2D MODELLING AND INTERPRETATION OF GRAVITY DATA TO ESTIMATE THE GEOMETRY OF THE BASEMENT AND THE STRUCTURE OF THE SUBSURFACE IN THE BANDUNG BASIN

• Main Author: Zulhendra
• Format: Theses
• Language: Indonesia
• Subjects: Fisika
• Online Access: https://digilib.itb.ac.id/gdl/view/47551
• Institution: Institut Teknologi Bandung

Geophysical research on the gravity method has been carried out in the Bandung Basin area. This study attempts to delineate the subsurface structure of the basin using integrated interpretation techniques on gravity data and to apply Abdeslem formulation to estimate the geometry of the basement in the basin. Spectral analysis was used to deliniate the regional and the residual components of the Bouguer anomaly. Bandpass filter was applied in order to separate the residual from the regional anomalies. The polynomial regression quadratic method is also applied to separate the regional and the residual anomalies. Five methods were used for estimating source depths and contact location: horizontal gradient, first vertical derivative, second vertical derivative, analytic signal, and euler deconvolution. Furthermore, 2D forward modeling and Levenberg-Marquardt inversion was carried out on gravity data. the Forward modeling calculates the gravity anomalies caused by a 2D source body with an assumed depth-dependent density contrast given by polynomial. The Integral of the Abdeslem formulation was solved numerically using the Gauss-Legendre Quadrature five-point rule method. The Levenberg-Marquardt inversion program can invert gravity data to infer the geometry of the source body given by the Fourier series. Some variations in the number of Fourier series were applied and it was found that the greater number of series can reduce misfit, especially in synthetic data that has noise. After being validated the inversion program was applied to the gravity data of the Bandung Basin. The inversion results suggest that the geological structure of the Bandung Basin accomodates about 1 km up to 3 km of the sediments with basements which were in located the southeast and dips to the northwest. And this result was compatible with the depth of the anomalous source using euler deconvolution with the depth and contact location details seen in the horizontal gradient cross section, first vertical derivative, second vertical derivative, and analytic signal.