Upward continuation of potential fields has been used by geophysicists for many years as a means of smoothing data before interpretation. Despite its widespread use, no systematic investigations have been conducted regarding the optimal selection of the continuation height for noise suppression. In this paper, we provide a model study on the upward continuation height. We also consider the effect of the upward continuation height on the edge detection result. Through synthetic examples and a field example from the Tarija basin, South America, we assess how different continuation heights affect the results of the exponential transform of the tilt angle of the horizontal gradient (ETAHG). The results indicate that, when the upward continuation height is less than or equal to twice the grid spacing for gravity data, or less than or equal to five times the grid spacing for magnetic data, the results remain comparable to those at the observation plane. However, in the case of gravity data, the continuation height should not exceed five times the grid spacing, whereas for magnetic data, whose anomalies usually have a higher resolution, it should remain below ten times the grid spacing. The findings based on real data show that the ETAHG result for upward continuation data at 3.6 km is not only smooth but also accurately represents the geological structures of the Tarija basin. This map displays NW-SE trending lineaments, reflecting the dominant tectonic shortening direction during the Andean orogeny. In addition, many new structural features have been determined, providing a better understanding of the basin’s structural and tectonic framework.

The geological structures of the An Chau trough have been studied since the 70s of the last century, yet most previous work has focused on surface geology, leaving its subsurface structural framework poorly understood. In this research, we apply the upward-downward continuation filter to the magnetic data of the An Chau structure to reduce noise. Then, some edge detection methods that are less dependent on the magnetization direction are used to interpret the filtered magnetic data. The obtained results from our calculations provide a wide range of magnetic lineaments, which are not observed in the subsurface geological map of the trough. The depth of these lineaments is also determined using some semi-automatic methods, revealing that most magnetization sources in the area are of shallow depths, less than 4 km. Our analysis also demonstrates that the region is dominated by the ENE-WSW oriented trend. A new structural map is also established from our magnetic interpretations, which may suggest a possible structural relationship between the An Chau trough and the southern region of the Youjiang basin in the South China Block. Our findings offer a clearer view of the structural characteristics of the study area, addressing gaps in the knowledge of its tectonic and geological framework.

The crustal structure and gold fields of the Asir and Jiddah terranes in the Makkah region of the Arabian Shield are examined using a comprehensive methodology that integrates Landsat-8 imagery with gravity and magnetic data. An Enhanced Horizontal Gradient Amplitude (EHGA) filter helps identify the structures controlling the gold mineralization. The region is primarily characterized by the Ad Damm and Fatima fault zones, which are mylonitic dextral shear zones exhibiting flexural slip folding and a thrust duplex system. Various structural orientations distinguish the Asir and Jiddah terranes, including NW, NE, N-S to NNE, E-W, and WNW trends. Deeper structural features generally follow the same trends, with some shifts toward N-S and NE-to-ENE directions. The study covers gold fields such as As Suq, Ar Rjum, Ad Duwayhi, and Shaab Al Taare, where mineralization is influenced by E-W and N-S trending structures. The crust thickness (Moho interface) in the Makkah area varies from 25 to 46 km. The region has undergone three major deformation phases, with the youngest event being the most intense, producing folds, faults, and fractures. These results offer new insights into the tectonic architecture and structural framework of the Arabian Shield in this area and enhance the understanding of the geodynamic processes and crustal formation shaping Asir and Jiddah terranes.

Methods for potential field enhancement and parameter estimation routinely employ horizontal and vertical derivatives. Several regularization methods have been proposed for the latter, which is typically calculated in the wavenumber domain and is more sensitive to noise. We propose a finite-difference formula to compute horizontal derivatives that has the same theoretical accuracy as the standard centered-difference formula, but involves upward-continued data only, thus reducing noise amplification. The upward continuation height is chosen from local minima of C-norm curves of the horizontal derivatives, as in Tikhonov regularization methods. We illustrate the proposed calculation by comparing standard and stabilized maps of the total horizontal gradient, as well as other edge-detection filters applied to synthetic and real datasets. The enhancement maps obtained using the proposed approach are sharper than those using the standard approach, even when the data are previously filtered by upward continuation.

Methods for enhancing and estimating parameters of potential fields from gravimetric and magnetometric surveys typically utilize the vertical derivative (VDR) of the potential field. These derivatives amplify the high-frequency content of the field, which can be caused by shallow bodies or survey noise. Regularization methods generate approximations of derivatives that must reconcile two objectives: reducing the effect of high-frequency amplification and providing an accurate approximation. Achieving this balance is crucial for methods that require vertical derivatives of successive order, such as Taylor-series implementations of downward continuation and the enhanced horizontal derivative (EHD) filter. This paper evaluates the performance of several vertical-derivative methods for downward continuation and EHD filters using both noise-free and noisy synthetic data. In addition, gravity data over the SW Sub-basin are considered, and the findings are compared with seismic data. Our results show that the β-VDR method provides more accurate and stable derivatives under noisy conditions.

Vertical derivatives play an important role in qualitative and quantitative interpretations of potential fields. Nevertheless, the common methods are not stable in the presence of noise. In this study, a new method based on upward continuation data and Taylor series expansion to perform stable vertical derivatives was introduced. Unlike previous methods, the presented method used only upward continuation data, which made it less sensitive to noise while still providing vertical derivatives at the observed plane. The presented method was tested on synthetic data and field data from the Vredefort impact structure, South Africa. In the synthetic examples, the proposed method was more stable and accurate than other methods. In the real example, the findings showed that the vertical derivatives computed by the proposed method were also more stable, and the use of these derivatives in the enhanced horizontal derivative filter provided the linear structures more clearly than others.

This study analyzes satellite-derived gravimetric data from the XGM 2016 model to investigate the tectonic and structural framework of central Cameroon and to evaluate potential links with seismic hazards and vulnerability. Regional and residual components of the Bouguer anomaly were separated using 2D spectral analysis and a cosine filter with cut-off frequencies between 0.015 and 0.5 rad/ km, allowing the isolation of local signatures relevant for structural interpretation. A visual inspection of the residual gravimetric anomalies revealed various amplitude variations with abrupt changes, reflecting local heterogeneities in subsurface mass distribution. Advanced edge detection techniques, especially the Normalized Edge Detection (NED) and Fast Sigmoid Edge Detection (FSED) proved effective in delineating geological contacts and fault-related structures, supporting the interpretation of major subsurface boundaries. Euler deconvolution (SI = 1) constrained the depth of several lineaments, with most sources located between 13 and 18 km. Forward 2.5D gravity modeling, constrained by regional geology and seismic velocity models, suggests crustal heterogeneities involving possible gneissic and syenitic intrusions, localized upper-crustal thickening, and zones of deformation near major tectonic boundaries. These interpretations remain consistent with previously documented structures, including the Sanaga Shear Zone (SSZ), Central Cameroon Shear Zone (CCSZ), and the northern margin of the Congo Craton (CC). Finally, the spatial comparison between gravimetric lineaments, seismic events, population density, and road infrastructure highlights areas of potential vulnerability. The northern margin of the CC and the Cameroon Volcanic Line (CVL) emerge as priority zones, where crustal structures coincide with recorded earthquakes and highly urbanized, infrastructure-dependent regions. These results underscore the importance of integrated gravimetric, geological, and seismological approaches for assessing tectonic instability and seismic risk in Central Africa. (c) 2025 COSPAR. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

The Tu Chinh – Vung May (TC-VM) basin is one of the Cenozoic rift basins along the continental margin of Vietnam, formed during the tectonic evolution associated with the opening of the East Vietnam Sea (EVS). This paper addresses the scarcity of geophysical studies in the basin by using gravity anomalies to investigate its structural and tectonic characterization. Several edge enhancement techniques are estimated on a synthetic model before applying them to the Bouguer field of the basin. Bouguer data maps upward continued to different heights, and the corresponding results are also analyzed. Finally, the gravity inversion is used to map the Moho structure of the basin. The outcomes show that the enhanced horizontal gradient (EHG) filter yields sharper signals over the boundaries, and avoids bringing false edges; therefore, its outputs are used to establish a new subsurface structural map where many NNE-SSW, NE-SW, and N-S trending structures are recognized in the basin. The identified structural trends show a close correspondence with the orientations of the two major seafloor spreading stages of the EVS and may therefore reflect the influence of the regional tectonic regime associated with these spreading events. The inversion result shows that the Moho depth of the basin is approximately 9.7–22.4 km with a mean depth of 17 km, which is in agreement with the depth from seismic data. The findings demonstrate that the tectonic evolution of the TC-VM basin is closely tied to the broader geodynamic processes of the EVS, influenced by its sea-floor spreading and opening.

One of the important tasks in mapping geological structures is determining the horizontal boundaries of density structures. These boundaries can be estimated by using the edge detection techniques of gravity data. In this study, we apply several traditional edge enhancement filters along with recently developed techniques to the Bouguer gravity data to analyze structural trends and fault zones in the Ailaoshan Orogenic Belt, which is known as a significant suture zone between the South China Block and the Indochina Block. The edge recognition capabilities of these filters are examined using both noise-free and noisy synthetic gravity data before applying them to real gravity anomaly data of the belt. The structural features from the edge detection techniques are also confirmed by the Euler deconvolution method, where the result shows that the depth estimates in the Ailaoshan Orogenic Belt change from 0.9 to 4.7 km. The findings show that edge detection techniques produce anomaly maps that are well-correlated with the main tectonic framework of the study area, which trends NW-SE. These techniques are also helpful in identifying some structural features that are not visible at the surface, thus contributing to a more complete crustal framework of the Ailaoshan Orogenic Belt.

Detecting the source edges from potential field data is crucial in geological interpretations since it helps to identify contacts, faults, and other tectonic features. In recent years, many high-resolution filters have been introduced to generate sharp signals over the edges. In this study, we review 16 recent high-resolution filters, and introduce two frameworks for most of these filters. The filters are compared and discussed in terms of their accuracy and sharpness in detecting the edges using synthetic data. It is found that the filters based on the horizontal gradient are helpful in reducing the false information, while the filters using the second vertical derivative in the numerator can provide the edges with the highest resolution. The findings also show that the performance of many of the newer filters based on horizontal gradient or modified horizontal gradient versions is similar or lower compared to the previous horizontal gradient-based filters. Finally, we estimate and discuss the edges obtained from applying the filters to aeromagnetic data in the Montresor area (Canada), comparing the inferred edges with known geological structures. The obtained results demonstrate that the horizontal gradient-based filters are a useful tool for interpreting potential field data.

The stable downward continuation method can enhance low amplitude anomalies and improve the resolution of potential fields. However, this method may be affected by the edge effect. In this paper, we improve the downward continuation results by using the cubic Hermite interpolation to extend data. Our synthetic model shows that the proposed extension can provide better estimates, especially at the edges, than using constant values. We further enhance downward continued data using boundary filters where the boundaries obtained from the downward continued data have a higher resolution. The methods are also applied to interpret RTP magnetic and Bouguer gravity anomalies of the Central Highlands (Vietnam), where the RTP magnetic data are determined from the multiple-stage RTP method, while the Bouguer gravity data are calculated using the Parker formula. The spectral analysis of potential fields reveals the depth of shallow sources in the area of about 1 km, which determines the height of the downward continuation. A new subsurface structural map is established for the Central Highlands from the filtered results of downward continued data, which will be a helpful document for detailed future explorations and geology studies of the area.

The total horizontal gradient (THG) and its derivatives are commonly used in interpreting potential fields. Because THG is a nonharmonic function, its vertical derivative (VD) can be consistently computed using, e.g., a finite-difference approximation. The calculation of VD in the wavenumber domain is physically meaningful for harmonic functions, but it provides a pseudovertical derivative (PVD) when applied to nonharmonic fields that can be used in some edge detectors, such as THG. Through experiments with synthetic and field datasets, we evaluated the performance of the PVD of THG in the tilt angle of THG (TAHG) and fast sigmoid-based edge detector (FSED). TAHG and FSED are known as THG-based filters in mapping the edges of causative bodies. The results with synthetic data and magnetic data from the Montresor Belt (Canada) show that maps produced from the PVD of THG are clearer than those from the VD of THG near the source edges. Overall, the PVD of THG significantly enhances the edge detection of potential fields.

The Rub' Al-Khali Basin is one of the largest hydrocarbon producing basins in the world. Since the basin is covered by the Quaternary sand sea, its structural configuration is known only from geophysical data. In this study, we determine the structural lineaments and Moho structure of the basin from high resolution gravity data of the WGM2012 model using recently proposed techniques. The spectrum analysis is used to separate anomalies due to sources at different depth levels from Bouguer gravity data. The edge detection techniques are applied to these anomalies to extract the structural lineaments. In addition, the gravity inversion has been used with the purpose to estimate the Moho depth of the area. The obtained results revealed that most of the trends of shallow lineaments are N-S, W-E and NW-SE directions, the major lineament trend of average depth sources is N-S, while the deep lineaments compare favorably with features of the Moho structure. Our gravity inversion shows a thick crust in the southwest part and thinner in the northeast region. The Moho result consistents with seismic studies in the area, while gravity lineaments add local detail to the framework of the East African Orogen, where the N-S trends in the basin are broadly collinear with the dominant East African orogenic trends. This study provides detailed subsurface structures for a better knowledge of the tectonic evolution of the area.

Southwest Cameroon has long lacked detailed geological data, prompting an investigation into its geological and tectonic features through innovative edge detection techniques applied to gravity data. We employed various methods, including the Analytical Signal (AS), Tilt Angle (TDR), Total Horizontal Gradient of the Tilt Angle (TDR_THDR), and the Logistic Filter (IL) to delineate geological features that manifest as lineaments and contacts on gravity anomaly maps. Main findings of this study involve identification of key tectonic boundaries, notably the Kribi-Campo faults (KCF) and the Ebolowa pseudo-karstic circular network, the latter being mapped for the first time. This work reveals the continuity of the Ebolowa network and integrates connections such as the Mbilibekon and Mfuda caves, enhancing our understanding of the region's geological evolution. Additionally, we detailed the north-south extension of the KCF, which extends into both oceanic and terrestrial domains, aligning with the eastern margin of the Congo Craton. This finding suggests the fault system's role as a transition between the stable cratonic core and the dynamic mobile belts, necessitating a re-evaluation of regional tectonic models. To support our edge detection interpretations, we estimated Moho depths using gravity and seismic data, finding a Moho depth range between 34.5 km and 45.9 km, correlating with significant faulting and sedimentary features. This research enhances the understanding of subsurface structures in Southwestern Cameroon and provides a robust foundation for future geological and geophysical studies, emphasizing the critical interplay between surface and subsurface processes.

The tectonic and depositional history of the Hanoi basin is intricately shaped by the India-Eurasia collision, resulting in a complex subsurface structure that remains of significant interest for geophysical studies. In this research, classical and recent edge enhancement filters are applied to map subsurface features in the sediment-covered southern Hanoi basin. Additionally, the tilt-depth technique is employed to estimate the depth of subsurface structures in the study area. The interpretation revealed several subsurface structures, most of which have depths ranging from 0.9 km to 4 km. The subsurface features revealed by the enhancement filters show that the region’s structural trend is generally NW-SE, aligning with significant faults within the Red River fault zone, including the Song Chay and Song Lo. According to the tilt-depth estimates, the faults are identified at intermediate to deeper depths, reflecting geological displacements during the Oligocene and early Miocene that caused the Indochina geoblock to move about 700 km southeast along the Red River fault zone. Our detailed analysis also showed the Hanoi basin forms the landward extension of the Song Hong basin. The findings not only align with established tectonic features but also underscore the effectiveness of advanced filtering techniques, particularly the improved edge detector, in refining subsurface mapping within complex geological settings.

Accurate depth estimation is crucial for the quantitative interpretation of magnetic anomalies, which plays a significant role in geological mapping, mineral exploration and subsurface investigations. Traditional depth estimation techniques, such as the contact-depth (CD) and tilt-depth (TD) methods, often suffer from the generation of spurious solutions, especially when applied to complex geological environments. To address this, we propose an enhanced depth estimation technique, namely, the located contact-depth (LCD) method that integrates the CD technique with the enhanced horizontal gradient amplitude (EHGA). By utilizing points near the peaks of EHGA, a mask is generated to constrain the solutions from the CD method, effectively eliminating false solutions. Furthermore, a stable finite-difference technique for calculating vertical derivatives is used to improve the robustness and stability of the outputs. The proposed technique is tested on synthetic data, both with and without noise, as well as on real aeromagnetic data from the Galinge Fe-polymetallic deposit (China). The results demonstrate that our method provides depth estimates with improved reliability and accuracy compared to traditional methods, reducing the number of spurious solutions and enhancing precision around source boundaries. The result from the real example is in good agreement with known structures, highlighting the potential for deep mineral exploration in the Galinge Fe-polymetallic deposit.

Downward continuation is a very interesting approach to enhance the information content of potential field data. However, the calculation of the downward continuation represents a fundamental challenge due to its inherent instability. In this study, a strategy to perform high-order vertical derivatives using the β-VDR method is introduced, called the generalized β-VDR method. Testing on a noisy synthetic model shows that the proposed strategy has the lowest noise compared to other methods. Based on stable vertical derivatives computed by using the generalized β-VDR method, a stable downward continuation method is also presented to enhance the information content of potential field data. The applicability of the generalized β-VDR downward continuation algorithm is demonstrated on both synthetic and real field gravity anomalies and compared to other downward continuation algorithms. In the case of synthetic examples, the proposed method provides sharper images and estimates more accurate amplitudes than other algorithms, even continuing the field to a level close to causative bodies. The real application shows that the proposed algorithm can give a meaningful result that agrees well with seismic data along a profile in the area.

In the equatorial Atlantic Ocean, the Mid-Atlantic Ridge is offset by a set of major transform fault systems, including the Romanche, Chain, Charcot, St. Paul, Doldrums and Vema faults, which remain relatively poorly understood due to the lack of detailed geophysical and geological studies. This study aims to analyze in detail satellite gravity data of the Equatorial Atlantic Ridge (EAR) to improve our understanding of its geological setting. To achieve this, we use the tilt angle of the horizontal gradient, the horizontal gradient of the second tilt angle, the balanced horizontal gradient, and the improved tilt angle of the horizontal gradient methods to map the lineaments of the area, while the depth of density sources is computed using the Euler deconvolution algorithm. The findings demonstrate the dominance of the ENE-WSW oriented trend, and the gravity sources are in the depth range of from 1.8 to 8 km. These findings are not only in agreement with known discordant and fracture zones, but also provide information on newly identified boundaries in the EAR. (c) 2025 COSPAR. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

The exploration of hidden structures beneath complex tectonic regions using potential field edge detection techniques poses a significant challenge. Traditional edge enhancement methods encounter inherent limitations, such as generating low-resolution outcomes or heavily depending on source depth. To overcome these challenges, we introduced an innovative edge detector called the Enhanced Horizontal Gradient (EHG). Through thorough testing on synthetic models (both 2D and 3D), we evaluated its performance against other conventional edge enhancement techniques. Our results demonstrate that the proposed detector effectively generates clear signals along source boundaries, minimizes the introduction of false edges, and operates independently of source depth. Applying the EHG method to Bouguer gravity anomalies, in conjunction with prominent tectonic faults, suture zones, mantle Bouguer anomalies, and Moho structure, provides substantial insights into comprehending the gravity characteristics of the Central continental margin of Vietnam and adjacent areas. Key findings from our research encompass the identification of discontinuities in the Red River Fault Zone, the absence of the Tam Ky-Phuoc Son (TK-PS) fault, the mapping of the extension of the magmatic zone in the oceanic region toward the northeast part of the Phu Khanh Basin, and a noticeable shift in gravity trends from NNE-SSW in the northeastern region of the East Vietnam Sea (EVS) to NNW-SSE direction. Moreover, the Moho depth obtained from gravity inversion, ranging from 7 to 54 km in the study area, closely corresponds with the intricate tectonics, offering conclusive evidence of a mechanism involving the flow of crustal magmatic material and associated uplift. In conclusion, our study suggests that interactions among tectonic plates likely play a role in shaping complex tectonic settings and the underlying uplift mechanism, ultimately influencing changes in bathymetry and seafloor structure.