Silvia Jannatul Fajar | Institut Teknologi Bandung (original) (raw)
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Papers by Silvia Jannatul Fajar
Frontiers in Earth Science
Among the 19 segments of the Great Sumatran Fault (GSF), the Sianok segment is unique due to its ... more Among the 19 segments of the Great Sumatran Fault (GSF), the Sianok segment is unique due to its proximity to active volcanoes as well as to the sizable Maninjau Caldera. Located next to the Sumani to its southeast, the Sianok segment also passes through a relatively densely populated area. To identify potential disasters in the future, it is imperative to understand the subsurface structures of the Sianok segment. In this study, ground magnetic measurements were conducted, and the data were combined with the Bouguer anomaly map. Hand samples were also collected and measured for magnetic susceptibility and density. The values were later used as initial parameters for modeling. Joint forward modeling of magnetic and gravity was then used in the modeling stage as well as in the interpretation stage. Subsurface models of 20 km in depth were then formulated based on the magnetic and gravity data. The models show shallow magma chambers beneath Maninjau Caldera, Mount Marapi, and Mount Si...
IOP Conference Series: Earth and Environmental Science, 2021
Ironsand deposits might contain Fe as well as other valuable elements and minerals that could be ... more Ironsand deposits might contain Fe as well as other valuable elements and minerals that could be used in a variety of applications. Often, high Fe content deposits are preferable for exploration. An earlier study shows that the highest Fe content is found in the very fine sand (VFS) size. In this study, seven VFS samples from Anoi Itam were subjected to magnetic measurements as well as X-Ray florescence (XRF), X-Ray diffraction (XRD), and correlation analyses to investigate further characteristics and how magnetic susceptibility correlates with the elemental composition of ironsand. Magnetic susceptibility varies from 2207.77 × 10-8 m3 kg-1 to 4476.68 × 10-8 m3 kg-1. The main elements contained in the sample are Fe, Ti, Si, and Al. Meanwhile, other elements have small concentrations (<2%). Based on XRD analyses, magnetite and ilmenite are the main minerals with varying concentrations in each sample. The correlation analysis shows that magnetic susceptibility has a weak correlatio...
Heliyon, 2021
Almost all of the iron sand found in Indonesia, from Sumatra to Papua, is sandy deposit. Despite ... more Almost all of the iron sand found in Indonesia, from Sumatra to Papua, is sandy deposit. Despite its variety of minerals, iron sand is commonly mined for low economic uses such as building material. As iron sands from different localities might have different characteristics (grain-size distribution, mineralogy, magnetic properties), such characteristics might in turn be used for provenance study or for selective mining. This study aims to examine iron sand deposits from two geographically close but geologically different regions, Lampanah and Anoi Itam, and to test the grain size distributions and their relationship with magnetic susceptibility as well as Fe content. In both Lampanah and Anoi Itam, the sizes of iron sands were predominantly medium sand (MS) and fine sand (FS), but they differed in mass percentage (M%). Generally, magnetic susceptibility increases as grain size decreases. Fe content is also grain size dependent, with higher Fe content in finer sizes. The results imply that the combination of grain size distribution and magnetic mineral composition might be used not only as a provenance indicator for iron sand deposits, but also as a criterion for selective mining.
Scientific Drilling, 2012
International Continental Scientific Drilling Program (ICDP) drilled a complete succession of the... more International Continental Scientific Drilling Program (ICDP) drilled a complete succession of the lacustrine sediment sequence deposited during the last ~500,000 years in Lake Van, Eastern Anatolia (Turkey). Based on a detailed seismic site survey, two sites at a water depth of up to 360 m were drilled in summer 2010, and cores were retrieved from sub-lake-floor depths of 140 m (Northern Basin) and 220 m (Ahlat Ridge). To obtain a complete sedimentary section, the two sites were multiple-cored in order to investigate the paleoclimate history of a sensitive semi-arid region between the Black, Caspian, and Mediterranean seas. Further scientific goals of the PALEOVAN project are the reconstruction of earthquake activity, as well as the temporal, spatial, and compositional evolution of volcanism as reflected in the deposition of tephra layers. The sediments host organic matter from different sources and hence composition, which will be unravelled using biomarkers. Pathways for migration of continental and mantle-derived noble gases will be analyzed in pore waters. Preliminary 40 Ar/ 39 Ar single crystal dating of tephra layers and pollen analyses suggest that the Ahlat Ridge record encompasses more than half a million years of paleoclimate and volcanic/geodynamic history, providing the longest continental record in the entire Near East to date.
Journal of Physics: Conference Series
Proceedings of the 2014 International Conference on Physics, 2014
A geothermal system is basically a system where heat is transferred from the internal part to the... more A geothermal system is basically a system where heat is transferred from the internal part to the surface of The Earth dominantly by conduction, convection, or both. The spatial variation of the magnitude of conductive heat transfer represented by lateral variation of observed surface heat flow values is heavily related to the subsurface temperature distribution, the pattern of which is directly controlled by the variation of rock thermal conductivity values. Therefore, the information about subsurface temperature distribution may provide insight for the interpretation of the thermal structure of a region, within a more regional framework of geothermal systems in particular. In this research, we performed a numerical forward modeling procedure of 2-D conductive heat transfer using finite difference solution of the steady state heat conduction equation via a Gauss-Seidel scheme. The main physical parameters used as the input in the modeling procedure are rock thermal conductivity values as well as temperature boundary conditions. The modeling scheme was applied on two different synthetic common geothermal system geometries, one within a volcanic setting and one within a sedimentary environment, by using appropriate thermal conductivities and temperature boundary conditions for the assumed lithologies within each respective setting. The results of the modeling procedure were able to effectively characterize the thermal structure and surface heat flow patterns of the geothermal system in both environments.
Frontiers in Earth Science
Among the 19 segments of the Great Sumatran Fault (GSF), the Sianok segment is unique due to its ... more Among the 19 segments of the Great Sumatran Fault (GSF), the Sianok segment is unique due to its proximity to active volcanoes as well as to the sizable Maninjau Caldera. Located next to the Sumani to its southeast, the Sianok segment also passes through a relatively densely populated area. To identify potential disasters in the future, it is imperative to understand the subsurface structures of the Sianok segment. In this study, ground magnetic measurements were conducted, and the data were combined with the Bouguer anomaly map. Hand samples were also collected and measured for magnetic susceptibility and density. The values were later used as initial parameters for modeling. Joint forward modeling of magnetic and gravity was then used in the modeling stage as well as in the interpretation stage. Subsurface models of 20 km in depth were then formulated based on the magnetic and gravity data. The models show shallow magma chambers beneath Maninjau Caldera, Mount Marapi, and Mount Si...
IOP Conference Series: Earth and Environmental Science, 2021
Ironsand deposits might contain Fe as well as other valuable elements and minerals that could be ... more Ironsand deposits might contain Fe as well as other valuable elements and minerals that could be used in a variety of applications. Often, high Fe content deposits are preferable for exploration. An earlier study shows that the highest Fe content is found in the very fine sand (VFS) size. In this study, seven VFS samples from Anoi Itam were subjected to magnetic measurements as well as X-Ray florescence (XRF), X-Ray diffraction (XRD), and correlation analyses to investigate further characteristics and how magnetic susceptibility correlates with the elemental composition of ironsand. Magnetic susceptibility varies from 2207.77 × 10-8 m3 kg-1 to 4476.68 × 10-8 m3 kg-1. The main elements contained in the sample are Fe, Ti, Si, and Al. Meanwhile, other elements have small concentrations (<2%). Based on XRD analyses, magnetite and ilmenite are the main minerals with varying concentrations in each sample. The correlation analysis shows that magnetic susceptibility has a weak correlatio...
Heliyon, 2021
Almost all of the iron sand found in Indonesia, from Sumatra to Papua, is sandy deposit. Despite ... more Almost all of the iron sand found in Indonesia, from Sumatra to Papua, is sandy deposit. Despite its variety of minerals, iron sand is commonly mined for low economic uses such as building material. As iron sands from different localities might have different characteristics (grain-size distribution, mineralogy, magnetic properties), such characteristics might in turn be used for provenance study or for selective mining. This study aims to examine iron sand deposits from two geographically close but geologically different regions, Lampanah and Anoi Itam, and to test the grain size distributions and their relationship with magnetic susceptibility as well as Fe content. In both Lampanah and Anoi Itam, the sizes of iron sands were predominantly medium sand (MS) and fine sand (FS), but they differed in mass percentage (M%). Generally, magnetic susceptibility increases as grain size decreases. Fe content is also grain size dependent, with higher Fe content in finer sizes. The results imply that the combination of grain size distribution and magnetic mineral composition might be used not only as a provenance indicator for iron sand deposits, but also as a criterion for selective mining.
Scientific Drilling, 2012
International Continental Scientific Drilling Program (ICDP) drilled a complete succession of the... more International Continental Scientific Drilling Program (ICDP) drilled a complete succession of the lacustrine sediment sequence deposited during the last ~500,000 years in Lake Van, Eastern Anatolia (Turkey). Based on a detailed seismic site survey, two sites at a water depth of up to 360 m were drilled in summer 2010, and cores were retrieved from sub-lake-floor depths of 140 m (Northern Basin) and 220 m (Ahlat Ridge). To obtain a complete sedimentary section, the two sites were multiple-cored in order to investigate the paleoclimate history of a sensitive semi-arid region between the Black, Caspian, and Mediterranean seas. Further scientific goals of the PALEOVAN project are the reconstruction of earthquake activity, as well as the temporal, spatial, and compositional evolution of volcanism as reflected in the deposition of tephra layers. The sediments host organic matter from different sources and hence composition, which will be unravelled using biomarkers. Pathways for migration of continental and mantle-derived noble gases will be analyzed in pore waters. Preliminary 40 Ar/ 39 Ar single crystal dating of tephra layers and pollen analyses suggest that the Ahlat Ridge record encompasses more than half a million years of paleoclimate and volcanic/geodynamic history, providing the longest continental record in the entire Near East to date.
Journal of Physics: Conference Series
Proceedings of the 2014 International Conference on Physics, 2014
A geothermal system is basically a system where heat is transferred from the internal part to the... more A geothermal system is basically a system where heat is transferred from the internal part to the surface of The Earth dominantly by conduction, convection, or both. The spatial variation of the magnitude of conductive heat transfer represented by lateral variation of observed surface heat flow values is heavily related to the subsurface temperature distribution, the pattern of which is directly controlled by the variation of rock thermal conductivity values. Therefore, the information about subsurface temperature distribution may provide insight for the interpretation of the thermal structure of a region, within a more regional framework of geothermal systems in particular. In this research, we performed a numerical forward modeling procedure of 2-D conductive heat transfer using finite difference solution of the steady state heat conduction equation via a Gauss-Seidel scheme. The main physical parameters used as the input in the modeling procedure are rock thermal conductivity values as well as temperature boundary conditions. The modeling scheme was applied on two different synthetic common geothermal system geometries, one within a volcanic setting and one within a sedimentary environment, by using appropriate thermal conductivities and temperature boundary conditions for the assumed lithologies within each respective setting. The results of the modeling procedure were able to effectively characterize the thermal structure and surface heat flow patterns of the geothermal system in both environments.