STUDY OF TIME-LAPSE MICROGRAVITY MODELLING FROM DENSITY REDISTRIBUTION USING ELEVATION MEASUREMENT DATA USING GEODETIC GPS IN THE REGION OF BANDUNG

• Main Author: Harits Hafidza, Muhammad
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/42146
• Institution: Institut Teknologi Bandung

Land subsidence is a geological phenomenon where the decrease in elevation occurs in an area where this phenomenon can cause various disasters which can ultimately cause economic losses and become a threat to human life. Bandung is one of the cities in Indonesia that is experiencing this phenomenon. Based on the results of the average annual subsidence rate, the Cimahi area has the largest subsidence rate per year, which is -0,185 meters / year. In this study, a time-lapse microgravity (TLM) method was applied to find out how much the gravity response caused by subsidence to the observed TLM value. To get the gravitational response caused by subsidence, a program was prepared to calculate its gravitational response by performing a forward modeling calculation using the body approach of the quadrilateral prism where the final results of the modeling will be compared with the observed TLM map. The program is carried out a trial using synthetic data to test the success of the program. Based on the trials conducted, the program has succeeded in calculating the gravitational response due to subsidence. The gravity response due to subsidence in 2016-2010 in the Bandung area shows the largest TLM value in the Cimahi and Baleendah areas, around 60 µGal and shows a gravity anomaly of -0.85 µGal / cm. The results of the comparison between the observed TLM map and the calculated TLM map in the city of Bandung indicate that the effect of the gravity response due to subsidence is quite small which indicates the presence of other factors that influence the observed TLM value. These factors can be in the form of changes in buildings and changes in groundwater level (GWL). The results of the analysis of these two factors indicate that the influence of the gravitational response caused by changes in buildings is quite small and the effect of the gravitational response caused by changes in groundwater level is predicted to be quite significant to the observed TLM value.