Anomalous Body Research Articles

Review of variability of radiogenic heat properties of some rock types as a basis for geothermal characterization in Nigeria

The southwestern part of Nigeria is one of the three known regions in Nigeria with geothermal prospect. It is characterized by distinctly different thermal state and surface thermal manifestations. Although a number of geophysical explorations have been undertaken, but studies on fundamental geothermal theory remain scarce, including a lack of high-quality heat flow determinations and thermal structure studies. Heat production and heat flow properties play a very critical role in the study of thermal structure in a region. In this report, heat production and heat flow data of rock samples from published studies from some localities in Nigeria was compiled. To optimize this data, the rock-type denominations from the original studies was classified. This was used to characterize the thermal structure of the areas for possible geothermal exploration and radiogenic heat production distribution for the different rock types in the region. This gave some useful guidelines to lithospheric thermal modeling. From the heat production data, there is a wide range in values with igneous rocks having a maximum 11.17 µWm-3 and the metamorphic rocks having 131.37 µWm-3 as maximum value. The metamorphic rocks have higher values than the igneous rocks while the heat flow compiled for the country area has a minimum of 29 mWm-2 and a maximum of 130 mWm-2 with a mean value of 80 mWm-2. The high heat flow observed from data of the southwest zones may suggest the existence of anomalous heat source body in crust due to the radiogenic heat of the solid crust. This work is also an appraisal to direct attention to the lack of thermal properties investigations in the southwestern part of Nigeria and the need to improve on the heat flow database of Nigeria. Hence some parts of the study areas could be further explored for geothermal energy using appropriate geophysical techniques.

Application of electrical resistivity imaging to detection of hidden geological structures in a single roadway

Abstract Locating concealed geological structures in coal seams on both sides of a coal mine excavation roadway is of vital importance for safe production. Conventional electrical resistivity imaging methods mostly arrange observation systems on the roadway roof and floor, so they are inevitably deficient when it comes to detecting concealed geological structures in coal seams. According to the electric field distribution characteristics of artificial field sources for electrical resistivity imaging methods and utilizing the shielding of current by roadway cavities, this paper proposes the parallel coal seam detection method that arranges observation systems in coal seams on the roadway side to detect concealed geological structures in coal seams. On the basis of introducing the principles of consequent detection methods, this paper investigates the influence of roadway cavities on observation results and offers a method of correcting the influence of roadway cavities. In view of the geoelectric characteristics of typical concealed geological structures in working faces, this paper establishes numerical models to verify the feasibility of the parallel coal seam detection method. As indicated by the calculation results, the consequent pole–dipole (A-MN) observation system is the most ideal in terms of dividing the geoelectric interfaces of concealed geological structures in working faces, and its detection effect is influenced significantly by the coal seam thickness and the electric differences between surrounding rock and anomalous bodies. Coal seam resistivity slightly influences detection of the consequent pole–dipole system. According to practical application effects, the parallel coal seam detection method can solve the problem of detecting concealed geological structures in “single-roadway” working faces.

The Detached Self: Investigating the Effect of Depersonalisation on Self-Bias in the VisualRemappingof Touch.

There is a growing consensus that our most fundamental sense of self is structured by the ongoing integration of sensory and motor information related to our own body. Depersonalisation (DP) is an intriguing form of altered subjective experience in which people report feelings of unreality and detachment from their sense of self. The current study used the visual remapping of touch (VRT) paradigm to explore self-bias in visual-tactile integration in non-clinical participants reporting high and low levels of depersonalisation experiences. We found that the high-DP group showed an increased overall VRT effect but a no-self-face bias, instead showing a greater VRT effect when observing the face of another person. In addition, across all participants, self-bias was negatively predicted by the occurrence of anomalous body experiences. These results indicate disrupted integration of tactile and visual representations of the bodily self in those experiencing high levels of DP and provide greater understanding of how disruptions in multisensory perception of the self may underlie the phenomenology of depersonalisation.

A Site of Unsettlement

A Site of Unsettlement

Application of high density electricity method in detection of concealed water conveyance tunnel

We used the high density electricity method to detect underground water conveyance tunnel in a project, then we compared the difference of apparent resistivity profiles between Schlumberger device and Winner device. Lastly, we analyzed the difference between the combined inversion method and the Levenberg-Marquardt method in Res2dinv software, and inferred the trend and depth of underground water tunnel through the results of electrical detection. Several conclusions are drawn as follows. Firstly, the resistivity anomaly of underground tubular object is more prominent in Schlumberger device than in Winner device. Secondly, the Levenberg-Marquardt inversion method which contained in Res2dinv software can easily conceal the horizontal resistivity variation characteristics of small-scale tubular anomalous body and the horizontal resolution of the original apparent resistivity profile is higher than that of the inversion result. Thirdly, the combined inversion method can improve the horizontal resolution of resistivity method for detecting tubular anomalous body with larger burial depth and smaller scale.

Ground-wire Source TEM 3D Full Time Multinary Inversion Using Adaptive Regulation

Ground-wire source transient electromagnetic method (GTEM) provides better investigation ability than loop source TEM at a given noise level and decay time. However, at the present time, the method still stays in the one-dimensional inversion interpretation stage. Since actual geological structures are three-dimensionally distributed, the three-dimensional electromagnetic forward and inversion are crucial for understanding the electromagnetic responses of complex geological structures. Moreover, the traditional 3D smooth inversions of geophysical data have been found to inaccurately reflect small-scale and isolated anomalies. In this study, a multinary inversion method was introduced and applied to GTEM inversions. It was found that the proposed method had the ability to enable GTEM to more accurately delineate anomalous bodies when applied to detect high-resistivity target. Then, for the purpose of avoiding the need for multiple inversion tests to determine the regularization factors, a self-adaptive scheme was proposed based on the differences between the data fitting functional and the model functional during each iteration step. It was observed that by introducing the multinary inversion with adaptive regulation, more stable and accurate inversion results were obtained. In the current study, the numerical simulation results had successfully verified that the proposed multinary inversion method had provided better resolution than the traditional inversion methods.

Resistivity-depth Imaging with the Airborne Transient Electromagnetic Method Based on an Artificial Neural Network

We developed an artificial neural network to map the distribution of geologic conductivity in the earth subsurface using the airborne transient electromagnetic method. The artificial neural network avoids the need for complex derivations of electromagnetic field formulas and requires only input and transfer functions to obtain a quasi-resistivity image. First, training sample set from the airborne transient electromagnetic response of homogeneous half-space models with different resistivities was formed, and network model parameters, including the flight altitude, time constant, and response amplitude, were determined. Then, a double-hidden-layer back-propagation (BP) neural network was established based on the mapping relationship between quasi-resistivity and airborne transient electromagnetic response. By analyzing the mean square error curve, the training termination criterion of the BP neural network was determined. Next, the trained BP neural network was used to interpret the airborne transient electromagnetic responses of various typical layered geo-electric models, and the results were compared with that from the all-time apparent resistivity algorithm. The comparison indicated that the resistivity imaging from the BP neural network approach was much closer to the true resistivity of the model, and the response to anomalous bodies was better than that from an all-time apparent resistivity. Finally, this imaging technique was used to process field data acquired by employing the airborne transient method from the HuaYin survey area. Quasi-resistivity depth sections calculated with the BP neural network and the actual geological situation were in good.

Comparative study of 3D joint inversion based on multi-section resistivity data

A 3D joint inversion of 2D electrical prospecting data can effectively solve the shortcomings of the 2D electrical method in detecting the spatial forms of anomalous bodies. However, the direction and interval between 2D electrical prospecting survey lines can affect the workload of field prospectors and the accuracy of the subsequent 3D inversion. This study established a physical model of an indoor water tank. Multiple sections of 2D electrical survey lines were laid and survey line data was acquired. The intersection angles between 2D electrical survey lines and anomalous bodies as well as the relations between the 3D inversion characteristics and 2D electrical prospecting data for different line intervals were studied. The results of this study indicate that the electrical response of cylindrical anomalous bodies tends to become weaker, first slowly and then faster, with a decrease in the angle. When the intersection angle is between 60° and 90°, the inverted forms of the anomalous bodies are unchanged. When the interaction angle is less than 60°, there is a significant twisting of the bodies and the electrical response is obviously weaker. The 3D joint inversion imaging using multi-section resistivity data can effectively improve the recognition on the spatial forms of objects. However, the joint inversion obtained with different survey line intervals varies in how precisely the objects are depicted. The increase in the interval between survey lines can be divided into four main stages in terms of the 3D joint inversion. To maintain the efficiency of practical prospecting and because survey data forming shallow strata are affected by external interference, it was found experimentally that the optimum interval for the effective depiction of the locations and forms of objects ranges from 8 cm to 12 cm. Specifically, the least number of 2D survey lines can be deployed while ensuring the overall accuracy and reliability of the survey result when the survey line interval/2D electrical prospecting inversion depth ranges from 8/17 to 12/17. The study results may help us to guide the arrangement of electrical survey lines in field prospecting and improve construction efficiency and the accuracy of joint inversion.

Geophysical evidence for doming during the Pan-African/Brasiliano orogeny in the Seridó belt, Borborema Province, Brazil

The Neoproterozoic Seridó belt located in the Borborema Province, NE Brazil, was deformed and metamorphosed in the Pan-African/Brasiliano orogeny. The basement rocks of the belt were submitted to intense partial melting to form dome-like structures as documented in the Santa Luzia anatetic dome. The aeromagnetic map of the Seridó belt shows a long-wavelength anomaly with elongated sigmoidal shape, whose limits coincide with shear zones. Comparison with gravity data shows that both anomalies share common sources, which are felsic rocks more magnetic and less dense than the surrounding crust. Correlation with geology shows that the geophysical anomalies are associated with magnetite-rich migmatites and granites. We modelled the geophysical datasets using magnetic susceptibility and density values from measurements in cores of a stratigraphic borehole. The results are consistent with a migmatite-dome system formed in the south-central part of the belt. This large-scale crustal structure is composed of elongated internal domes, which were geophysically modelled as four anomalous bodies, that resulted from partial melting of rocks mostly of the basement. The anomalies define an elongated migmatite-dome system with the main axis in the NNE-SSW direction that progressively bends to E-W approaching to the Patos shear zone, thus indicating that this shear zone had a key role in shaping the domic structure. The migmatitic domes of the Seridó belt compose a fault-related dome system, formed in association with the broad strike-slip shear zone array of the Patos-Seridó system, which evolved through the crustal extrusion resulting from the continental collisions that amalgamated West Gondwana in the Ediacaran.

High density crustal intrusive bodies beneath Shillong plateau and Indo Burmese Range of northeast India revealed by gravity modeling and earthquake data

Modeling and analysis of gravity and earthquake data of a critically dynamic northeastern region of India assumes a special significance for understanding the seismicity and geodynamics. In this paper, the relation between lateral heterogeneity of gravity interfaces with subsurface structures, and seismic characteristics of northeast India are studied in detail to understand the seismicity and dynamics of the region using Bouguer gravity, earthquake and magnetotelluric data. The modern scaled power spectral analysis of gravity data has brought out crustal lateral heterogeneity at a depth of 8.33 km, 19.73 km and 37.14 km that correlate well with 10 km upper crust, 20 km lower crust and a Moho at 28–42 km revealed by 1D seismic crustal velocity and tomography studies. The inferred crustal depths support thinner crust over uplifted Shillong Plateau and gradual increase of depths over subduction interface of Indo Burmese Range. 2D gravity modeling constrained by seismic velocity model and 3D Euler deconvolution technique along two specific E-W and three N-S regional gravity transects delineated three significant high density anomalous heterogeneous intrusive bodies presumably due to underplating beneath Shillong Plateau, Mikir Massif and Indo Burmese Range. Based on the seismicity and stress pattern analysis through seismic ‘b’-value variation, we infer that the study region exhibits compressive stress concentrations in the form of brittle deformation at shallow depths and weakening of lower crust by high density intrusive (mafic/Ultramafic) bodies of ductile nature which may cause intense seismicity besides the ongoing collision of north drifting Indian plate with Eurasia to the north and the eastern subduction interface of Indo Burmese Range. We also infer that the NE to NW trending V-shaped areas outlined north of Shillong plateau, south of Mikir massif and NE-SW trending thrust Belt of Schuppen exhibit aseismic nature and may be the future impounding seismic sources in this region.

An interpolating scaling functions method with low-storage five-stage fourth-order explicit Runge-Kutta schemes for 3D ground penetrating radar simulation

Accurate and efficient 3D simulation is extremely important for both grasping the features of radar wave propagation in realistic models and the high-resolution inversion. In this paper, we propose a new numerical algorithm called the low-storage five-stage fourth-order explicit Runge-Kutta interpolation scaling function method (LSERK-ISFM) and apply it into the 3D simulation of ground penetrating radar (GPR). Firstly, we derive the auxiliary differential equation (ADE) of the 3D Maxwell's equations based on the complex-frequency shifted perfectly matched layer (CFS-PML), discretize the spatial derivative of the Maxwell equation by ISFM, and integrate the temporal dimension through the LSERK scheme. Compared with the traditional finite-difference time-domain (FDTD) method, the LSERK-ISFM algorithm can effectively improve the precision of space-time dispersion of the Maxwell's equations. Specifically, by the homogeneous vacuum medium model, we compare the forward modeling results of the different number of grids per wavelength, the comparison results prove that a smaller number of grids per wavelength can be selected in the LSERK-ISFM scheme, which can greatly contribute to reducing the consumption of memory. Then we build a simple 3D model to properly compare the proposed algorithm with the coarse-mesh FDTD and the fine-mesh FDTD, the results show that, with the same mesh generation, the LSERK-ISFM algorithm outperforms the conventional FDTD algorithms in terms of both accuracy and efficiency. Finally, we test the algorithm on a 3D complex model by a series of 3D forward profiles and the corresponding slices, both simulated reflections and diffractions clearly depict the shape and location of the anomalous bodies, which shows great potential of application in the field of 3D exploration and interpretation for GPR community.

INVESTIGATION OF SUBSURFACE STRUCTURES WITHIN PARTS OF NIGER DELTA, NIGERIA, VIA AEROMAGNETIC DATA

Geophysical study involving aeromagnetic method was carried out to investigate parts of Niger Delta in Nigeria, aimed at investigating the cause and nature of anomalous bodies within the study area. Spectral analysis technique was employed in quantitative interpretation to determine depth/thickness of the sedimentary basin, basement topography, structural trends, curie point depth, thermal gradient and heat flow in the area. The total magnetic intensity (TMI) anomalies had values of between -53.7nT and 119.5nT while the residual magnetic intensity ranged from -52.5 to 58.0nT. The spectral analysis revealed the depth to magnetic sources varying from 2.5 to 5.5km while the shallow magnetic sources varied from 0.89 to 1.47km. The geothermal analysis revealed the curie point depth between 11.782 and 18.048km while the calculated geothermal gradient ranged lie between 32.137 and 49.231o𝐶𝑘𝑚−1. The heat flow values ranged from 80.343 to 123.080𝑚𝑊𝑚−2. The results from this study have thrown more light to the understanding of the variation of subsurface structures in the study area. These will enhance the development of the resources and will be of economic benefit to the country if well harnessed. However, possible future research work on this active area is proposed for more robust results.

Body representations and basic symptoms in schizophrenia

Patients with schizophrenia report a wide range of anomalous body experiences. According to the basic symptom model of schizophrenia, disturbances of body perception and awareness are among the most powerful predictors of the changes in the subjective experience of the self in schizophrenia. In this study we first investigated the body structural representation (BSR), a specific aspect of body awareness, and its association to basic symptoms in patients with schizophrenia. Using a finger localization task, we found that patients are significantly less accurate than healthy controls when asked to identify pairs of fingers touched by the experimenter, when the hand is hidden from view. Most importantly, patients' performance at the finger localization task was negatively associated to basic symptoms: the worse the individual accuracy, the higher the SPI-A total score. Moreover, the accuracy at the finger localization task was also negatively correlated with the malleability of the sense of body ownership: the less the individual ability to localize fingers, the stronger the rubber hand illusion. These results are in agreement with the idea that self-disorders in schizophrenia reveal a disconnectedness that can be regarded as a problem of disembodiment and traced back to abnormal body experiences.

Anomaly shape inversion via model reduction and PSO

Most of the geophysical inverse problems in geophysical exploration consist in detecting, locating and outlining the shape of geophysical anomalous bodies imbedded into a quasi-homogeneous background by analyzing their effect in the geophysical signature. The inversion algorithm that is currently used creates a very fine mesh in the model space to approximate the shapes and the values of the anomalous bodies and the geophysical structure of the geological background. This approach results in discrete inverse problems with a huge uncertainty space, and the common way of stabilizing the inversion consists in introducing a reference model (through prior information) to define the set of correctness of geophysical models. We present a different way of dealing with the high underdetermined character of this kind of problems, consisting in solving the inverse problem using a low dimensional parameterization that provides an approximate solution of the anomaly via Particle Swarm Optimization (PSO). This methodology has been designed for anomaly detection in geological set-ups that correspond with this kind of problem. We show its application to synthetic and real cases in gravimetric inversion performing at the same time uncertainty analysis of the solution. We have compared two different parameterizations for the geophysical anomalies (polygons and ellipses), showing that we have obtained similar results. This methodology outperforms the common least squares method with regularization.

Instantaneous resistivity vector difference used to simulate the seepage of polymer flooding in an oilfield

The instantaneous resistivity vector difference provides a method for monitoring the predominant seepage path of oil in real time remaining in a reservoir by numerical simulation. The target stratum in Shahejie Formation, Bohai Bay Basin, eastern North China has a relatively high resistivity (15–25 Ω m), which is reduced to 3–10 Ω m with the in-pouring of viscous polymer–water solutions. The instantaneous resistivity (ρt) of each monitored well-point changes with the continuous injection of polymer. Mitchell's improved model calculates ρt for every well-point at time t, and its reliability is verified by the core-displacement and production-logging methods. Using first-order differences and a differential model to recognize anomalous changes in the target zone, we can effectively extract and highlight changes in the resistivity of the target layer caused by polymer injection, and determine the distribution of resistivity. The position of maximum change in instantaneous resistivity in each direction can be calculated using second-order differences, with the zero line reflecting the boundary position of the anomalous body. The ρt differential results is consistent with 3H tracking results. This study aimed to determine the characteristics of the predominant seepage field in the study area, provide real-time technical support for the deployment and adjustment of polymer flooding schemes avoiding an inefficient polymer cycle, and improve the tertiary recovery factor of oilfields.

A Weighting Function-Based Method for Resistivity Inversion in Subsurface Investigations

There is a high demand for high detection accuracy and resolution with respect to anomalous bodies due to the increased development of underground spaces. This study focused on the weighted inversion of observed data from individual array type electrical resistivity tomography (ERT), and developed an improved method of applying a data weighing function to the geoelectrical inversion procedure. In this method, the weighting factor as an observed data weighting term was introduced into the objective function. For individual arrays, the sensitivity decreases with increasing electrode interval. Therefore, the Jacobian matrices were computed for the observed data of individual arrays to determine the value of the weighting factor, and the weighting factor was calculated automatically during inversion. In this work, 2D combined inversion of ERT data from four-electrode Alfa-type arrays is examined. The effectiveness of the weighted inversion method was demonstrated using various synthetic and real data examples. The results indicated that the inversion method based on observed data weighted function could improve the contribution of observed data with depth information to the objective function. It has been proven that the combined weighted inversion method could be a feasible tool for improving the accuracies of positioning and resolution while imaging deep anomalous bodies in the subsurface.

Noninvasive geophysical integrated survey at Madonna del Giglio (Sabine necropolis, Magliano Sabina, Latium, Central Italy)

Nondestructive geophysical methods are increasingly used for the investigation of archaeological sites, where a detailed physical and geometrical reconstruction of structures is required in order to explore and document the presence of subsurface structures related to cultural heritage. The aim of this work was to detect buried features in an unexplored area of the Sabine necropolis (VII–IV century B.C.) called Madonna del Giglio (Latium, Central Italy). For the surveys, ground-penetrating radar (GPR) and fluxgate gradiometry methods have been employed. We applied time slice techniques for GPR data and 2D normalized cross-correlation on magnetic data in order to obtain a planimetric view at different depths of anomalous bodies. The results obtained with GPR were confirmed by those taken employing fluxgate gradiometry. Furthermore, it should be stressed that the anomalies detected by the GPR are positioned almost on the limit of the plateau of Madonna del Giglio and downhill, toward the residential area of Magliano Sabina, where, in 1992, archaeological excavations revealed the presence of the necropolis, highlighting an extremely unclear stratigraphic situation. The integrated noninvasive geophysical proposed in this study was extremely useful for tracing the complex archaeological framework in order to pursuit cultural heritage preservation and valorization.

Numerical modelling analysis of multi-source semi-airborne TEM systems using a TFEM

Abstract Traditional transient electromagnetic methods use single sources for excitation and extract the characteristics of underground media by improving interpretation technology. This study focused the improvements of transient electromagnetic interpretation using complex source technology. A time-domain vector finite element method (TFEM) was applied on three-dimensional forward modelling of semi-airborne transient electromagnetic (TEM) with multiple electrical sources, and it analysed the characteristics of fields with multiple sources. The study used a model of an isolated anomalous body in a homogeneous medium as an example. The effects of different combinations of excitation sources on the distributions of the magnetic field characteristics were analysed. Numerical results showed that the magnetic field components in a specific area could be strengthened by changing the layout of the sources, which was significant for future field data collections. By comparing the transient electromagnetic fields of the vertical array dipole sources with that of the loop source, the anomaly transient electromagnetic field of multi-source was more obvious than the field with a single source. Taking a complex orebody model as an example, a cross-electric source was used to calculate the magnetic field components of the semi-airborne TEM method. The resistivity distribution characteristics of the underground medium were obtained using an apparent resistivity interpretation method of the vertical magnetic field, which fully demonstrated that a multi-source transient electromagnetic system had the ability to determine abundant resistivity information of a complex medium.

Research and Application of In‐seam Seismic Survey Technology for Disaster‐causing Potential Geology Anomalous Body in Coal Seam

AbstractIn order to effectively detect potential geology anomalous bodies in coal bearing formation, such as coal seam thickness variation, small faults, goafs and collapse columns, and provide scientific guidance for safe and efficient mining, the SUMMIT‐II EX explosion‐proof seismic slot wave instrument, produced by German DMT Company, was used to detect the underground channel wave with the help of transmission method, reflection method and transflective method. Region area detection experiment in mining face had been carried out thanks to the advantage of channel wave, such as its great dispersion, abundant geology information, strong anti‐interference ability and long‐distance detecting. The experimental results showed that: (1) Coal seam thickness variation in extremely unstable coal seam has been quantitatively interpreted with an accuracy of more than 80% generally; (2) The faults, goafs and collapse columns could be detected and predicted accurately; (3) Experimental detection of gas enrichment areas, stress concentration regions and water inrush risk zone has been collated; (4) A research system of disaster‐causing geology anomalous body detection by in‐seam seismic survey has been built, valuable and innovative achievements have been got. Series of innovation obtained for the first time in this study indicated that it was more effective to detect disaster‐causing potential geology anomalies by in‐seam seismic survey than by ground seismic survey. It had significant scientific value and application prospect under complex coal seam conditions.

Anomalous localization at the boundary of an interacting topological insulator

The boundary of a topological insulator (TI) hosts an anomaly restricting its possible phases: e.g. 3D strong and weak TIs maintain surface conductivity at any disorder if symmetry is preserved on-average, at least when electron interactions on the surface are weak. However the interplay of strong interactions and disorder with the boundary anomaly has not yet been theoretically addressed. Here we study this combination for the edge of a 2D TI and the surface of a 3D weak TI, showing how it can lead to an "Anomalous Many Body Localized" (AMBL) phase that preserves the anomaly. We discuss how the anomalous Kramers parity switching with pi flux arises in the bosonized theory of the localized helical state. The anomaly can be probed in localized boundaries by electrostatically sensing nonlinear hopping transport with e/2 shot noise. Our AMBL construction in 3D weak TIs fails for 3D strong TIs, suggesting that their anomaly restrictions are distinguished by strong interactions.