Global Inversion of Grounded Electric Source Time-domain Electromagnetic Data Using Particle Swarm Optimization

Global optimization inversion of grounded wire time-domain electromagnetic (TDEM) data was implemented through application of the particle swarm optimization (PSO) algorithm. This probabilistic approach is an alternative to the widely used deterministic local-optimization approach. In the PSO algorithm, each particle that constitutes the swarm epitomizes a probable geophysical model comprised by subsurface resistivity values at several layers and layer thicknesses. The forward formulation of the TDEM problem for calculating the vertical component of the induced magnetic field is first expressed in the Laplace domain. Transformation of the magnetic field from the Laplace domain into the time domain is performed by applying the Gaver-Stehfest numerical method. The implementation of PSO inversion to the TDEM problem is straightforward. It only requires adjustment of a few inversion parameters such as inertia, acceleration coefficients and numbers of iteration and particles. The PSO inversion scheme was tested on synthetic noise-free data and noisy synthetic data as well as to field data recorded in a volcanic-geothermal area. The results suggest that the PSO inversion scheme can effectively solve the TDEM 1D stratified earth problem.

Identification of Sediment Formation Based on Magnetic Content and Element Composition of Mud Volcano in Sangiran Sediment using VSM and X-Ray Fluorescence

Based on trace geological history and several studies, the Sangiran mud volcano provides insight into the geology and hydrology of the region, aquifer system in the basin, groundwater flow patterns and characteristics, rock lithology, hydrogeology condition, and saltwater trap mapping. Related to these conditions, studies were conducted on the magnetic content and composition of the major oxide compounds in the Sangiran sediments. Sample analysis was based on geochemical methods. The methods consist of frequency dependent magnetic susceptibility and vibrating sample magnetometer (VSM) analysis. Geochemical analyses using x-ray fluorescence (XRF) analysis have been conducted and various elemental grades have been determined. VSM results confirm that the magnetic content of Sangiran sediments is partly dominated by Fe (17.66 percent) contained in hematite (Fe2O3). At the same time, the samples of Sangiran sediment were enriched by Si, Fe, Al, Ca, Cl, Ti, and K according to XRF measurements. The samples exhibited the highest Si and Fe concentrations in samples T1 (Si is 29.48 percent and Fe is 13.66 percent) and T7 (Si is 24.95 percent and Fe is 12.01 percent). Meanwhile, in the T4 sample, the highest concentrations were Si and Ca, 23.45 percent and 13.45 percent, respectively. Retrieved from the magnetic susceptibility measurement, this paper confirm that Fe content is one of the components of volcanic ash in the Sangiran sediment.DOI: 10.17977/um024v8i12023p00

Rare earth element characterization of Bledug Kuwu Mud Volcano, Central Java, Indonesia, based on geochemical analyzes (Susceptibility, XRF, XRD, SEM-EDS and ICP-EOS)

Mud volcano material is generally rich in oxides, while oxides are the main compounds forming rare earth elements. Bledug Kuwu, Central Java, Indonesia, is one of the active mud volcanoes, so there may be rare earth elements. This research is the characterization of rare earth elements (REE) in the Bledug Kuwu mud using magnetic and geochemical methods. Magnetic characterization uses magnetic susceptibility measurements. The geochemical characterization of the mud samples consisted of the XRF (X-Ray Fluorescence), XRD (X-Ray Diffraction), ICP-EOS (inductively coupled plasma) test, and the SEM-EDS (Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy) test. The results of the geochemical analysis of the Bledug Kuwu mud sample were the content of quartz, kaolinite, and calcite with an average concentration of 42.26%, 23.67%, and 33.96%. The susceptibility of Kuwu’s mud is 0 because the concentration of metal elements is low; according to the results of XRF, XRD, and SEM tests identified the main mud elements as C, O, Si, Ca, and Al. The rare earth elements in Kuwu’s mud are Ce, Dy, Eu, Gd, Ho, La, Nd, Pr, Sm, Tb, Y, and Sc. The highest concentrations were Ce 52.22 ppm and La 47.95 ppm

Identification of Mud volcano’s structure using gravity satellite and fault fracture density analysis: case study Ciuyah Mud Volcano, Kuningan, West Java

Mud volcanoes, known as mud extrusion phenomenon, is a geological feature that expels suspended fine-grained sedimentary materials and fluids to the surface due to buoyancy and pressure difference. This geological feature is found almost all over the world and formed in compressional tectonic environments, one of which is the Ciuyah Mud Volcano, Kuningan, Indonesia. Previous studies have shown that the appearance of the mud volcano was influenced by tectonic activity that formed a ‘hypothetical’ fault structure as a pathway for mud migration and extrusion to the surface. Integration of geophysical studies using satellite gravity and geology using fault fracture density analysis was conducted to prove the existence of the ‘hypothetical’ fault structure. The results show that the mud volcano site is located in a low to high gravity anomaly pattern associated with significant density contrast differentiation followed by the maximum value of FHD and low-high SVD pattern oriented west southwest - east northeast (WSW - ENE). The gravity anomaly pattern can be associated with the presence of faults. This is reinforced by the fault fracture density map which shows that the mud volcano site is located in a medium to high fracture density zone (weak zone) associated with good permeability conditions below the surface. Thus, the research results have proven the existence of a ‘hypothetical’ fault as the migration and extrusion pathway of Ciuyah Mud Volcano mud that has been studied previously

Magnetic Signature and Element Content of Upflow and Outflow Hotspring in Arjuno–Welirang Geothermal System

Research on magnetic properties and chemical element content of environmental deposits has been conducted for various purposes. This study focuses on characteristic magnetic susceptibility, magnetic mineral morphology, and the elemental composition of Cangar and Padusan hot springs in the Arjuno-Welirang geothermal system to differentiate upflow and outflow systems, respectively. The measurements were performed for better understand the relation between magnetic susceptibility, Fe-Silicate content, magnetic mineral morphology, surface temperature and compare these characteristics in two kinds of hot springs in the same mountain system. Magnetic susceptibility ranged (7.558 - 62.694 ) × 10-6 m3/kg with an average of 30.651 × 10-6 m3/kg for Cangar (upflow) and (11.821 - 28.101) × 10-6 m3/kg with an average of 18.148 × 10-6 m3/kg for Padusan (outflow). In situ magnetic minerals extracted of hot springs are averaged of magnetic susceptibility is 26.981 × 10-6 m3/kg for Cangar and 24.445 × 10-6 m3/kg for Padusan. The element content dominated by Al, Si, K, Ca, Ti and Fe, where Fe is more abundant in Cangar as an upflow. The higher magnetic susceptibility, the greater of Fe-silicate content in both of hot springs. The surface temperature ranged from 38 - 48°C, where the higher temperature, the magnetic susceptibility increased. In Cangar, extracted magnetic minerals tend show crystalline, especially hedralic shape with very fine surface, clean and free of impurities. Meanwhile, some magnetic minerals are also found in spherical shapes, especially in Padusan