Potential field transformation on the basis of a continuous wavelet transform

Geophysical data processing further constrained inversion is evolving progressively prevalent in geoscience domains for three-dimensional modelling and resources evaluation. The process is based on the magnetic and gravity data processing further constrained Cartesian cut cell inversion to discern the maximum of information about HAJJAR deposit in order to calculate its tonnage. This article exhibits data and inversion processing technique for tonnage calculation based on an important geophysical magnetic and gravity surveys of defined extent of HAJJAR region, which presents a great benefit to save time and have accurate and realistic results to a same case. Otherwise, the potential-field signatures of what are regarded to be geologically expressive features are sought within the magnetic and gravity data. The preliminary stage for tonnage calculation was residual anomaly processing and depth estimation of the orebody using spectral analysis method. However, progressing towards extracting the deposit signature, the used method leads to invest the gravity signature of the orebody in adequacy with the magnetic signature. Finally, the tonnage calculation was developed by constrained Cartesian cut cell inversion using Voxi Earth ModellingTM. Obtained results were very important, given their qualitative and quantitative accuracy, which give an added value for the governmental geological and geophysical survey.

CNNEDGEPOT: CNN based edge detection of 2D near surface potential field data

Downward continuation of potential field is a useful tool in the processing and interpretation of magnetic and gravity data, but its direct calculation in space or spectral domain is unstable even in the presence of a small level of the noise and consequently restricts its practical application. This paper introduces a new method that combines upward continuation, vertical gradient via smoothing filters (Tikhonov regularization or Gaussian filters) and an iterative method into a single scheme to improve the stability and accuracy of the downward continuation. The optimal interval of iteration numbers for our developed approach is estimated by analysing the correlation coefficient curve between consecutive iterations. Applications to synthetic and real magnetic data show that this method can yield a more stable downward continuation of potential field data.

In the search for hydrocarbons, geologists, geochemists and geophysicists work together on the scale of a sedimentary basin. They seek to identify a petroleum system in order to maximise the chances of finding an accumulation of hydrocarbons in a specific part of the subsoil. The exploration campaign in the Cuvette Centrale began in the 1950s with geological, geophysical, geochemical and drilling campaigns carried out by several foreign organisations, including the Belgian firm Remina. These campaigns provided key information about the petroleum systems. These include the presence of hydrocarbon showings and geological structures that may favour the formation, migration and trapping of hydrocarbons. The main aim of this work is to highlight the geological structures of major petroleum interest, while identifying the geological structures found in our study area, particularly in Blocks 1 and 24 in the central basin of the Democratic Republic of Congo, and their petroleum interest, based on the processing and interpretation of magnetic and gravity data. To better study our sedimentary basin, we used the method of regional-residual separation and variation of the Magnetic Field, we had to highlight the faults in different directions North-West towards the South-East, the collapse trenches localised in the North-East, the zones of uplift of Socle which today constitute the top of Inongo. As never done before, this study develops a structural reference model by integrating the analysis of Bouguer and magnetic anomalies. It aims to locate zones of source rock maturation, identify possible hydrocarbon migration paths and pinpoint geological structures conducive to hydrocarbon accumulation. The results, presented in map form, are a strategic tool for petroleum exploration and the analysis of regional tectonic dynamics. In particular, it provides an unprecedented and detailed geophysical record for Blocks 1 and 24 of the Cuvette Centrale, enabling a targeted and efficient assessment of petroleum potential.

Gravity and magnetic anomalies create because of the lateral change in density and susceptibility of rocks underneath a certain datum. Gravity data in the form of Bouguer anomaly map of Erbil plain is subjected to quantitative interpretation by means of 2-D modeling by the assistance of some magnetic data in the form of profiles. Magnetic anomalies were interpreted qualitatively because of lack of magnetic properties of rocks. Seven gravity profiles in different directions from the Bouguer map were chosen to construct geological models which satisfy the situation. The residual anomaly of each profile was obtained by hand smoothing technique. It is shown that the main gravity low is attributed to thick Neogene sediments which are thrown against the Paleogene sediments by two major NW-SE faults which give rise to a density contrast of 0.3 gm/cm 3 , while local anomalies were interpreted as reflections of local and shallow structures and depressions within the upper part of the Neogene sediments. The shallower anomalous bodies are less than two kilometers in depth while the main anomalous body of Erbil so-called trough reaches four kilometers in depth. Magnetic anomalies indicate both suprabasment and intrabasement anomalies. It is revealed that at least a part of the Pirmam anticline (NW of the Gomspan NE-SW trending fault) is underlain by basic igneous rocks in the basement.

The results of the study of the influence of the deep factor on the process of melting of the ice cover of the Arctic Ocean and the formation of dangerous natural phenomena are presented. The peculiarities of the structure of the earth’s crust contributing to the ice destruction are visualized based on the interpretation of anomalies of the magnetic field and gravity. Density and magnetic sections of the bottom structures are constructed taking into account seismic and seismological data. Two-dimensional density calculations of the Arctic crust density have been performed to detect fluid-saturated layers. Analysis of satellite observations of ice condition together with interpretation of gravity and magnetic data made it possible to identify natural phenomena of endogenous origin, caused by influence of thermo fluid flows of the earth’s crust. The study of annual and seasonal changes in the thickness of multiyear ice over the period 2007–2020 has shown that a decisive role in the thawing process is played by fluid-supplying channels of deep-seated fault zones. The role of an endogenous factor in the destruction of ice of different ages and in the emergence of dangerous phenomena in the areas of hydrate development has been revealed. This makes it possible to predict the localization of zones of variability in the thickness of multiyear ice, the nature of the destruction of its edges and reduce the risks of navigation.

A Late Jurassic mantle plume may have generated hotspot tracks on the North American plate and the Yucatan Penninsula tectonic block as the Gulf of Mexico opened (ca. 150 Ma). The tracks are identified from deep basement structural highs that have been mapped by integrating seismic refraction and gravity data. They are associated with high-amplitude, distinctive gravity anomalies that provide the basis for a kinematic reconstruction that restores the western ends of the hotspot tracks with a 20° clockwise rotation of the Yucatan block or almost one-half the total rotation required to open the Gulf of Mexico Basin. The duration of track generation is estimated to have been about 8–10 m.y. or almost one-half the total time required to open the Gulf of Mexico Basin. Prior to this rotation, extension of continental crust over a 10–12-m.y. interval was the result of approximately 22° of counterclockwise rotation and crustal thinning. Autochthonous salt appears to be confined to the continental flanks of the hotspot tracks, confirming that salt was deposited during continental extension and not after ocean floor had begun to form. A prominent gravity anomaly along the western boundary of the basin is interpreted to be produced by a marginal ridge, which was created along the ocean-continent transform boundary as the basin opened. The eastern flank of this marginal ridge and the northernmost, easternmost, and southernmost terminations of the hotspot tracks are interpreted to coincide with the oceanic-continental crustal boundary in the basin. Dale E. Bird consults in the oil- and gas-exploration industry as a potential fields specialist. Since 1981, his experience in the industry includes acquisition, processing, interpreting, and marketing geophysical data, including positions with Aerodat, World Geoscience, Marathon Oil Company, Digicon, and Aero Service. He earned a Ph.D. from the University of Houston in 2004, and his research interests are regional geology and tectonics and the integration and interpretation of gravity and magnetic data. He is a member of several local and international geological and geophysical societies.Kevin Burke has been a professor of geology in the University of Houston since 1983, having previously lived and worked in several parts of the world. His main research is in tectonics: The large-scale evolution of planetary lithospheres. His current interests include African and Asian geology and the derivation of large igneous provinces from the core-mantle boundary. Stuart A. Hall is a professor of geosciences specializing in the study of gravity and magnetic fields. He received a B.Sc.(honors) degree in physics from the University of Birmingham, United Kingdom (1968) and a Ph.D. in geophysics from the University of Newcastle-upon-Tyne, United Kingdom (1976). His current research interests are mainly focused on the use of geophysical data to investigate the development of small ocean basins and orogenic belts. He is a member of the Society of Exploration Geophysicists, American Geophysical Union, Royal Astronomical Society, and Sigma Xi Research Society. John F. Casey is a professor of geology and chair of the Department of Geosciences at the University of Houston specializing in structure, tectonics, and geochemisty. He received a B.A. degree in geology from the University of Pennsylvania in 1975 and a Ph.D. in geology with honors from the State University of New York, Albany, in 1980. His research has focused on the tectonics and geochemistry of midocean ridges, transform faults, and ophiolite-bearing orogenic belts.

Interpretation of gravity and magnetic data in a strip of 250 sq.km. over Lanji-Darekasa tract of Khairagarh basin has been attempted in order to delineate regional structures and controls of uranium mineralisation in the province. Magnetic map indicates three parallel east-west trending lineaments representing basic dykes cutting across the geologic fonnations. The orthogonally intersecting gravity and magnetic trends around Saheki (80° 31' : 21° 27' 30") reveal a tectonised zone favourable for uranium minelisation. Gravity low of the order of five milligals near Nimbanaka (21° 19' : 80° 31' ) suggests a sharp increase in the thickness of Bijli rhyolites. Based on observed gravity, magnetic data and the available surface geological information, the paper proposes a model for configuration of Khairagarh basin along Lat. 21° 25' between Parsori and Khairagarh. Maximum thickness for volcano-sedimentary pile filling the basin along this section is estimated to be around 2300m. The model also indicates possibility for the presence of a concealed high density formation (Pitepani Volcanics?) below Bortalao sandstones.

The faults detected from the regional seismic section and the interpretation of gravity and magnetic data in central Iraq were reviewed. The faults obtained from these three geophysical methods were traced to get a unified fault map for the study region. According to the fault distribution density characteristics, the study region was divided into three zones: High, intermediate, and low fault distribution density across the region. Major tectonic boundaries separate these zones. The tectonic boundaries in some locations coincide with the major faults traced in previous studies. The obtained tectonic map shows moderate faults distribution density region area with a width of 100km, which represents the West of Nukhaib region. It shows a high distribution density faulted region of east Al-Nakhib to the Ramadi- Karbala- Najaf axis. A comparison was made between the fault distribution density zones and the detected tectonic boundaries of the current study with the results of previous tectonic studies, particularly in the central part of Iraq. The later region is affected by the uplifted mantle uplifting mantle and has a relatively low crustal thickness, which causes the high faulting density in this region.

Extensive Quaternary glacial cover and a lack of dense geophysical data within the Cook Inlet basin (CIB) of south-central Alaska make locating and determining the geometry of the Border Ranges fault system (BRFS), a major feature of the Alaska-Aleutian forearc region, difficult. We use recently collected gravity data, available aeromagnetic data, and other geophysical information as constraints to develop plausible two-dimensional cross-section models that better image the BRFS and related geologic structures of the CIB. Our integrated models show a thick sequence of late Mesozoic sedimentary rocks and the Peninsular terrane basement (6–20 km depth) overlying a serpentinized body at a depth of 16–34 km. The late Mesozoic rocks and serpentinite are interpreted as possible sources of the south Alaska magnetic high over the CIB. The eastern boundaries of the CIB are characterized by gravity and magnetic highs of the emplaced Border Range ultramafic and mafic assemblages (BRUMA). Formation of the BRUMA may be related to the serpentinized rocks that composed a Jurassic oceanic arc. Our models constrain the BRFS as a structural boundary between the overthrusted BRUMA and the Chugach terrane to the east. The BRFS dips 50°–70° toward the west-northwest and extends to at least 15 km. The BRFS may penetrate steeply or shallowly to a form a décollement at greater depths. A model that includes underplated sediments at the base of the accretionary complex (12–40 km) is consistent with the observed gravity low over the Chugach Mountains (Chugach terrane). The underplating may be associated with the subducting and shortening of the Yakutat microplate in south-central Alaska.

Interpretation of gravity and magnetic data in the Phlegraean fields geothermal area, Naples, Italy

Magnetic and gravity data analysis of Rahat Volcanic Field, El-Madinah city, Saudi Arabia

The Hakata hot springs area is located in Fukuoka City, which is in the southwestern part of Japan. Gamma-ray and gravity surveys were conducted to understand the relationship between the low-temperature hydrothermal systems and geophysical data of the area. The depth of the reservoir basement, which was derived from gravity data, gradually deepens toward the east; it includes some steep depth gradients in the Hakata hot springs area. High intensities of gamma-rays were detected around these gradients. In addition, higher hot spring temperatures and flow rates can be observed in this area. These results indicate that some part of the level of the basement where the hot springs are concentrated is a part of the Kego Fault and is similar to the fracture zone created by past activities of the fault. Moreover, these steep depth gradients act as a path for hot spring water from the deeper side of the granitic body to the surface.

The paper defines the blind source separation (BSS) problem, demonstrates the mathematic model and conditions for its solving, and explains the uncertainty of its solving. The paper analyses the algorithm of independent component analysis (ICA), proving EFFICA more suitable for engineering data processing. The paper illustrates the application of EFFCIA to the gravity and magnetic data processing and simulated experiments. The results show the advantage of ICA application in denoising and extraction of weak signal over the traditional gravity and magnetic data processing, worth further research.

The geothermal prospect located at Gunung Endut was investigated in 1980s based onreconnaissance surveys, primarily on geological and geochemical aspects. Then in 2006 a gravitymeasurement with 247 stations was carried out. However, due to the distribution of the gravity station wasless than optimal, interpretation of gravity data was not suitable with the geological situation that supportgeothermal system. To ensure this, we have carried out a new gravity survey with 134 random stationsdistribution but remained concentrated on hot spring locations. Data from both measurements were processedby the same treatment starting from pre-processing with some standar corrections to obtain completeBouguer anomaly, then continue by filtering process to separate regional and residual gravity anomaly usingButterworth filter in a wavenumber domain. Residual gravity anomaly map obtained by random position ofstations is more resemble to the geological features developed in the prospect area. The contrast boundariesof the residual gravity anomaly value coincide with the fault-line structures recorded in the surface geologicaldata. This result is better when compared with previous measurements. This study shows that there is asignificant influence of the distribution pattern of the gravity stations which affects the conformity with thegeological data. Based on the new interpretation result, the structural features in the prospect area arecharacterized by the complex fault structures that intersected each other mainly close to the surfacemanifestations. This intersection area is expected to be an enhanced permeability zone so that thehydrothermal fluid can flow to the surface. The interpretation of new gravity data combined with the resultsof geochemical analysis can be used for more understanding of the geothermal system beneath GunungEndut prospect area.