STUDY ON THE SIGNIFICANCE OF REDUCTION TO THE EQUATOR (RTE), REDUCTION TO THE POLE (RTP), HILBERT TRANSFORM AND PSEUDOGRAVITY IN MAGNETIC DATA INTERPRETATION

• Main Author: Nailufar Rusman, Mira
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/76259
• Institution: Institut Teknologi Bandung

Geomagnetic methods play a crucial role in a wide range of applications, including structural mapping and identification of mineralized zones. However, interpreting geomagnetic anomaly data can be challenging, particularly in research areas situated at low latitudes, due to the influence of the Earth's dipole magnetic field. In this study, we investigate the significance of employing methods to transform dipole anomalies into monopoles, aiming to enhance the interpretability of the data. Four methods were examined: Reduce to Pole (RTP), Reduce to Equator (RTE), Hilbert transform, and Pseudo-Gravity. The RTP method was implemented using general equations for RTP, Pseudo-inclination (PI), and Nonlinear thresholding (NTRTP). The computation programs for RTP and RTE were developed using the Matlab programming language. Synthetic models were constructed to investigate the effects of inclination values, object dimensions, and positions on the resulting magnetic anomaly response. To quantitatively assess the performance of each method, a correlation coefficient was computed between synthetic data at a 90-degree inclination (pole) and the calculation results obtained from each method. The analysis of synthetic data with low inclinations (below 50) demonstrated the superior performance of the NTRTP method, achieving correlation coefficients ranging from 0.78-0.95. In contrast, the general equation and pseudo-inclination methods exhibited a correlation coefficient of 0.4101 at an inclination of 50, which significantly increased to 0.9933 at an inclination of 300. The RTE method also yielded favorable results, exhibiting a correlation coefficient of 0.80. However, it should be noted that qualitatively, the RTE method was less effective in eliminating the dipole effect. Qualitatively, the pseudogravity method accurately identified anomaly locations while eliminating dipole effects. On the other hand, the Hilbert Transformation method could only identify anomaly locations at an inclination of 300. The implementation was conducted utilizing magnetic data in the Gunung Pandan geothermal area. The application of the reduced to the pole (RTP) technique on the field data successfully remove the dipole effects, and make interpretation process easier. Based on RTP map, the range of anomaly values spanning from -800 nT to 1000 nT. Based on the calculation results, the RTE method and Hilbert Transformation still exhibit dipolar anomalies, thereby complicating the interpretation process. Through a comprehensive analysis of the RTP map and residual map supported by geological and additional geophysical information, the identification of several N-S oriented fault structures became feasible. Furthermore, conspicuous high anomalies were observed at the Gunung Pandan site, indicative of a probable intrusion of andesitic igneous rock. Moreover, lower anomalies were also detected in the vicinity of the Banyukuning hot springs, suggesting their potential association with the conduit path of the geothermal manifestation.