Field Anomalies Research Articles

A Novel Method for Estimating Model Parameters From Geophysical Anomalies of Structural Faults Using the Manta-Ray Foraging Optimization

The Manta-Ray Foraging Optimization has been adapted and implemented in computing model parameters from potential field anomalies originating from two-dimensional dipping faults. The inversion technique was originally demonstrated on magnetic anomalies from uncorrupted–then, corrupted synthetic datasets. Thereafter, it was experimented on profiles taken from mining fields in the United States, and Australia. The results obtained showed that the design procedure is admirably stable and flexible, especially when dealing with noisy data. It is also notably efficient in the quantitative resolution of geophysical inverse problems. The consistency in results obtained from analysis of deep-seated and shallow field examples, even when compared against background results, is also impressive. The new technique has also exhibited notable superiorities over other well-known and conventional techniques, especially on the grounds of convergence rate, cost, and quality of resolved anomaly parameters. Consequently, it is recommended for interpretation of other structures and modeling of other geophysical data like self-potential and resistivity data.

Concise Historic Overview of Strain Sensors Used in the Monitoring of Civil Structures: The First One Hundred Years.

Strain is one of the most frequently monitored parameters in civil structural health monitoring (SHM) applications, and strain-based approaches were among the first to be explored and applied in SHM. There are multiple reasons why strain plays such an important role in SHM: strain is directly related to stress and deflection, which reflect structural performance, safety, and serviceability. Strain field anomalies are frequently indicators of unusual structural behaviors (e.g., damage or deterioration). Hence, the earliest concepts of strain sensing were explored in the mid-XIX century, the first effective strain sensor appeared in 1919, and the first onsite applications followed in the 1920′s. Today, one hundred years after the first developments, two generations of strain sensors, based on electrical and fiber-optic principles, firmly reached market maturity and established themselves as reliable tools applied in strain-based SHM. Along with sensor developments, the application methods evolved: the first generation of discrete sensors featured a short gauge length and provided a basis for local material monitoring; the second generation greatly extended the applicability and effectiveness of strain-based SHM by providing long gauge and one-dimensional (1D) distributed sensing, thus enabling global structural and integrity monitoring. Current research focuses on a third generation of strain sensors for two-dimensional (2D) distributed and quasi-distributed sensing, based on new advanced technologies. On the occasion of strain sensing centenary, and as an homage to all researchers, practitioners, and educators who contributed to strain-based SHM, this paper presents an overview of the first one hundred years of strain sensing technological progress, with the objective to identify relevant transformative milestones and indicate possible future research directions.

INTERPRETASI DATA GEOMAGNETIK UNTUK MENDETEKSI SEBARAN BATUAN MENGANDUNG MINERAL LOGAM DI AWANG BANGKAL, KABUPATEN BANJAR

Research has been carried out to detect the presence and distribution of rocks containing metallic minerals. Almost every object used every day contains metal elements, so the presence of metal is very important to support every human activity. The presence of metal minerals in nature is generally quite a lot, but the types of metallic minerals vary. The geomagnetic method is a geophysical method that can detect subsurface rocks containing metallic minerals based on the difference in the magnetic field between the rock and the surrounding rock. Processing of geomagnetic data obtained in the field begins with daily correction and correction of the earth's main magnetic field (IGRF). The correction results obtained are anomaly of the earth's magnetic field which is distributed horizontally on the surface. The results of the analysis in the form of local magnetic field anomalies (∆H) are divided into 3 (three) regions, the first having a value between -236.5 nT to -8 nT (nano tesla) as an area that has a high local magnetic field anomaly value. Second, the value of -377.2 nT to -236.4 nT as an area that has a moderate anomaly value. Third, the low anomaly values ranged from -778.4 nT to -377.1 nT. Areas that have high local magnetic field anomaly values are interpreted as ultramafic rocks, which are source rocks of nickel lateric deposits rich in ferromagnesian minerals, distributed in the southeastern part of the study area.

Dynamic Activity Index for Feature Engineering of Geodynamic Data for Safe Underground Isolation of High-Level Radioactive Waste

In this study, we developed a new approach for feature engineering in geosciences. The main focus of this study was feature engineering based on the implementation of the dynamic activity index (MDAI) as a function of the anomaly of the spatial distribution of data, using systems and discrete mathematical analysis. The methodology for calculating MDAI by groups, geomorphological variability, the density of tectonic faults, stress-strain state, and magnetic field anomalies, is presented herein for a specific area. A detailed analysis of the correlation matrix of MDAI revealed weak correlations between the development features. This showed that the considered properties of the geological environment are independent sets and can be used in the analysis of its geodynamic stability. As a result, it was found that most of the territory where high-level radioactive waste (HLRW) disposal is currently planned is in a relatively stable zone.

Satellite magnetic anomalies with a smooth spectral transition to long wavelengths

In most cases, the magnetic field anomalies from satellite data and models are determined by using a cut-off degree that splits the Earth's internal magnetic field (supposed to be of the core and lithospheric origin) into long-wavelength and a short-wavelength parts. This practice allows to effectively compare the signal of both components with other models and controls the signal content as well. In this study an alternative approach is followed to provide the components in long and short wavelengths without cutting the spectrum. Instead, we seek iteratively for the signal loss when the magnetic signal (from degree 1 to the maximum degree of the model) is propagated from the core-mantle boundary to satellite altitude. The problem is generally non-unique, it is required that the signal fit has to follow the slope of the geomagnetic spectrum over the lowest degrees (the degrees least affected by the magnetic lithosphere). The tool operates in the spatial domain – the spectral slope criterion is met after the procedure ends by selecting an appropriate solution. The method can be applied to the vector components individually as soon as they are given in the Earth-fixed Earth-centered frame, for which the integral equation is valid. The obtained magnetic anomalies have different spectral properties because the transition from the long wavelengths to the short wavelengths becomes smooth, although the appropriate number of iterations is questionable. It is found that the long-wavelength signal hands over the magnitude dominance to the short-wavelength part at around degrees 16 to 18.

The electromagnetic anomalies recorded by CSES during Yangbi and Madoi earthquakes occurred in late May 2021 in west China

This work analyzed the electromagnetic field (EM) anomalies recorded by the electric field detector (EFD) and the search coil magnetometer (SCM) onboard the China Seismo-Electromagnetic Satellite (CSES) during the two earthquakes (EQ), which are the Yangbi Ms6.4 EQ on May 21 (China Standard Time, CST) and the Madoi Ms7.4 EQ on May 22 (CST), 2021. These two EQs successively occurred in West China. The prevailing frequency band excluding the interferences from the satellite platform was chosen to extract convincible seismic-related EM disturbances. Two criteria were put forward to obtain reliable precursors using the Kp and Dst index and the variation rate of Dst per hour to eliminate the tinier spatial perturbations. We found that the seismic-related EM disturbances mainly appeared 1–10 days before the two earthquakes within the spatial extension of 1000 ​km above the epicenters.

СТРОЕНИЕ ВОДОНОСНЫХ ГОРИЗОНТОВ ПО АНОМАЛИЯМ МАГНИТНОГО ПОЛЯ И СИЛЫ ТЯЖЕСТИ

The results of the study of the main characteristics and structural features of the aquifer systems of cold and thermal waters on the example of well-known sources in the Middle East are presented. The study of groundwater aquifers was carried out on the basis of the technology of geophysical data complex interpretation, taking into account the features of the aquifers geological structure. Aquifers and underground reservoirs are visualized as zones of reduced magnetization and density of rocks on deep petrophysical sections calculated from magnetic field and gravity anomalies. Horizontal subterranean water conduits can be clearly traced on the areal distributions of magnetization and density along the stretches of the lineaments with reduced values. Vertical subterranean water conduits stand out vividly on magnetic and density sections in the form of ascending tracks. As a result of the study of deep sections through the zones of known thermal springs, an estimate of the dependence of the source temperature on the depth of the feeding underground reservoirs was obtained. The article examines the potential of underground resources aquifers of the arid territories of Israel, the Kingdom of Saudi Arabia and the United Arab Emirates, for which the relevance of the water problem, apparently, will not decrease in the coming decades. The forecast of the location of groundwater karst reservoirs can be carried out by magnetic and density sections, taking into account two-dimensional models of the distribution of magnetization and density of rocks. The methodology of the study of aquifer systems is applicable to the analysis of underground resources of Africa and the Middle East arid regions.

ГЕОДИНАМІКА

The purpose of the work is the analysis and geological-tectonic interpretation of the anomalous gravity field of the Ukrainian Carpathians and adjacent territories, as well as the construction of a density model of the Earth's crust and upper mantle according to the international PANCAKE seismic profile. The need to build a density model along the PANCAKE profile is due to the significant interest of a number of geologists and geophysicists in the results of seismic research along this profile. It is also caused by certain discrepancies in the seismological models of different authors. The gravity modeling technique, used in the work, includes the analysis of geological-geophysical maps and models. They are related to the geological-tectonic structure of the research region, to the creation of the initial structural part of the model and to the determination of the densities of strata and blocks of the model. The geometry and densities of the model are refined by the selection method, which is based on the interactive solution of the direct problem of gravimetric and the analysis of the reasons for the inconsistency of the calculated gravity field and Bouguer anomalies. A qualitative correspondence of the density model to the tectonic interpretation of the seismic section along the PANCAKE profile was achieved by using the methods of gravity modeling. The modelling results confirm the four-layer structure of the Earth's crust: the sedimentary cover, the upper, middle, and lower parts of the crust, which differ significantly in density. There is also evidence of the difference of the ALCAPA lithospheric plate, Flysch Carpathians and Precambrian Craton in Earth's crust and upper mantle structure. The ALCAPA plate is characterized by a small thickness (up to 29 km) and a low density of the Earth's crust. The density of the ALCAPA upper mantle is lower (3.20-3.21×103 kg/m3) compared to the upper mantle under the Ukrainian Carpathians and the East European Craton (3.28-3.30×103 kg/m3). This may be related to a change of a mantle composition and increased heat flow under ALCAPA. The Ukrainian fragment of the East European craton in the PANCAKE profile zone is characterized by a typical thickness of the crust (~41-45 km). The upper part of the crystalline crust, in contrast to the middle (2.86-2.90×103 kg/m3) and the lower part (2.98-3.10×103 kg/m3), is characterized by a lower density and greater differentiation in horizontal direction and with depth (from 2.66×103 kg/m3 to 2.86×103 kg/m3). The complex transition zone (subduction zone, Carpathian Orogen) between the ALCAPA microplate and the East European Craton causes an intense negative Bouguer anomaly – the Carpathian gravity minimum, which reaches -90×10-5 m/s2. It has a complex nature: Neogene and Paleogene-Cretaceous flysch rocks low density (≤2.50×103 kg/m3) of the Boryslav-Pokuttia cover, the main huge Precarpathian sub-vertical fault (>4 km) on the extreme southwestern slope of the platform (relatively local factors) and significant deepening of the MOHO surface under the Carpathian structure (regional factor). According to our density model, the depth of the MOHO under the front of the Carpathian thrust reaches 56 km.

СТРОЕНИЕ ТЕКТОНОСФЕРЫ И УСЛОВИЯ ФОРМИРОВАНИЯ МОЗАМБИКСКОГО ХРЕБТА: ПЛОТНОСТНОЕ И ФИЗИЧЕСКОЕ МОДЕЛИРОВАНИЕ

The tectonosphere and formation conditions of the Mozambique Ridge are considered. The Mozambique Ridge is located in the southwestern part of the Indian Ocean between the Natal and the Mozambique Mesozoic Basins. The way how the ridge formed remains debatable. The anomalous structure of the crust of the Mozambique Ridge can be explained either by underplaying - thickening of the oceanic crust from below due to magmatism, or by stretching and thinning of the continental crust. Based on gravitational and magnetic field anomalies, seismotomography and other geological and geophysical information, density modeling was carried out along four profiles. Physical modeling determined the conditions of formation of the Mozambique Ridge. It formed due to the splitting of the African-Antarctic continent, the presence of structural heterogeneities in the lithosphere of the African continent and the influence of the Karoo plume.

Detection and Analysis of Magnetic Field Anomalies over Surface Defects of Complex-Profile Parts

Detection and Analysis of Magnetic Field Anomalies over Surface Defects of Complex-Profile Parts

Identification of Gold Mineralization Zones Using Magnetic Data at Gunung Gupit Area, Magelang, Central Java

Indonesia is one of the biggest gold producing countries in the world. the discovery of new gold reserves makes the passion of the gold mining industry increase. The Gunung Gupit area of Magelang Regency in Central Java has discovered new gold potential, but has not been thoroughly explored. The magnetic method is applied to identify and determine the distribution of the presence of gold mineralized zones based on the magnetic properties of rocks. A total of 1001 points on 41 magnetic line were acquired using Proton Precession Magnetometer (PPM) Geometrics model G-856 in an area of 2.5 km2. Field data is obtained as Magnetic Field Anomaly. Reduction to pole (RTP) and low-pass filter process is applied to the magnetic anomaly. The results showed the Gunung Gupit area was divided into 4 zones based on magnetic anomaly responses, i.e strong, medium, weak anomaly and igneous rock zones. The 2.5 D modeling result shows the presence of northwest-southeast normal fault and strike slip fault that is perpendicular to the normal fault. These faults control the hydrothermal alteration in Gunung Gupit and its surroundings. A strong mineralization zone lies between these two faults. The presence of gold and other metal minerals lies in this strong mineralization zone, and moderate alteration. The coverage area is quite wide and distributed along the two faults.

Seismic Wave Field Anomaly Identification of Ultra-Deep Heterogeneous Fractured-Vuggy Reservoirs: A Case Study in Tarim Basin, China

Ultra-deep (7500–9000 m) Ordovician tight limestone heterogeneous fractured-vuggy reservoir is an important target of FuMan Oilfield in Tarim Basin. The strike-slip fault controlled reservoir is related to formation fracture and dissolution caused by geological stress. The seismic wave-field anomaly characteristics with different energy and irregular waveform are displayed in the seismic profile. Accurate identification of fractured-vuggy reservoirs wrapped in tight limestone is the direct scheme to improve production efficiency. Therefore, a new combination method flow of seismic wave-field anomaly recognition is proposed. In this process, the seismic data must be preprocessed initially, and on this basis, robust formation dip scanning is carried out. Secondly, the dip data is applied to the transverse smoothing filter to obtain the formation background data. Eventually, the seismic wave-field anomaly data is the residual between background data and original seismic data. This method has been applied in blocks with different structural characteristics and can effectively improve the resolution of strike-slip fault controlled reservoirs. Based on the results, the drilling success rate is increased to more than 95%, and the high-yield rate of oil tests is increased to 75% in 2021. Multiple applications indicate that the method is robust and can be popularized.

Structure of the Western Tibetan Vortex inconsistent with a thermally-direct circulation

The Western Tibetan Vortex (WTV) is a large-scale circulation pattern identified from year-to-year circulation variability, which was used to understand the causal mechanisms for slowdown of the glacier melting over the western Tibetan Plateau (TP). A recent argument has suggested the WTV is the set of wind field anomalies resulting from variability in near-surface air temperatures over the western TP (above 1500 m), which, in turn, is likely driven by the surface net radiation. This study thereby evaluates the above putative thermal-direct mechanism. By conducting numerical sensitivity experiments using a global atmospheric circulation model, SAMIL, we find a WTV-like structure cannot be generated from a surface thermal forcing imposed on the western TP. A thermally-direct circulation generated by the surface or near surface heating is expect to cause upward motions and a baroclinic structure above it. In contrast, downward motions and a quasi-barotropic are observed in the vertical structure of the WTV. Besides, we find variability of the surface net radiation (sum of the surface shortwave and longwave net radiation) over the western TP can be traced back to the WTV variability based on ERA5 data. The anticyclonic (cyclonic) WTV reduces (increases) the cloudiness through the anomalous downward (upward) motions, causes more (less) input shortwave net radiation and thereby more (less) surface net radiations, resulting in the warmer (cooler) surface and near-surface air temperature over the western TP. The argument is constructive in encouraging examination of the radiative balance processes that complements previous studies.

THE INVESTIGATION OF KADIDIA GEOTHERMAL FIELD (INDONESIA) USING GRAVITATIONAL DATA AND POWER SPECTRUM ANALYSIS

Kadidia is one of the area with geothermal potential in Central Sulawesi, Indonesia. Therefore, this study aims to estimate the depth of reservoir and identify subsurface geological structures using gravity data and power spectrum analysis. It uses secondary data from the field survey results of the geophysical team from the Mineral and Geothermal Resource Center Agency. Furthermore, the data were processed to obtain a complete Bouguer anomaly, reduction in a flat field, regional and residual anomalies. The results of residual anomalies showed high and low values in the range of (5-13) mGal corresponding to volcanic rocks and in the range of -10 to -4 mGal spread evenly in the study area respectively. The analysis of derivative showed the presence of intrusive rocks which are thought to be granite, and the power spectrum showed that the heat source rocks from the geothermal system were inferred as granite at a depth of more than (3.68-6.00) km. In addition, the reservoir rocks were interpreted as low-density sandstones at a depth of (0.80-1.37) km, and a caprock in the form of sandstones with medium density at a depth of (0.20-0.80) km, and from the surface to 0.20 km is soil. The interpretation of three-dimensional modeling showed that the faults control geothermal manifestations, i.e. the Koalarawa and Towingkoloe faults, which extends from northwest-southeast.

Estimating the impact process of the Jeokjung-Chogye Basin in Korea from gravity field interpretation

SUMMARY The Jeokjung-Chogye Basin (JCB) is the first impact crater discovered in the Korean peninsula. The geometric centre of the exterior crater rim is demarcated by an elevation high surrounding the JCB, exceeding 200 m. The diameter of the exterior ring is approximately 6500 m, and its centre is located about 1000 m southwest of the basin centre. Using terrestrial measured gravity field interpretations such as dip curvature and Z-derivative analysis of the residual anomaly field, we calculated the diameters of the peak ring and uplift ring to be about 4000 and 1500 m, respectively. The centre of the peak ring is located approximately 350 m to the west of the centre of the exterior ring; meanwhile, the centre of the uplift ring is located about 300 m to the east from the exterior ring's centre. Application of the Euler deconvolution method indicates that the depth discrepancy between the peak and uplift rings is approximately 200 m. This discrepancy indicates that the bedrock under the uplift ring has risen about 200 m following the meteorite impact. The offsets of the peak and the uplift ring's centres, relative to the diameter of the crater centre, allow us to conclude that the JCB was formed by steeply inclined impact (∼50–60° to the horizontal) from the eastern direction.

Frequency and temperature dependent electric polarization, relaxation, and transport properties of Mo and W doped BaTiO3

In this article, we report the structural, dielectric, electronic, and transport properties of Mo and W doped BaTiO3 ceramic. The BaTiO3 (BTO), BaTi0.85Mo0.15O3 (BTMO), and BaTi0.85W0.15O3 (BTWO) samples were prepared by double sintering ceramic technique. The X-ray diffraction patterns confirmed the tetragonal phase of the perovskite structure with the P4mm space group including some extra phases in BTMO and BTWO. A relaxation peak in the real part of electric modulus M'' is observed for BTO and BTMO at 3kHz. The dielectric constants, (εr' , εr'') and loss tangent (tanδ) for all samples were measured from 300 K to 450 K under the application of 100kHz electric field and temperature dependent dielectric anomalies ensure a ferroelectric (tetragonal) to paraelectric (cubic) phase transition in all samples. BTO and BTMO crystals display between normal ferroelectric and ideal relaxor behavior while BTWO crystal approaches to ideal relaxor ferroelectric behavior identified as canonical relaxor. Moreover, solid–liquid state anisotropy during the phase transition in all samples has been illustrated in terms of Fröhlich entropy. Apart from this, in BTO and BTWO samples, the conduction mechanism is highly dominated by the frequency of applied field compared to BTMO sample. Moreover, all studied samples exhibit semiconducting behavior with positive temperature coefficient of resistance (PTCR) effect in between 300 K and 450 K. The BTMO sample with maximum PTCR peak (2.9%/K at 415K) may find suitability for temperature controlled device application.

A Calculation Method of Magnetic Anomaly Field Distribution of Ellipsoid with Arbitrary Posture

The ellipsoidal magnetization model has a wide range of application scenarios. For example, in aviation magnetic field prospecting, mineral prospecting, seabed prospecting, and UXO (unexploded ordnance) detection. However, because the existing ellipsoid magnetization formula is relatively complicated, the detection model is usually replaced by a dipole. Such a model increases the error probability and poses a significant challenge for subsequent imaging and pattern recognition. Based on the distribution of ellipsoid gravity potential and magnetic potential, the magnetic anomaly field distribution equation generated by the ellipsoid is deduced by changing the aspect ratio, making the ellipsoid equivalent to a sphere. The result of formula derivation shows that the two magnetic anomaly fields are consistent. This paper uses COMSOL finite element software to model UXO, ellipsoids, and spheres and analyzes magnetic anomalies. The conclusion shows that the ellipsoid model can completely replace the UXO model when the error range of 1nT is satisfied. Finally, we established two sets of ellipsoids and calculated the magnetic anomalous field distributions on different planes using deduction formulas and finite element software. We compared the experimental results and found that the relative error of the two sets of data was within [Formula: see text]‰. Error analysis found that the error distribution is standardized and conforms to the normal distribution. The above mathematical analysis and finite element simulation prove that the calculation method is simple and reliable and provides a magnetic field distribution equation for subsequent UXO inversion.

On the applicability of electromagnetic monitoring of hydraulic fracturing

The purpose of this work is to assess the possibilities of using electromagnetic monitoring to study the development of a fracture system generated by hydraulic fracturing (HF) with a specified position of the controlled source. The option with the source (a vertical electric dipole) located in the interval of the oil-bearing formation and ground-based measurements was chosen as the most promising monitoring plan. We have built a geoelectric model equivalent to the system of hydraulic fractures, divided into 11 zones corresponding to HF stages. For the selected model, mathematical simulation was performed by solving the direct problem considering the impact of the steel casing, the presence of which reduced the effect. Despite this fact, no strong distortion of electromagnetic field anomaly was observed above the HF zone. Analysis of the simulation results at different HF stages showed that as new hydraulic fractures appeared and were filled with electrically conductive proppant, the total effect increased. The data on electric field anomaly demonstrated maximum deviation from the background level of more than 2 %. Provided that the studied formation is characterized by sufficient electrical conductivity, its magnetic field also becomes informative.

Basement Mapping of the Fucino Basin in Central Italy by ITRESC Modeling of Gravity Data

Sediments infilling in intermontane basins in areas with high seismic activity can strongly affect ground-shaking phenomena at the surface. Estimates of thickness and density distribution within these basin infills are crucial for ground motion amplification analysis, especially where demographic growth in human settlements has implied increasing seismic risk. We employed a 3D gravity modeling technique (ITerative RESCaling—ITRESC) to investigate the Fucino Basin (Apennines, central Italy), a half-graben basin in which intense seismic activity has recently occurred. For the first time in this region, a 3D model of the Meso-Cenozoic carbonate basement morphology was retrieved through the inversion of gravity data. Taking advantage of the ITRESC technique, (1) we were able to (1) perform an integration of geophysical and geological data constraints and (2) determine a density contrast function through a data-driven process. Thus, we avoided assuming a priori information. Finally, we provided a model that honored the gravity anomalies field by integrating many different kinds of depth constraints. Our results confirmed evidence from previous studies concerning the overall shape of the basin; however, we also highlighted several local discrepancies, such as: (a) the position of several fault lines, (b) the position of the main depocenter, and (c) the isopach map. We also pointed out the existence of a new, unknown fault, and of new features concerning known faults. All of these elements provided useful contributions to the study of the tectono-sedimentary evolution of the basin, as well as key information for assessing the local site-response effects, in terms of seismic hazards.

Mercury's Northern Rise Core-Field Magnetic Anomaly.

We use magnetic field data collected in orbit around Mercury by the MErcury Surface, Space ENvironment, GEochemistry and Ranging satellite, to detect a regional magnetic field anomaly that is spatially associated with Mercury's Northern Rise topographic signature. Regional spectral analysis indicates a source depth at or below the core‐mantle boundary, and hence the anomaly is of core, not crustal, origin. This observation supports previous studies linking the Northern Rise to a deep‐seated gravity anomaly and reveals connections among core, mantle, and crustal dynamics, likely enabled by Mercury's thin mantle.