Jambura Geoscience Review

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ISSN / EISSN : 2623-0682 / 2656-0380
Total articles ≅ 38
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Raynier Geraldino Dadu Kerong, , Fransisca Dwi Agustina
Jambura Geoscience Review, Volume 4, pp 69-85; https://doi.org/10.34312/jgeosrev.v4i1.12046

Abstract:
Advances in UAV technology produce various superior products that can be utilized for the development and analysis of natural dynamics. One of them is DTM which is a visual representation of the shape of the ground surface that is displayed in 3 dimensions. DTM is obtained from the results of DSM filtering, where all features above the ground are digitally removed using a certain method. To produce a good DTM, a good quality DSM is needed, therefore a Horizontal and Vertical accuracy analysis was carried out based on ASPRS 2015. In this study, two software with different data processing methods were used, namely automatic filtering and semi-automatic filtering from DSM to DTM. To determine the quality of DTM, spot-height data is used as a comparison which is considered to be the actual form in the field. From the series of data processing processes, DTM results were obtained which were then tested for accuracy utilizing statistical validation tests using the calculation of RMSEZ values and non-statistical validation tests (Visual) using the transverse profile method. The test results show that the DTM produced by the PCI Geomatica software with the semi-automatic filtering method has more accurate and precise quality than the DTM from the SAGA GIS software with the automatic filtering method with an elevation value of 1,249 m and RMSEz 3,542 m to the spot-height. Then the visualization of the DTM transverse profile produced by the PCI Geomatica software semi-automatic filtering method to the spot height also does not appear to experience a significant difference where the elevation at Point 1 is 0.5 m and Point 2 is 0.5 m.
Ninik Agustin, Agung Wibawa
Jambura Geoscience Review, Volume 4, pp 22-32; https://doi.org/10.34312/jgeosrev.v4i1.12114

Abstract:
Geothermal prospect in Cipari has been shown by spring who has a temperature of about 50°C and is categorized as a low temperature. The presence of spring on Cipari earth's surface is an indication of geothermal structures' existence on the surface and a geothermal system below the surface. Geophysical methods can be used for subsurface structures identification, one of them is the density method with gravity data. This study has an objective to identify the subsurface structures in Cipari geothermal potential area using GGMPlus gravity data. Terrain and Bouguer corrections were used to obtain Complete Bouguer Anomaly (CBA). Separation of regional and residual anomalies using Butterwoth and Bandpass filters. The rock contact boundary was obtained by the FHD method and geological structures such as faults were obtained by the SVD method. FHD and SVD results were used as information for 2D forward modeling. The ABL map shows anomalous contrasts in areas that have rock contacts and geological faults. The high anomaly in the center of the study area indicates the Cipari anticline. Data processing and analysis concluded that the area around the Cipari hot spring has anticline, several rock contacts, and normal fault structures. The fault in the study area is part of the geothermal system which is confirmed by GGMPlus data.
M Taufik Rahmadi, Eni Yuniastuti, Maulana Abdul Hakim, Ayu Suciani
Jambura Geoscience Review, Volume 4, pp 1-10; https://doi.org/10.34312/jgeosrev.v4i1.11380

Abstract:
Mangroves are one of the most productive ecosystems for human life, marine ecosystems, and coastal areas. Mangrove distribution is a distribution based on specific geographical or administrative boundaries. Kota Langsa is one of the areas that has a good representation of the distribution of mangroves. Therefore, researchers studied the Kota Langsa area because Kota Langsa is one of the areas with the largest and most diverse mangrove ecosystem in Aceh Province. This study examines the mapping of mangrove distribution using Sentinel-2A multispectral imagery with composite images of Red, Green, and Blue. This research uses SNAP software. The research stages consist of radiometric correction, atmospheric correction, and multispectral image classification. The method used in image classification is the maximum likelihood algorithm. The use of the maximum likelihood algorithm is because the maximum likelihood algorithm gives the best results among other algorithms. The development of the research is the distribution of mangroves in Langsa City, covering an area of 4727.35 ha, which is divided into three sub-districts and eleven gampong (kelurahan). The sub-districts that have mangrove distribution are East Langsa District covering an area of 3240.25 Ha (68.55%), Langsa Barat District covering an area of 1486.47 Ha (31.45%), and Langsa Lama District covering an area of 0.63 Ha (0.013).
Rizky Hizrah Wumu, Ahmad Zainuri, Noviar Akase
Jambura Geoscience Review, Volume 4, pp 60-68; https://doi.org/10.34312/jgeosrev.v4i1.12752

Abstract:
Kota Tengah Subdistrict has the highest population density in Gorontalo City, with a population density of 6,755 people/km2. This high population density requires a large amount of water to meet the needs of the population, where one form of fulfillment is taken from groundwater. For this reason, it is necessary and important to know the characteristics of aquifers. This study aims to determine the characteristics of groundwater aquifers in the Kota Tengah Subdistrict. The method used is the resistivity geoelectric method to obtain aquifer characteristics in the form of material type (lithology), depth, and thickness of the aquifer. Based on the geoelectrical analysis in TS 01 there are 4 layers, namely topsoil, clay sand, sand, and clay; TS 02 contains topsoil, sand, and clay layers; TS 03 contains topsoil, sand, and clay. The study found that the lithology of the near-surface layer in the Kota Tengah subdistrict can be classified into aquifers and aquicludes. The aquifer layer is formed by sand-sized sedimentary deposits that have high permeability while the aquiclude is clay-sized which is impermeable. The aquifer layer was found starting from a depth of 0.57 m. The average thickness of the aquifer layer was 13.8 m which is interpreted as an unconfined aquifer. This study also found other deeper aquifer layers as confined aquifers that can not be further interpreted due to the limitations of the method used.
Larasaty Ayu Parsamardhani, , Fransisca Dwi Agustina
Jambura Geoscience Review, Volume 4, pp 33-47; https://doi.org/10.34312/jgeosrev.v4i1.12013

Abstract:
Monitoring the deformation of objects in the natural disaster area is one of the anticipative steps to reduce losses. In this case, this is an attempt to implement mitigation for the safety and viability of the community. Until this time, many constraint factors in the process of obtaining information regarding the strength of the structure and the changes of shape and dimension (per time unit) of the objects, one of which is the high operational cost and the duration of data processing while using a conventional measuring instrument. Through this article, a fast, cheap, easy, and accurate alternative method to detect deformation of the bridge material structure due to flash flood is only by using a Digital Single Lens Reflex (DSLR) camera. The bridge’s structures were photographed and processed with proprietary software to obtain the retro-reflective coordinate of the target that has been evenly attached to the bridge surface as a reference point. From a series of periodic photoshoots conducted from July 2020 to July 2021, deformation of the bridge structure was successfully detected with a magnitude between 0.026 mm – 5.867 mm with a measurement accuracy level was 0.081 mm. With this measurement accuracy level, this system is able to detect the deformation of structures smaller than 0.1 mm, and even invisible deformation can still be detected. This article will explain the technique and methodology of deformation measurement quickly and accurately only with a DSLR camera.
Nani Mardiani, Sri Maryati, Ronal Hutagalung,
Jambura Geoscience Review, Volume 4, pp 48-59; https://doi.org/10.34312/jgeosrev.v4i1.8455

Abstract:
North Sulawesi has one large dam located in Pindol Village, Lolak District. The research objective was to determine the lithology of the bedrock of dam foundation, rock class, and subsurface permeability of the dam. The method used in this research is core logging analysis and water pressure test. The bedrock foundations of the dam consist of andesite units, shale units, sandstone units which are included in the Sedimentary Facies Tinombo Formation and Volcanic Tinombo Formation. The formations are included in the Eocene to Early Oligocene Eocene and deposited in the deep marine environment. The foundation rock class is predominantly CM class (rather soft and fairly weathered rock), the rock quality of design is poor-medium characterized by the presence of broken cores and easily crushed in some parts. Lolak Dam has 6 permeability zones, namely very high, high, medium, moderate, low, and very low permeability with an average lugeon value of 4.43 liters/minute. The standard of lugeon value for the dam foundation is Lu3, so it is necessary to repair the drill points on the pilot hole which has a lugeon value of 3 (low, moderate, medium, high, and very high permeability zones) to increase the capacity foundation rock.
Rakhmat Jaya Lahay,
Jambura Geoscience Review, Volume 4, pp 11-21; https://doi.org/10.34312/jgeosrev.v4i1.12086

Abstract:
Monitoring changes in vegetation cover is important for the restoration of ecosystems in the Gorontalo Regency area. The utilization of remote sensing technology makes it possible to detect the dynamics of changes in vegetation cover spatially and temporally. The Terra MODIS satellite image collection in the study area is available in large numbers and sizes. Therefore, cloud computing-based spatial technology support is needed. Google Earth Engine (GEE) as a geospatial computing device is an alternative to cover this shortfall. The aim of this study is to explore the condition of vegetation cover spatially and temporally using the GEE platform. A total of 43 MODIS images in the study area, recording periods 2000 and 2020, were used to quickly and effectively generate vegetation cover maps. The process of downloading, processing, and analyzing data was automated through the GEE interface. The results of the mapping in 2000 and 2020 are shown by maps of vegetation cover in two classes, namely; vegetation and non-vegetation. The accuracy of the vegetation cover map shows good results, namely an overall accuracy of 0.81 for 2000 and 0.85 for 2020. The area of the non-vegetation class increased by 2815.29 ha, and the vegetation class decreased by 2767.31 ha. The map of spatial changes in vegetation cover in the study area is classified into three classes, namely revegetation, devegetation, and unchanged. Based on these results, the extraction of vegetation cover changes in the study area using the GEE platform can be carried out well.
La Ode Juni Akbar, Fitryane Lihawa, Marike Mahmud
Jambura Geoscience Review, Volume 3, pp 73-83; https://doi.org/10.34312/jgeosrev.v3i2.10623

Abstract:
The purpose of this study was to determine the type of landslides and analyze the landslide slip in North Gorontalo District, Gorontalo Province using the geoelectric method. This research begins by determining the type and kind of landslides found in the North Gorontalo District. The location of the measurement was carried out at 4 (four) locations, 1st Track in Tomilito District; 2nd track in Sumalata District; 3rd track in Monano District; and 4th track in East Sumalata District. The research method used was a field survey with a land unit approach. Data analysis to determine the type and kind of landslides is using the landslide classification index method. Analysis of geoelectric measurement results using the Schlumberger-Configuration. The results showed that the types of landslides that occurred in North Gorontalo Regency were the type of planar slide, rotational slide, slide flow, rock/topples. The average depth of the landslide slip that occurred was 5 – 15.9 meters. In general, landslides that occur in North Gorontalo Regency are caused by high rainfall and land conversion for agriculture.
Ferryati Masitoh, Alfi Nur Rusydi, Ilham Diki Pratama
Jambura Geoscience Review, Volume 3, pp 84-96; https://doi.org/10.34312/jgeosrev.v3i2.10252

Abstract:
This study aims to identify the potential groundwater in Jedong, Malang, East Java. The hydrogeomorphological approach is a suitable approach to describe the relationship between hydrological and geomorphological processes on and below the earth's surface. The survey of geoelectricity complements the hydrogeomorphological approach. It will give a better description of the groundwater conditions below the earth's surface. Based on the research, there are 2 hydrogeomorphological units in the study area, which are: Volcanic Foot Valley Unit and Volcanic Foot Ridge Unit. The best groundwater potential is in Volcanic Foot Valley Hydrogeomorphological unit, namely Awar-awar Valley and Cokro Valley. The valleys are dominated by gully erosion and landslides. They have surface deposits up to a depth of 7 meters, and lots of outcrops of breccia, pumice, and andesite boulders. The valley’s springs discharge between 56 - 198 m3/day. The average infiltration rate in the valley is 1776 mm / hour, with sandy soil material. The best aquifer consisting of sandy material is more than 10 meters in depth, based on the geoelectrical survey. Water in the aquiclude layer, cannot be exploited because it is breccia and tuff material. The Sawah valley cannot be exploited further because the groundwater potential is very low. This can be identified by the thick water outflow seepage. In the Volcanic Foot Ridge Hydrogeomorphological unit, the groundwater potential is also very small. Hydrogeomorphically, water will flow down the slope to the valley. It will reduce the infiltration rate. In general, the ridge area is only used for settlement, while the slopes are used for dryland agriculture. The geoelectric analysis results show that the groundwater potential is at a depth of more than 45 meters. This research’s results show that the combination of the hydrogeomorphological approach and the geoelectric use will provide a better description of the potential groundwater.
Muhammad Riza Saputra, Deasy Arisanty, Sidharta Adyatma
Jambura Geoscience Review, Volume 3, pp 57-64; https://doi.org/10.34312/jgeosrev.v3i2.5648

Abstract:
One of the areas in South Kalimantan that is prone to land fires is the Banjarbaru area, especially on peatlands. The fire in Banjarbaru is important because of the vital object of Syamsudin Noor Airport. Mapping of fire vulnerability was important for the Banjarbaru area, which had repeated fires throughout the year. The objective of the study was to analyze the vulnerability of forest and land fires in Banjarbaru, South Kalimantan Province. This study used Landsat 8 Oli Tirs imagery to obtain NDVI data and land cover maps from INA-Geoportal. The analysis of data used the scoring and overlay of the two maps. The level of vulnerability was dominated by the high vulnerability. The high level of vulnerability in Cempaka District was 81.9 %, in Banjarbaru Selatan District was around 99.5 %, in Banjarbaru Utara District was around 95.3 %, in Landasan Ulin District was around 94.1 % and in Lianganggang District was around 88.9 %. Land cover in the form of agriculture, plantations, and shrubs with moderate-high density caused the land to be more prone to fires.
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