STUDY OF THE INFLUENCE OF REDUCED TO THE POLE, REDUCED TO THE EQUATOR, AND HILBERT TRANSFORMATION ON GEOMAGNETIC DATA MODELLING

• Main Author: Firmansyah, Fichri
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/76449
• Institution: Institut Teknologi Bandung

The geomagnetic method can be used for regional exploration to meet the needs of natural resources, such as geothermal. The geomagnetic anomaly is dipole in nature, so the interpretation of the body anomaly becomes more difficult. Therefore, a filter is needed to convert geomagnetic data into a monopole. In this study, filters are used in the form of reduced to the pole (RTP), reduced to the equator (RTE), and Hilbert transformation. Several synthetic models are used to study the effect of the filter in the body anomaly interpretation process. Then, field data is also used to strengthen the conclusions that have been obtained from synthetic data. Synthetic data variations are made based on differences in dimensions, location, depth, and inclination. The filtering results in this study were observed qualitatively from the anomaly patterns in the model and quantitatively from the average percentage of accuracy of the actual number of anomalies and the distance between the highest point (RTP and Hilbert) or lowest (RTE) to the center of the actual body anomaly. Qualitatively, RTP is the best filter based on the anomalous patterns seen in each model. Quantitatively, RTP is also the best filter with the smallest distance from the peak anomaly to the center of the anomaly body and the highest average percentage of accuracy of the number of anomalies, namely 87%. RTE has analysis results that are not as good as RTP. This can be seen from the case of two anomalous bodies which are close together and cannot be identified from the RTE filtering results, while the RTP is able to identify them clearly. Quantitatively, RTE has an average percentage of accuracy of the number of anomalies is 79.34%. Meanwhile, the Hilbert transformation is limited to the inclination angle and tends to be suitable for geomagnetic data that has an inclination angle close to 45o. The Hilbert transform has an average percentage of accuracy of the number of anomalies is 83.34%. In field data that has a low inclination angle (-31.319o) and low latitude (-7.33528o), it can be seen that all filters tend to be used effectively, but the RTP tends to be better because it has the greatest magnetic intensity contrast. Then, indications of anomaly locations were detected in the area range 588000 – 588500 UTM X and 9175000 – 9176000 UTM Y, in the form of geothermal system anomalies.