ESTIMATED STUDY OF AVERAGE DENSITY VALUE UNDER THE EARTH SURFACE USING PARASNIS, NETTLETON, AND RIKITAKE METHODS CASE STUDY: SUMANI GEOTHERMAL FIELD, SOLOK REGENCY, WEST SUMATERA

• Main Author: Putra Prasetyo, Anggara
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/53293
• Institution: Institut Teknologi Bandung

In calculating the Bouguer anomaly, the average density is an important parameter to consider. There are several methods that can be used to estimate the density, including the Nettleton and Parasnis methods. In this study, a study was conducted to understand the accuracy of the two methods and why this method is often used. In addition, a study was also conducted on another method, namely the Rikitake method as a comparison in estimating the density value. To understand this, various synthetic models were carried out by making topography and density variations. Based on the results of synthetic modeling using the Nettleton, Parasnis, and Rikitake methods, it is found that topographic variations have a greater influence than density variations. In this case, the model with a wide range of topographic variations provides good accuracy (with errors below 8%). Of the three methods, the Parasnis method has better accuracy (error 0.161% to 5.221%) compared to the Nettleton method (error 0.165% to 7.517%) and Rikitake (error 0.165% to 7.925%). Based on this, it can be concluded that both the Parasnis, Nettleton, and Rikitake methods provide almost the same density estimation results for surface geological conditions with a wide range of topographic variations. Furthermore, in this study, the calculation of the average density using the three methods above is based on gravity data in the Sumani Geothermal field, Solok Regency, West Sumatra. The calculation results from the Parasnis, Nettleton, and Rikitake methods show the average density values of 2.89 g/cc, 2.76 g/cc, and 2.88 g/cc, respectively. Based on the calculation of Bouguer anomaly and its residual anomaly using this density, it shows that the anomaly distribution pattern for the three methods is quite identical. From the three residual anomaly maps, it can also be well identified that there is a northwest-southeast trending structure that is associated with the Sumatra fault structure.