Journal of Geoscience, Engineering, Environment, and Technology

Numerical Simulation of Pyroclastic Flow of Karangetang Volcano Based on 2015 Eruption Activity

2023-09-29T01:10:02+07:00

On May 7-9, 2015 the eruptive activity of Mount Karangetang released pyroclastic flows towards the Batuawang River for 3.6 km and hit Kora kora village which is located south of the Main Crater. This pyroclastic flow originated from lava flows during the effusive eruption period. MODIS satellite image hotspot data shows the lava flow extrusion rate and total volume at the peak began to increase since April 2015 and continued to show an increase until December 2015, with the estimated volume and lava extrusion rate on April 22, 2015 reaching 4.16x106 m³ and 0.53 m³/s, respectively, and on December 9, 2015 the volume reached 1.67x107 m³ with a lava extrusion rate of 1.97 m³/s. The results of field checks show that this pyroclastic flow is dominated by block and ash, and by using numerical simulations show the deflection of pyroclastic flow in accordance with the flow field of the Batuawang river, and the splash of pyroclastic flow towards Kora kora village in addition to the location adjacent to the river flow and also controlled by the narrowing of the river channel due to the accumulation of material in the flow field. A total of 8 numerical simulation cases have been carried out, and in our opinion with an input volume of 500 x10³ m³ and a flow material friction of 0.5 is a case that corresponds to a flow event that reaches a distance of 3.6 km from the Main Crater. Taking into account the current activity conditions we used the same parameters to estimate the area that could be affected by pyroclastic flows in the future. Numerical simulation show that the pyroclastic flow traveled 5 km in a south-southwest direction from the top of the main crater.

Mapping the Depth of Groundwater Level and Soil Permeability Based on Geographic Information Systems (GIS) for The Feasibility of Absorption Well Locations in The Application of Ecodrain in Tuah Madani District

2023-11-03T19:41:26+07:00

The problem of flooding in Tuah Madani District, Pekanbaru City, needs attention. Drainage and flood control systems need to be made to accommodate excess water and hold water somewhere. Groundwater management is directed at creating a balance between groundwater utilization and soil conservation efforts through the application of ecodrain which affects the conditions and characteristics of the area which provides an overview of land hydrology in parcels by comparing the height of the land with the receiving water bodies. as a drainage outlet. This research aims to create a map of groundwater depth and soil permeability based on Geographic Information Systems (GIS) for the feasibility of infiltration well locations in Tuah Madani District in implementing ecodrain. The research method was carried out by collecting data on the coordinates of infiltration wells at 30 points in five areas of Tuah Madani District. then measure the depth of the groundwater table and test the permeability in the field. Data is processed using ArcGIS. The results of mapping the depth of the groundwater table in the area are classified as shallow (1.28m–3.58m). Only 4 locations (Tuah Karya and West Sidomulyo) out of 30 sample locations did not meet the standards. Meanwhile, the permability value obtained was 2.61–11.07 cm/hour. Technically, the procedure for planning infiltration wells (SNI03-2453-2002) fulfills two conditions, namely a minimum groundwater depth of 1.50 m and soil permeability ≥ 2.0 cm/hour. Based on the contour lines of Tuah Madani District, it displays a pattern of groundwater flow from high flow to low flow at each point of the wellbore, the highest points on the map are colored blue (Air Putih and Sidomulyo Barat), while the lowest points on the map are Air Putih and Sidomulyo Barat. red (Tuah Madani, Luah Karya and Sialangmunggu).

Sensitivity Analysis Based on Physical Properties to Permeability Coefficient of Cohesive Soil Using Artificial Neural Network

2023-07-20T05:42:52+07:00

Permeability is the ability of a soil to allow liquids to pass through. Of course the soil has a physical characteristic that can be known by laboratory testing. This study aims to determine the physical properties that most affect the coefficient of cohesive soil permeability using the Artificial Neural Network (ANN) tool, the results obtained will later be matched with actual conditions according to the context of engineering geology. The research method begins with an influence or sensitivity analysis using ANN which will produce a correlation coefficient (R). Then, these results will be compared with the influence analysis based on the value of the coefficient of determination (R²). After that, accuracy and error tests will be carried out using the Mean Absolute Percentage Error (MAPE), the highest accuracy values is categorized as the most influential physical property of the 7 physical property parameters, namely liquid limit, plastic limit, plasticity index, %sand, %fines, %silt, and %clay. Based on the result of the analysis, %fines is the parameter that most influences permeability and is able to make very strong predictions with an R value using an ANN of 0.9941875, an R² value of 0.6336, an accuracy of 99.6962%, and a MAPE of 0.3038%. These results are compared with the existing empirical equations with an accuracy of 96.4393% and MAPE of 3.5607%. It can be concluded that ANN is more effective and optimal in making predictions. In this case, in the context of engineering geology, the more %fines, the smaller the permeability coefficient of the soil.

Identifying Dominant Structural Pattern of Semarang City Using Digital Elevation Model and Landsat 8-OLI Imagery

2023-10-10T15:19:20+07:00

Semarang City is an area in the northern part of Java Island, administratively the Capital of Central Java Province. Because Semarang City is the provincial capital, Semarang City has a relatively dense population. Geologically, the city of Semarang is an area that consists of various types of lithology and is traversed by various regional geological structures. In this case, understanding the existence and distribution of geological structures in the city of Semarang is essential, considering that geological structures are one of the controllers for natural disasters such as landslides and earthquakes. This study analyzed the existence and distribution of geological structures in the city of Semarang based on the lineaments observed from digital elevation models and satellite imagery. This study aims to identify the dominant structural pattern in Semarang City, determine the relationship between fault fracture density (FFD) with regional geological structure and lithology, and determine the fault zone area in Semarang City based on FFD & lineament analysis. The method used in this analysis is to process DEM data and Landsat 8-OLI imagery, then interpret the lineaments in the form of rosset diagrams and the density in the form of FFD maps. The results of the rosset diagram analysis show that Semarang City has various structural lineament patterns, namely: North–South, Northeast–Southwest, and Northwest–Southeast, with the North–South pattern as the dominant pattern. Based on the results of the lineament density distribution on the FFD map, it is known that the area traversed by the Semarang regional geological structure has a high lineament density value which is interpreted that the area is a weak zone with high structural intensity. From this study, it can also be seen that there is no significant relationship between the type of lithology and the density value on the FFD map. The distribution of lineament density is not affected by the type of lithology, except in the northern and northeastern parts of Semarang city, which consist of alluvium. Based on these results, it can be interpreted that the fault zone area is associated with areas that have high-density values on the FFD map. Distribution of the fault zone area of Semarang City is spreading over the Banyumanik, Gunungpati, and Mijen Districts, which are relatively in the southern and central parts of Semarang City.

The Utilization of LiCSBAS for Deformation Monitoring in Geresa Segment of Matano Fault, Central Sulawesi, Indonesia

2023-11-02T04:26:22+07:00

Sulawesi is situated between the confluence of three plates, resulting in a very complex tectonic setting on the island. This has an impact on the occurrence of geological structures, including faults. One of them is the Matano Fault which consists of 6 segments (Kuleana Segment, Pewusai Segment, Matano Segment, Pamsoa Segment, Ballawai Segment, and Geresa Segment). The research area is located in Morowali Regency, covering the Geresa Segment. Morowali Regency recorded an earthquake with a magnitude of 5.7 in 2012. This indicates that deformation has occurred. Therefore, this study aims to identify the deformation velocity around the Geresa Segment area. The methods used are geological observation and satellite image data processing to obtain information on deformation rates. The geological field study includes aspects of geomorphology, geological structure, and the rock types distribution. Meanwhile, the processing of satellite image data in the form of InSAR is carried out through the LiCSBAS package tools that has been integrated with LiCSAR. The analysis results illustrate the difference in deformation velocity around the Geresa Segment area. The area which is composed of Tolaka formation and Ultramafic complex tends to uplift with a deformation rate of up to 17 mm/year. In addition, alluvium that covers the southeastarn part has a land subsidence of up to 7 mm/year.

Petrochemistry of Ultramafic Rock in Baula - Pomalaa Ophiolite Complex, Southeast Sulawesi, Indonesia

2023-10-31T03:51:24+07:00

Baula and Pomalaa Ophiolitic Complexes are part of East Sulawesi Ophiolite (ESO). The ultramafic rocks in the Baula and Pomalaa Ophiolite Complex mainly is peridotite and consist of harzburgite, lherzolite and olivine websterite, mostly serpentinized. Chemical and petrological research has focused on minerals, such as olivine, pyroxene, and spinel. This study examines the tectonic setting and temperature of ultramafic rock formation. Twelve ultramafic rock samples were examined using geothermometers made of pyroxene, petrographic examination, and coexisting olivine and spinel analyses. SEM and petrographic analysis of pyroxene lamellae and mylonite-ultramylonite structures allowed for the measurement of the geothermometer of ultramafic rocks. Using SEM-EDS, the coexistence of olivine and spinel was analyzed to determine the type of ultramafic tectonic setting. In the coexistence of olivine and spinel, olivine and spinel oxide compounds as tectonic setting markers in the form of Fo and Cr# values. Ultramafic rocks have different temperature levels, based on pyroxene thermometer, and the first one starts at a high temperature of 1000-1200ºC. It is characterized by thin, elongated augite lamellae. Instead, large lamellae characterize augite at medium temperatures (800–1000ºC). Irregular, anhedral, and broader forms of enstatite lamellae are typical of low temperatures (500–800ºC). Different generations of exsolution lamellae indicate that magma cooling was gradual. The distribution of #Fo ranged from 0.87 to 0.92, and Cr# values ranged from 0.13-0.19. According to coexisting olivine and spinel analysis. On the Olivine-Spinel Mantle Array (OSMA), the Fo and Cr# plot indicates that the peridotites tectonic setting was from the ocean floor and the magmatism was from MORB (Mid Oceanic Ridge Basalt). The Al₂O₃ vs. TiO₂ pattern in spinel lherzolite also similar with Ampana and Kabaena peridotites magmatism.

The Investigation of the Dominant Direction of the Fault Structure Using the Radon Method at Mt. Pancar Geothermal Field

2023-10-17T05:44:21+07:00

The Mt. Pancar geothermal field in Bogor, Indonesia, has been surveyed for radon in soil gas. There were 33 measurement points across the survey area that were separated by 100-200 meters. Through the radon method, this study aims to show the direction of the dominant fault structure based on the distribution of radon values in around observation area. The Radon concentration was measured by RAD 7 Electronic Radon Detector Durridge Company. The study showed the dominant structure was directed southwest-northeast, passing through the manifestation of the red crater. The result of radon soil gas survey performed highest radon concentration near the manifestations which was included survey area was about 10047 Bq⁄m^3. The manifestation was predicted to be controlled by the three faults in the Mt. Pancar geothermal field.

Geochemistry of Igneous Rocks of Citirem Formation and Its Implications for the Tectonic Setting in Ciletuh – Palabuhanratu UNESCO Global Geopark Area

2023-11-08T07:04:40+07:00

The igneous rocks of the Citirem Formation in the Ciletuh – Palabuhanratu UNESCO Global Geopark area petrographically not only consist of basalt, but also andesite, dacite, and gabbro. The characteristics of basalts Citirem Formation are composed of plagioclase 43% – 58% and olivine, mostly have amygdaloidal and aphanitic textures. Andesites are composed of 45% – 65% plagioclase, absence of olivine, mostly aphanitic and trachytic, some have intergranular textures. Dacite comprises 50% plagioclase, 20% quartz, and the absence of olivine, and aphanitic, intersertal textures. Gabbros are composed of 62% plagioclase, 6% – 12% olivine, with phaneritic texture. Based on the plot of the major elements vs SiO₂ diagram, MgO, FeOt (Fe₂O₃+FeO), CaO, and TiO₂ show a negative correlation with SiO₂. In comparison, Na₂O and K₂O show a positive correlation with SiO₂. The lithology of igneous rocks of Citirem Formation are basalt, trachybasalt, basaltic trachyandesite, trachyandesite, andesite, dacite and gabbro based on a plot of the Na₂O+K₂O vs SiO₂ diagram for volcanic and plutonic rocks. The origin of magma type can be distinguished based on the plot of K₂O vs SiO₂ diagrams, the igneous rocks of Citirem Formation are divided into low-K, medium-K, high-K, and shoshonite magma series. Dacite STA 2, andesite STA 7, basaltic andesite STA 8, trachyandesite STA 10 and gabbro STA 14 are calc-alkaline based on triangular diagram Th-Hf-Ta-Zr-Nb. Gabbro STA 17 indicates IAT (island arc tholeiite), trachybasalt STA 19, basalt STA 20 and basaltic trachyandesite STA 27 are E-MORB, WPT (within plate tholeiitic), In contrast, trachybasalt STA 28 is WPA (within plate alkali). Primitive mantle long, NMORB-normalized REE patterns and chondrites-normalized show some rocks have distinctive patterns that have similarities with suprasubduction zone ophiolite rocks, MORB of Mirdita ophiolite, and some show similarities with patterns from OIB and E-MORB.

Identification of Deep Groundwater Aquifer Zones with Geoelectrical Method in Sukadanaham Area Bandar Lampung, Indonesia

2023-11-10T08:48:16+07:00

Research on groundwater aquifers using the geoelectric method has been carried out in the Sukadanaham area, Tanjung Karang Barat District, Bandar Lampung City. This Research Objectives This research aims to identify the lithology and depth of groundwater aquifer zones based on resistivity values and geological literature. Data acquisition was carried out using the Schlumberger configuration of 3 points in the young Betung volcanic formation (Qhvb). The data used is the resistivity value. Resistivity value data is modeled vertically with inverted results. The resistivity value of each point is adjusted and interpolated based on the literature on rock resistivity values. Based on the identification results, 4 types of subsurface rock lithology were found, namely top soil, tuff, breccia, and andesite. The lithology of the layers at point 1, point 2 and point 3 is dominated by tuff and breccia layers. The resistivity value of the andesite layer obtained has a high value, which is > 300 Ωm. The resistivity value of the tuff layer for the waterproof layer has a value of 200-250 Ωm. The breccia layer acts as a groundwater aquifer zone with a low resistivity value of 15-60 Ωm. The rock resistivity value with the lowest value is at a depth of 40-95 m which is a compressed aquifer layer with andesite and tuff layers as a waterproof layer above and below.

The Pervious Concrete and Pervious Mortar as Water Filter in Decentralized Water Treatment– a Review

2023-10-31T00:52:16+07:00

Decentralized water treatment system is water treatment carried out by the community on a household-scale. One of the technologies that have been developed to gain freshwater is the pervious concrete filter (PCF). This study aims to provide the researchers with an understanding of the pervious concrete filter as a potential filter technology in water treatment. The method used is a literature review from several papers and reports related to pervious concrete from past to present. PCF is a filter made from a mixture of aggregate, cement, and water with a specific ratio. PCF has enough water and air permeability due to interconnected macro pores. Some properties such as porosity, permeability, and pores size determine the ability of PCF to remove the contaminants in the water. These properties were controlled mostly by the aggregate size, aggregate-cement ratio, water-cement ratio, etc. According to its characteristic, the PCF shows a prospect to be used as water filter mainly in a decentralized water treatment system. Besides, the understanding of PCF is a basis to develop a pervious mortar filter that slightly different in the aggregate sizes used in this composite.

Front matter JGEET Vol 09 No 01 2024

2024-03-22T11:23:49+07:00

Back matter JGEET Vol 09 No 01 2024

2024-03-22T11:40:54+07:00