Modeling of semarang fault zone using gravity method

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A research has been conducted that aims to model the subsurface structure of Semarang Fault, Central Java using gravity method. In this study successfully measured 152 points of measurement of the earth’s gravitational field spread almost evenly in the research area. The measured data were then corrected to obtain a complete Bouguer anomaly value (CBA). CBA data is then performed upward continuation to obtain residual anomaly and local anomaly values. The CBA data local components then can be done gradient analysis using first horizontal gradient. From the results of the method is then correlated with the geological map (overlay) to the location of the Semarang Fault was estimated. CBA local component data then made 3D modeling with inversion method. From the result of first horizontal gradient analysis, it is found that the research area is separated by the weak zone of the east-west. The presence of the northern weak zone is estimated to be lithology contact between the Damar Formation and Alluvium Deposition, while the weak zone in the center of the study area is estimated as Semarang Fault. From 3D modeling which is estimated as the geological structure in the west part of the area and north-south trending direction is Kaligarang Fault with a depth of 2500 m. Semarang Fault is located in the middle of the research area on the east of the relative direction of the south of the north then curved to the west with a depth of 4000 m.