Mapping Earthquake Level Using Probabilistic Seismic Hazard Analysis (PSHA) Method in Banjarnegara District

摘要

Indonesia is called rings of fire, because Indonesia is flanked by 3 active plates namely the Eurasian plate, the Indo-Australian plate and the Pacific plate. This resulted in Indonesia being vulnerable to geological disasters, ranging from landslides, volcanic eruptions, earthquakes and tsunamis. Java Island is one of the areas potentially affected by earthquakes including Banjarnegara Regency. Banjarnegara Regency is geographically located at coordinates 70 10 '12 "SL - 70 22' 12" SL and 1090 4 '24 "ES -1090 50' 24" ES and is an area that is close to the impact zone and has a complex geological structure because this area is surrounded by mountains and hills. Therefore an earthquake hazard level mapping study was carried out using the Probabilistic Seismic Hazard Analysis (PSHA) method in Banjarnegara Regency. The use of the intended method is to obtain the Peak Ground Acceleration (PGA) value which is used as a hazard parameter. The level of danger is based on the PGA value and the earthquake intensity value in the Modified Mercalli Intensity (MMI) scale. In this research, the geomorphological approach and microtremor analysis are carried out to quantify site specifics which are expressed in Vs30 values. Based on the research conducted, the value of Peak Ground Acceleration (PGA) in soil and bedrock is very high. PGA on bedrock has a value of 175.8942319 gal - 227.8643774 gal, while the PGA value on the soil has a value of 249.5442328 gal - 305.8190073 gal. whereas for PGA values through geomorphological modeling has a value of 53.17234277 gal - 305.8190073 gal. The high value of PGA produces a high intensity value, which is almost scattered throughout the region. The value of earthquake intensity in Banjarnegara is in the MMI V-VIII range. Thus, it can be ascertained that when an earthquake occurs in Banjarnegara, it will have a high impact on damage. So that it is necessary to conduct pre-disaster mitigation to improve the condition of the buildings to be built