PSO AND VFSA GLOBAL OPTIMIZATION INVERSION TO HED-TDEM METHOD FOR STUDYING SUBSURFACE RESISTIVITY

• Main Author: Aji Hapsoro, Cahyo
• Format: Dissertations
• Language: Indonesia
• Subjects: Fisika
• Online Access: https://digilib.itb.ac.id/gdl/view/46359
• Institution: Institut Teknologi Bandung

The global optimization inversion was successfully applied to TDEM data for the configuration of the HED source. In the future modeling part, Hankel's transformation is used to obtain solutions in the vertical magnetic field. The transformation of the time domain is carried out using the Laplace transformation with the Gaver-Stehfest method. Non-deterministic (stochastic) investment solutions were successfully performed in this study using PSO and VFSA algorithms. Variations in the PSO parameters are also observed to determine the best adaptation value. The combination of the total number of particles and the number of iterations is obtained at an optimal value of 90 - 70 and produces a final mismatch value of 0.089 %. The convergence of inappropriate values is obtained relatively quickly and guarantees stability until it reaches the final iteration. The reverse resistivity performance curve is close to the fit of the test model. The investment of data when adding noise is also done to test the quality of the investment program. A reversal with noise data results in a mismatch value of $0,1010$ for an additional noise of 5 % and 0.537 % for an additional noise of 10 %, with the same PSO parameters as those applied to free noise data. In investment using the VFSA approach, the smallest mismatch value is 0.10 %. This value is achieved with the VFSA constant that it includes; NV = 50, maximum iteration = 250 and initial temperature T0 = 5. With respect to the data with added noise, 5 % obtained an insufficiency of 1.009 % and 2.9% for the data with added noise 10 %. The investments of PSO and VFSA also apply to the TDEM data of the observations. In these results, the resistivity value of the investment results has the same tendency of the model with the test model. The results of the investment with PSO and VFSA show the same resilience model as the Occam approach. This proves that the investment method with the PSO and VFSA approaches has been successfully applied to the data in the TDED HED configuration field for volcanic regions. The investment results show the presence of a fairly resistive top layer of approximately 80-100 ?m, followed by a conductive layer of approximately 1 - 1.5 ?m, and is terminated with a third resistive layer that It is about 200 - 240 ?m. A common feature of the resistivity profile under station UZ09 is that a fairly resistant top layer 300 - 340 ?m covers the conductive layer that is approximately 2.5 - 5 ?m above the slightly resistive layer around 50 - 60 ?m. The conductive layer represents a combination of (hydrothermally altered rocks) saturated with water and heated by hydrothermal energy, and increased conductivity values above TDEM measuring stations that can be hot gases or ionic fluids in the layer. which is rich in water.