Complete Bouguer Anomaly Research Articles

Global geopotential models evaluation based on terrestrial gravity data over Ethiopia

Abstract The availability of high-degree and recent global geopotential models is a crucial resource for different geodetic and geophysical applications such as modelling of geoid and quasi-geoid and establishing global reference and height systems, estimating Moho depth, gravity anomaly and tectonics, other geopotential functional, and oceanography, which emphasizes the importance for model evaluation. We have therefore estimated complete Bouguer anomalies and Moho whose results are evaluated with the terrestrial values. We validate the recently released satellite-only and high-degree combined GGMs over Ethiopia using terrestrial gravity data based on a statistical comparison of the Bouguer anomaly, its residual and Moho depth. The terrestrial-derived gravity anomaly is more accurately estimated by EIGEN6C4. The assessment against a recently conducted high resolution (∼3 km) terrestrial and airborne gravimetric survey over Ethiopia shows that EIGEN6C4/SGG_UGM_1 and 2 have the highest accuracy (∼3.28/3.27 mGal). However, the comparison with such data hardly discriminates the qualities of other GGMs that have or are truncated to the same degree and order. Whereas, the validation results of GGMs against terrestrial and airborne data are identical. EIGEN6C4, SGG_UGM_2, XGM2016, XGM2019e_2159/SGG_UGM_1 have the best quality, and the accuracy of associated Moho is 4.89/4.90 km, and this value changes to 4.98/4.91/5.51 km when the EGM08/ITSG_Grace2018s/GOCO06S are assessed.

GEOLOGICAL INTERPRETATION OF 2D GRAVITY MODELING IN TULUNG SELAPAN AREA AND SURROUNDINGS, SOUTH SUMATRA BASIN

The South Sumatra Basin is a prolific oil and gas basin. The Tulung Selapan area, which is to the east and part of the South Sumatra Basin, is considered to have hydrocarbon potential. Several sub-basins, including the South Palembang and the North Palembang sub-basins, exist in the region. One of the geophysical methods for determining the presence of sedimentary sub-basins, structural patterns, and bedrock is the gravity method. The purpose of this study is to determine the structural pattern and interpret the subsurface geological model of the Tulung Selapan area using 2D modeling. The complete Bouguer anomaly (CBA) reveals circular and relatively northwest-southeast trending patterns, ranging from +33 mGal to +62 mGal. 2D gravity forward modeling results in eight successive rock layers. From top to bottom, the uppermost layer is swamp sediment with a mass density of 2.1 g/cm3, followed successively by the sedimentary rocks of the Kasai Formation (2.28 g/cm3), the Muara Enim Formation (2.32 g/cm3), the Air Benakat Formation (2.39 g/cm3), the Gumai Formation (2.3 g/cm3), the Baturaja Formation (2.48 g/cm3), and lastly a layer with a density of 2.7 g/cm3, which represents the bedrock. Due to the limited depth of 2800 m in 2D forward modeling, it is unable to identify the source and reservoir rocks. The seal rock (caprock) is interpreted to be shale from the Gumai Formation at an average depth of 1.53 km. Based on Second Vertical Derivative (SVD) analysis, 2D modeling identifies the presence of geological structures with normal faults.

Physical modeling of magma chamber of slamet volcano by means of satellite gravimetric data

Slamet Volcano (3,432 m) is the highest volcano in Central Java, Indonesia, with a weak explosive type of eruption compared to other active volcanoes. Designing the magma chamber model may help reveal the characteristics of Slamet Volcano. The modelling uses the gravimetric satellite data from GGMplus, which is best in spatial resolution compared to other satellite data, i.e. 220 m. Data processing begins with Bouguer correction and terrain correction and has resulted in complete Bouguer anomalies data, with values ranging from 11.068 – 117.451 mGal. Further, residual Bouguer anomalies data were obtained after data reduction to the horizontal surface and removal of regional anomalies data, to obtain values ranging from -67.569 – 38.808 mGal. The residual anomaly contour map shows the lowest anomalous value is under the volcanic cone at positions of 109.21967° E and 7.24281° S which is estimated to be the location of the magma chamber of Slamet Volcano. However, the inversion modeling resulting from the residual Bouguer anomalies data shows that the magma chamber of Slamet Volcano can be observed clearly at positions of 109.22053° E and 7.24719° S. The location of the magma chamber is not perfectly vertical under the volcanic cone but has a slight slope. The obtained model of the magma chamber has a relatively small volume and shallow depth, i.e. about 1 – 4 km. The obtained physical parameters of the magma chamber impact the characteristics of the eruption of Slamet Volcano which tend to be weak explosive.

Analysis of Subsurface Structure of Sembalun Geothermal Prospect Area, East Lombok with 2D and 3D Gravity Modeling

Abstract. The existence of Indonesian geothermal is estimated to be spread in 331 locations, one of which is Sembalun, East Lombok Regency. Therefore, this study was conducted to analyze the subsurface structure of geothermal prospect areas in the area using gravity methods. Gravity data used is satellite data as much as 4275 measurement points that have been corrected free air (FAA). The data processing stage resulted in a Complete Bouguer Anomaly (CBA) map with low anomaly values to be the target of research ranging from 58.9 – 115.7 mGal located in the east (Sembalun-Bumbung) and northeast (Sembalun-Lawang). The prospect of geothermal is controlled by the Talaga fault and Pusuk fault on the caldera floor (Sembalun-Lawang). In addition, the Tanakiabang fault and the Orok fault are near the manifestation of Sebau Hot Springs and on the Caldera floor (Sembalun-Bumbung). The results of 2D modeling correlated with 3D modeling conducted inversions showed geothermal sources are estimated to have a density of 2.68 gr/cc – 3 gr/cc consisting of hornblende andesite lava rocks with a depth of >2500, reservoir layer in the form of sand that has a density of 1.4 gr/cc - 1.72 gr/cc with a depth of 700 - 1200 m and a layer of a hood in the form of alluvium rocks that have a density of 1.8 gr/cc - 2.2 gr/cc with a depth of 0 - 500 m.

ANALISIS STRUKTUR BAWAH PERMUKAAN GUNUNG IJEN BANYUWANGI

Analysis of the subsurface structure of Mount Ijen, Banyuwangi was carried out based on anomaly data obtained from satellite image data. This research was conducted with the aim of identifying the subsurface structures around the research site. In this study, what is determined is the complete Bouguer anomaly (ABL), regional and residual anomalies based on the ABL, and their inversion modeling. The results of the representation of underground structures based on residual anomalies obtained from complete and regional Bouguer anomaly data. The complete bouguer anomaly values obtained in the Mount Ijen area range from 12.2 to 110.7 mGal. In the process of separating regional and residual anomalies, different anomaly values are produced. The regional anomaly value ranges from +12.2 to +110.7 mGal while the residual anomaly ranges from -4.2 to +2.4 mGal

Investigation of the Geoid Model Accuracy Improvement in Turkey

This study investigated the accuracy improvement of the gravimetric geoid model in Turkey using densified grids of the gravity anomalies with the least-squares modification of the Stokes integral with additive corrections (LSMSA) method. In LSMSA computations of the geoid models, the surface gravity anomalies, which were derived from the complete Bouguer anomaly grid data set by forward modeling the topographic masses, were used. In the computations, in addition to the original 5′-resolution (∼9 km) Bouguer anomaly data set, its densified versions to 1′-resolution (∼2 km) also were used. The densification of the gravity grids was carried out using both planar- and spherical-type complete Bouguer anomalies. Thus, the effects of both gravity grid densification and the applied approximation for the Bouguer reduction process in gravity gridding on the geoid model accuracies were examined in order. The Bouguer gravity reductions were carried out using classical formulas for the planar approximation, whereas the gravimetric terrain corrections from the high-resolution SRTM2gravity global model were employed for the spherical approximation in numerical tests. The calculated geoid models were validated at 100 homogeneously distributed GPS/leveling (GPS means Global Positioning System) benchmarks over the country. In the tests, the geoid undulations derived from the models also were compared with the observations at six tide gauge stations along the coastlines. The latter provided an additional check for the assessment of the models’ compatibility at the coastal boundaries. In conclusion, the accuracy of the best geoid model solution (8.6 cm by means of the standard deviation of geoid undulation differences at GPS/leveling benchmarks) was achieved using 1′-resolution gravity anomalies restored from the spherical complete Bouguer anomalies in Turkey.

Gravity Studies at Cerro Machín Volcano, Colombia

A gravimetric study was performed at the Cerro Machin volcano (4° 29’ N, 75° 22’ W), Tolima Department, Colombia, to obtain a density distribution of the volcanic edifice and its basement. This study was divided into three main sections. The first section consisted of gravimetric measurements on the volcano, which were performed with a Scintrex Autograv CG-5 gravimeter. In the second section, a complete Bouguer anomaly was obtained by applying gravimetric corrections to the field data, such as instrumental drift, latitude, free-air, Bouguer, and topographic corrections. For the third section, we used the GM-SYS extension of Oasis Montaj to obtain a forward model of the subsurface density distribution that allowed us to explain the source of the gravimetric anomaly. As the main results for this study, we determined that the field-obtained Bouguer anomaly ranged between -87 mGal and -29 mGal in the study area. The Oasis Montaj density model allowed us to infer an elongated dacitic complex at the top of the distribution with a mean density of 2300 kg/m3, with the presence of a volcanic conduit of 2400 kg/m3 at the base. The seismicity in the area suggests that the gravimetric anomaly caused by the dome and its surrounding materials may be related to a large weakened zone at the interface between the volcanic edifice and the metamorphic basement, provoked by fault activity, interaction with the hydrothermal system and the ascent of hot, fluid material to the surface. This study suggests one interpretation of the Machin dome volcanic complex and encourages further gravimetric studies and modeling over a wider area.

The Use of Multi-Geophysical Methods to Determine the Geothermal Potential: A Case Study from the Humenné Unit (The Eastern Slovak Basin)

The exploration of the geothermal potential of a geological unit has multiple aspects. The most important elements are the geological structure, the hydrogeological conditions, and heat flow. The analysis of the above-mentioned elements attempts to help maximize the use of a geothermal aquifer’s potential. When choosing the most appropriate geophysical method, it is important to consider various factors, such as basic structural parameters as well as the total cost of exploration. This is especially true for low-thermal areas. Comparison of multi-geophysical exploration methods used in the study of the carbonate aquifer of the Humenné Unit identified the advantages and weaknesses of each method. The Humenné Unit is the north basement unit of the Eastern Slovak Basin (with a heat flow value ranging from 100 to 125 mW·m−2), which is part of the Pannonian Basin (with a high heat flow ranging from 50 to 130 mW·m−2). The calculation of the geothermal potential was based on the results of several methods. Some important geophysical survey methods resulted in: (a) deep seismic cross-sections which clarified the position and overall internal structure of the aquifer (b) gravimetric measurements in the form of a map of the Complete Bouguer Anomalies (calculated for density 2.67 g·cm−3) which confirmed the presence of structural elevations and depressions. These elevations and depressions intensified the water yield, heat flow and raised the overall temperature (c) the use of geoelectric resistivity profiling, which is a fast and cheap method, but is limited by depth. The similar resistivities ρ: 80–360 Ωm of carbonates and andesites was a serious problem. The specific heat-energy potential has a wide range of 0.337–19.533 GJ/m2. The highest values above 15 GJ/m2 are reached in areas where the temperature on the surface of the Triassic carbonates exceeds 90 °C.

Analisis Data Gravitasi Untuk Identifikasi Struktur Bawah Permukaan Daerah Potensi Panas Bumi Cipari

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.

Preliminary Study of Probolinggo Active Fault in East Java Based on Gravity Method

The Gravity Method based on TOPEX satellite data is a one of geophysical method which from satellite observations. The gravity method investigate the gravitational field from one to another observation point. The principle of this method has the ability to distinguish the mass material density from its environment, so that the subsurface structure can be identified. In this research, gravity method is used to identify subsurface structures that are suspected of Probolinggo Fault and identify the rock lithology. From TOPEX we get free air anomaly and then applied the correction process to obtain Complete Bouguer Anomaly (CBA) value. The CBA value is processed interpolation to create CBA map, and then the map is filtered by butterworth to obtain regional and residual maps. The value of high gravity acceleration is 0.076 - 19.74 mGal indicating compact rocks. Meanwhile, based on the residual anomaly map, the value of smaller gravity acceleration is -0.92 - 0.9 mGal indicates lower compacting rocks with smaller mass. The gravity acceleration contrast on the residual anomaly, on the north side of fault line (0.12 mGal to 0.45 mGal) and on the south side (-0.92 mGal to -0.043 mGal), is interpreted as normal fault. Furthermore, 3D modelling shows density value less than 2 gr/cm3 we can interpret as pyroclastic fall, in between 2 gr/cm3 until 2.4 gr/cm3 is sandstone and more than 2.4 gr/cm3 is igneous rock such as andesit. 2D slicing modelling show presence the shear fault, so we can suspect this area have oblique fault with west-east direction.

Identification of Subsurface Rock Structure of Non-Volcanic Geothermal Systems Based on Gravity Anomalies (Terak Village, Central Bangka Regency)

Abstract
 
 Geothermal manifestations on Bangka Island are found in the villages of Terak, Pemali, Sungailiat/Pelawan, Dendang, Permis, and Nyelanding. The manifestation of hot water in Terak Village, Central Bangka Regency is in the form of 3 hot springs with a surface temperature of 55ᵒC this research is to be carried focus on the structure of the subsurface rock layers using the geophysical method, namely the gravity method. The data used are topography and Free Air Anomaly. The data processing is in the form of Bouguer Correction and Terrain Correction to obtain the Complete Bouguer Anomaly (CBA) value. Then the CBA value is separated from regional anomalies and residual anomalies using the upward continuation method, as well as 2D modeling interpretation (forward modeling). From the research results, it is known that the subsurface rock structure of the non-volcanic geothermal system in Terak Village in the form of sandstone (2.28 – 2.49 gr/cm3) at a depth of 0 – 1.44 km is estimated as caprock, granite (2.77 – 2.78 gr/cm3) at a depth of 0 – 1.8 km is estimated as reservoir rock, and diorite rock (2.87 – 2.99 gr/ cm3) at a depth of 0 – 2 km is estimated as basement rock.
 

Utilization of Gravity Satellite Data to Imaging Subsurface Conditions, Case Study: Lake Toba, North Sumatera

The purpose of this study is to utilize satellite gravity data for free to interpret subsurface conditions. The data can be obtained from the topex site with a latitude range is +/-80,738. The author tries to interpret the gravity data for Lake Toba, North Sumatra. The area is attractive because it has a sizeable geological object in the form of a large lake and a fault called the Sumatran fault. This gravity data is processed like ordinary gravity processing so that Complete Bouguer Anomaly (CBA) is obtained, then regional-residual separation is carried out using a moving average. From CBA, it can be seen that there are two closures just below Lake Toba. There are two possible chambers under Lake Toba, namely the central and southern parts. In addition, it is also clear that the lineament of the Sumatran fault is also visible, as well as three other lineaments which may be faults that are not identified from the surface. So, we can take advantage of this free gravity satellite data for interpretation of sizeable geological objects that can be applied to other areas. It is helpful to know the general picture of regional geology before conducting a more detailed survey.

Identification 2D Modelling of Subsurface Structure Geothermal Prospect Area by Gravity Method: Case Study in Tanuhi, South Kalimantan

Geothermal potential in Kalimantan is rare because the island does not have an active volcano. In addition, when viewed from the subsurface structure, Kalimantan Island is in medium-low enthalpy with hot sprung as one of the geothermal potentials, which are generally in the immature water zone. One of the areas is Tanuhi Hot Springs, South Kalimantan. Therefore, this study was conducted to determine the geothermal system of the area using the gravity method. The gravity data processing stage produces the CBA value (Complete Bouguer Anomaly) which is then separated using the Butterworth filter method. Judging from the CBA map, the results of the qualitative interpretation show that the geothermal potential is in a low anomaly with a value of (-19.4 mgal) – (-14. 2 mgal) which is marked in the dark blue. While the results of the quantitative interpretation resulted in the cross-sectional modeling of SW-NE (Southwest – Northeast) and NW-SE (Northwest - Southeast) with a total of 3 layers. The layer consists of granite, clay, and sand mixed with granite. Both models are dominated by sand mixed with granite with the density value at cross-section SW-NE and cross-section NW-SE is the same, namely 2770 kg/m3.

Bouguer Anomaly of Geothermal Reservoir at Tiris Area, Probolinggo, East Java, Indonesia

Research related to the geothermal system in the Tiris geothermal area (TGA) Probolinggo Regency has been conducted using the gravity method. This study aims to investigate the subsurface structure, with a target on estimating geothermal reservoir rocks from the study area. This study utilized the Gravity meter La Coste & Romberg type G-1503 on 116 acquisition points in an area of 2.16 km2, covering all geothermal manifestation points in TGA. The gravity measurement data obtained is then processed through gravity corrections, which include: conversion into milli-Gals (mGal) units, tidal correction, drift correction, latitude correction, free air correction, Bouguer correction, and terrain correction. These corrections to obtain a complete Bouguer anomaly (CBA) value. The study area shows the CBA value on a horizontal plane which ranges from 0.1 mGal to 4.2 mGal. The separation of the regional and residual Bouguer anomaly from the CBA on a horizontal plane employed the Moving Average method through spectrum analysis. The value of residual Bouguer anomaly ranges from -0.7 mGal to 2.7 mGal. The low anomalies are scattered in the northwest, and a small number are spread in the northeast and southeast, while the high anomalies are in the middle of the study area. The result of 3D inversion modeling finds that the study area's subsurface structure consists of four rock layers, namely lapilli tuff, tuffaceous breccia, volcanic breccia, and basalt. Volcanic breccia is approximated as geothermal reservoir rocks at a depth of 700 to 1000 meters below the acquisition point. In contrast, basalt is supposed to be intrusive igneous rock because it tends to break through the surface at a depth of 348 to 350 meters below the acquisition point. The presence of these intrusive rocks can be predicted through spectrum analysis result, which shows a regional anomaly source at a depth of 348 meters below the acquisition point. This intrusion rock is suspected to be a heat source rock in the geothermal system in the study area.

Thermal zone identification by gravity data modeling using Euler deconvolution and geochemical analysis of hot springs in Saurashtra and Cambay Basins

Objective: This study is aimed at interpreting geochemical and geophysical data of 4 locations in Gujarat, India to understand the subsurface geothermal hotspot locations. Methods: CG-5 gravimeter was used to collect the gravity data. Data corrections were done to obtain a complete Bouguer anomaly. The depth of the dense bodies was calculated using Euler deconvolution. Also, the geochemical classification of physiochemical properties of geothermal spring waters of the locations was evaluated to assess their possible applications. Findings: In the sample region, the complete Bouguer anomaly analysis ranges between 1.99 mGal-2.23 mGal. The Euler deconvolution produced depth solutions ranging from 100 to 450 meters, which were mostly found near gravity highs, and the presence of deep structures can be deduced. These deep structures are translated as dense intruding bodies trapped by an overlying cap rock. The Geochemical analysis was done of the four samples. Based on the results of various plots such as Ternary, Durov, Piper, Stiff, the waters are graded as cationic with Na+K and anionic with Cl+SO4. The sample waters indicate suitability for drinking and irrigation at some locations. Finding these hotspots and exploiting them is of importance for these areas which are dealing with the acute water crisis. Novelty: Euler deconvolution of gravity data was first time applied for subtle geothermal trap identification in Saurashtra and Cambay basins. It has been established through this study that surface manifestation of these subtle traps are the hot springs. Systematic geochemical characterization of the hot springs progressed the nascent geothermal energy research of India. Keywords: Bouguer anomaly; Heat source; Geothermal energy; Geochemical analysis; Hot spring; water analysis

2D Forward Modeling Geothermal System Gravity Data in South Solok Region, West Sumatra

Indonesia has the greatest potential for geothermal energy in the world. Geothermal has an important role as an alternative fuel because it is a renewable energy source, but its use has not been maximized. One of the areas that have the greatest potential for geothermal energy in South Solok, West Sumatra. Therefore, this study was conducted to determine the geothermal system in the South Solok area, West Sumatra by using the gravity method. The gravity data processing stage requires some software to get the CBA value(Complete Bouguer Anomaly), map contours of the CBA. Anomaly separation with the butterworth filter method, determination of residual anomaly slice points, and 2D modeling of geothermal systems. Based on modeling, the qualitative interpretation interprets the Complete Bouguer Anomaly map which is suspected as a geothermal prospect area is a low anomaly ranging from 7.9 mgal - 9.4 mgal which is marked in dark blue. Meanwhile, quantitative interpretation produces modeling of the AB and CD slicing with a total of four layers. This layer consists of clay rock as a cap rock, sandstone as a reservoir, granite as a heated rock as a heat source, and the last layer in the form of magma as a heat source. The anomaly modeling of these two sections is dominated by granite rock with a density value of 2500 kg/m3 for the AB section and 2550 kg/m3 for the CD section.

Structural interpretation of the south-western flank of the Anambra Basin (Nigeria) using satellite-derived WGM 2012 gravity data

The Anambra Basin in the west of the lower Benue Trough is one of Nigeria's most petroliferous provinces. The subsurface structure has been extensively studied using various geophysical methods except for the mapping of structural lineaments. For the present study, the satellite-derived World Gravity Map 2012 (WGM 2012) global gravity model was utilized to study structural features located at different depths. Upward continuation at the height of 30 km was used to extract the regional anomaly from the Bouguer anomaly. The residual anomaly was determined after the deduction of the regional gravity anomaly from the Bouguer anomaly. The total horizontal derivative (THD) of the complete Bouguer, regional, and residual anomalies was used to map the lineaments. The Bouguer gravity anomaly ranges from −58 to more than +28 mGal and presents two generic trends in the E-W and NNE-SSW directions. The regional Bouguer anomaly reveals a Moho depth of 38.0 km from the CRUST1.0 model. The amplitude pattern of the residual gravity anomaly was used to distinguish seven high residual anomalies (HR1-HR7) and four low residual anomalies (HL1-HL4). The residual anomalies of HR1-HR7 are inferred to be hypabyssal igneous rocks. The low residual anomalies of HL1-HL4 are interpreted to be Paleogene and Cretaceous deposits of the Niger Delta complex, and the Bende-Ameki, Imo, Nsukka, Ajali, Mamu, and Nkporo formations. Based on THD analysis, the major structural trends are found to be in NE-SW and NW-SE directions. In addition, 2.5-dimensional forward modelling using the residual Bouguer anomaly along profile CD was performed, providing a variation of the basement depth between 3.5 km and 6.5 km. Therefore, the sedimentary thickness is adequate for the recommended minimum depth for source rock formation and petroleum accumulation with respect to the other petroleum system elements.

Application of Moving Average (MA) and Upward Continuation Methods to Bouguer Gravity Anomaly Data for Fault Analysis of the Earthquake Risk Area of Timor and Flores Islands

An interpretation of the subsurface structure of the island of Timor and Flores has been carried out based on an analysis of gravity data. The island of Timor and Flores, which is passed by the Ring of Fire, is one of the areas that have a high seismic level. This is due to subduction zones and fault activity. Therefore, this study aims to qualitatively and semi-quantitatively analyze the existence of faults and their types by utilizing secondary data from free-air gravity anomalies. This data is processed into Complete Bouguer Anomaly (CBA) data by determining the average density of the surface using the Nettleton method. The separation of regional and residual anomalies using the upward continuation method to a height of 700 meters and the moving average method. The results of this residual anomaly are then used as input for fault analysis using the correlation profile of the First Horizontal Derivative (FHD) and Second Vertical Derivative (SVD) methods using the Elkins filter. For modelling using the Forward Modelling method on Grav2DC. Based on calculations using the Nettleton method, the average density of the surface is 1.23 gr/cm3. A fault is indicated when the FHD curve is at its minimum or maximum peak and the SVD curve is at the zero lines or close to zero. In this study, 12 slices were suspected to be the position of the fault. The average FHD value at the maximum peak is 0.989 mGal/m, while the minimum peak is 0.00038 mGal/m. The type of fault of each slice is determined from the maximum and minimum SVD value. From the research results, normal faults are in the Ruteng area (from the northwest in Nggalak to the east on Mount Wuas), Ende (from the Wulangmang mountains to the northwest to the southeast), and Kupang, while the ascending fault is in the Ruteng area (from the west sea on Mount Wuas straight to the southeast towards Ruteng), Ende (from Bajawa to the east towards Nangapanda), and Atambua. The results of this interpretation are also strengthened by overlaying the suspected fault with the geological map of the study are a and showing the suitability of the fault position even though the fault location is not the same.

Identification of The Geothermal Heat at Mount Iyang-Argopuro Based on a Data Image of Landsat 8 Satellite and a Data Gravity of GGMPlus Satellite

In Indonesia is the Iyang-Argopuro Volcano Complex. The Research uses remote sensing methods and gravity methods conducted to study thermal anomalies and subsurface structures using Data images of Landsat 8 satellite and a data gravity of GGMPlus satellite. Moreover, the study aims to estimate the number of hoisting manifestations of the earth's heat at the compound of the Iyang-Argopuro volcano. Landsat 8 satellite image data is a spectral band (band 1-9) and a thermal band (band 10 and 11). The data was done in radiometric corrections, radiance correction, and reflex corrections, and was thus obtained a value of ground surface temperature (LST). The data was done in radiometric corrections, radiance correction, and reflectance corrections, to get an LST value. Processing data gravity of GGMPlus satellites with a bouguer correction, terrain corrections up to get a Complete Bouguer Anomaly (ABL) value. Furthermore, the ABL value consisting of regional and local anomalies is separated using an upward continuation filter to obtain local anomaly values. The results obtained from this study are five points of geothermal manifestation locations in the Iyang-Argopuro Volcano Complex which are located in the northern, central, southern and eastern parts. Manifestations in the northern, central, and northeastern parts have ground surface temperatures of 24-31 ̊C. While manifestations in the central and eastern parts have a surface temperature of land 21-31 ̊C. The high ground temperature values at the five locations were associated with low gravity values ranging from -20 mGal to -10 mGal. The low gravity value is assumed to have a rock structure with a low-density value. Low-density rock structures have the possibility of an outflow zone causing the soil surface temperature to be relatively high.

Gravity anomaly models with geophysical interpretation of the Republic of Croatia, including Adriatic and Dinarides regions

SUMMARY Models of gravity corrections and anomalies are created and distributed over the territory of the Republic of Croatia, including the Adriatic and Dinarides regions. Published models cover the study area between 42.0°N < φ < 46.6°N and 13.0°E < λ < 19.5°E with a 1′ × 1′ resolution. Distributed models include gravity corrections and anomalies of normal gravity, atmosphere, free air, Bouguer, terrain, complete Bouguer and topographic–isostatic according to the Airy–Heiskanen model. A high-resolution digital elevation/bathymetry model was prepared from SRTMv3.0 and GEBCO2019 models. It was then used for the computation of topographic and topographic–isostatic gravity effects using rectangular prisms with constant crustal density. Gridding of the scattered gravity data was performed with the Kriging interpolation method using complete Bouguer anomalies by implementing the remove–grid–restore methodology. Developed models were interpreted providing insights into the topography-reduced (anomalous) Earth’s gravity field reflecting the variations in mass/density distribution within the crust and upper mantle over the study area.