEM). The output of this analysis is the horizontal and vertical acceleration of the bedrock during an earthquake (Peak Ground Acceleration/PGA). From these outputs, may provide support and recommendation in infrastructure and area development around the active fault. Based on morphotectonic analysis accompanied by field evidence, the Baribis Fault segment in the study area is an active fault with a segment length of 20.06 km and can be an earthquake source in the study area. The moment magnitude maximum that can be released from the fault is 6.6 Magnitude. PGA values in the study area ranged from 0.107 g to 0.468 g. The highest PGA value is in southern part of the fault segment, this is due to the dip direction of fault plane that causes hypocenter is in the southern of the fault segment. Southern part of the fault section has the highest risk of shock in event of an earthquake, so it must be considered in infrastructure and area development of the surrounding area.