Crustal structure in the Campanian region (Southern Apennines, Italy) from potential field modelling

AbstractWe present a 3D model of the main crustal boundaries beneath the Campanian region and the onshore and offshore surrounding areas, based on high-resolution potential field data. Our main objective is the definition of the main structural interfaces in the whole Campanian region from gravity and magnetic data, thanks to their ability to define them on a regional and continuous way. The complex morphology of the Mesozoic carbonate platform, which is fundamental to constrain the top of geothermal reservoir, was reconstructed by inverting the vertical gradient of gravity. We assumed local information from seismic models and boreholes to improve the model. We modeled the deep crustal structures by spectral analysis of Bouguer gravity and magnetic data. The inferred depth estimates indicate a shallow crystalline basement below the Tyrrhenian crust and the Apulian foreland and a significant depression beneath the Bradanic foredeep. The map of the Moho boundary shows a NE-SE verging trough below the Southern Apennine chain and two pronounced uplifts beneath the foreland and the Tyrrhenian crust. We also estimated the depth to the magnetic bottom, showing a thick magnetic crust below the mountain chain and shallow depths where the crustal heat flow is high. The models were compared with seismic sections along selected profiles; a good agreement was observed, despite of some inherent lower resolution for the gravity modelling from spectral methods. The regional covering and the continuity of our estimated crustal interfaces make it a new and valid reference for further geological, geophysical and geothermal studies, especially in areas such as northern and eastern Campania, where there is an incomplete geophysical and geological information.

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Automatic 3-D interpretation of potential field data using analytic signal derivatives

Geophysics ◽

10.1190/1.1444149 ◽

1997 ◽

Vol 62 (1) ◽

pp. 87-96 ◽

Cited By ~ 56

Author(s):

Nicole Debeglia ◽

Jacques Corpel

Keyword(s):

Signal Amplitude ◽

Vertical Gradient ◽

Analytic Signal ◽

Magnetic Data ◽

Practical Implementation ◽

Potential Field Data ◽

Gravity And Magnetic ◽

Second Derivatives ◽

Gravity And Magnetic Data ◽

Derivatives Of

A new method has been developed for the automatic and general interpretation of gravity and magnetic data. This technique, based on the analysis of 3-D analytic signal derivatives, involves as few assumptions as possible on the magnetization or density properties and on the geometry of the structures. It is therefore particularly well suited to preliminary interpretation and model initialization. Processing the derivatives of the analytic signal amplitude, instead of the original analytic signal amplitude, gives a more efficient separation of anomalies caused by close structures. Moreover, gravity and magnetic data can be taken into account by the same procedure merely through using the gravity vertical gradient. The main advantage of derivatives, however, is that any source geometry can be considered as the sum of only two types of model: contact and thin‐dike models. In a first step, depths are estimated using a double interpretation of the analytic signal amplitude function for these two basic models. Second, the most suitable solution is defined at each estimation location through analysis of the vertical and horizontal gradients. Practical implementation of the method involves accurate frequency‐domain algorithms for computing derivatives with an automatic control of noise effects by appropriate filtering and upward continuation operations. Tests on theoretical magnetic fields give good depth evaluations for derivative orders ranging from 0 to 3. For actual magnetic data with borehole controls, the first and second derivatives seem to provide the most satisfactory depth estimations.

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Gravity and magnetic data analysis based on Poisson wavelet-transforms

10.5194/egusphere-egu2020-872 ◽

2020 ◽

Author(s):

Kirill Kuznetsov ◽

Bulychev Andrey ◽

Ivan Lygin

Keyword(s):

Data Analysis ◽

Magnetic Fields ◽

Potential Field ◽

Wavelet Transforms ◽

Geophysical Methods ◽

Magnetic Data ◽

Potential Field Data ◽

Gravity And Magnetic ◽

Gravity And Magnetic Data ◽

Poisson Wavelets

Studies of the Earth&#8217;s interior structure are one of the most complex topics in modern science. Integration of different geophysical methods plays a key role in effectively tackling the problem. In the last decade capabilities of potential field geophysical methods have been increasing due to development of advanced digital technologies. Improved resolution and accuracy of gravity and magnetic fields measurements made by modern equipment makes it possible to build more detailed geological models. Different tectonic and structural elements being interpreted in such models produce potential field signals with different spectral characteristics. Like any geophysical signals, potential fields can be described as a spatially non-stationary signal. This means its frequency content may change depending on a given signal sample, in particular with different spatial location of a sample. In this case, approaches of gravity and magnetic fields analysis based on Fourier transform or signal decomposition into a number of harmonic functions can lead to incorrect results. One of the ways to solve this challenge involves using wavelet transform based algorithms, since these transforms do not assume stationary signals and each function of a wavelet-based basis is localized in space domain.In gravity and magnetic data analysis it is beneficial to use wavelets based on partial derivatives of the Poisson kernel, which correspond to derivatives of a point source gravity potential. Application of Poisson wavelets in potential field data analysis has begun in the 1990's and is predominantly aimed at studying gravity and magnetic fields singularity points during data interpretation.Similar to Fourier-based potential field techniques, it is possible to construct a number of data filtering algorithms based on Poisson wavelets. Current work demonstrates that it is possible to construct algorithms based on Poisson wavelets for transforming profile and spatially gridded gravity and magnetic data, e.g. for calculation of equivalent density and magnetization distributions, upward and downward continuations, reduction to pole and many other filters that take into account spatial distribution of the signal.Wavelet-transforms allow to account for spatially non-stationary nature of geophysical signals. Use of wavelet based techniques allows to effectively carry out potential field data interpretation in a variety of different geologic and tectonic settings in a consistent fashion.

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Preliminary Study on Fusion Scheme of Multi-dimensional and Multi-scale Potential Field Data

10.5194/egusphere-egu2020-6651 ◽

2020 ◽

Author(s):

Xiaolin Ji ◽

Wanyin Wang ◽

Fuxiang Liu ◽

Min Yang ◽

Shengqing Xiong ◽

...

Keyword(s):

Potential Field ◽

Field Data ◽

Gravity Data ◽

Magnetic Data ◽

Potential Field Data ◽

Multi Scale ◽

Gravity And Magnetic ◽

Different Dimensions ◽

Fusion Scheme ◽

Gravity And Magnetic Data

Gravity and magnetic surveys are widely used in geology exploration because of its advantages, such as efficient and economy, green and environment-friendly, widely coverage and strong horizontal resolution. In order to well study in the geology exploration, it is required to comprehensively combine the different scales (different scales data) and different dimensions (satellite data, aeronautical data, ground data, ocean data, well data, etc.) of gravity and magnetic data that were observed in different periods, however, the comprehensive application of the multi-dimensional and multi-scale gravity and magnetic data still stays in the initial stage. In this paper, we do research on the key point of the fusion of potential field data (gravity and magnetic data): the way to fuse the different scales and different dimensions of potential field data into a benchmark and the same surface. Based on this research, we propose a scheme to fuse the multi-dimensional and multi-scale gravity and magnetic data. The synthetic models show that this fusion scheme is able to fuse the multi-dimensional and multi-scale gravity and magnetic data with great fusion results and small errors, in addition, the most important is that the fusion data conform to the characteristics of the potential field data and can meet the needs of data processing in the following steps. One of case studies in China has been accomplished to fuse aeronautical and ground gravity data that are different scales by using this fusion scheme. The fusion scheme we proposed in this study can be used in the fusion of the multi-dimensional (aeronautical, ground and ocean) and multi-scale gravity and magnetic data, which is good for interpretation and popularization.

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An improved terracing algorithm for potential-field data

Geophysics ◽

10.1190/geo2019-0129.1 ◽

2020 ◽

Vol 85 (5) ◽

pp. G109-G113

Author(s):

G. R. J. Cooper

Keyword(s):

Potential Field ◽

Field Data ◽

Shape Index ◽

Magnetic Data ◽

Threshold Parameter ◽

Potential Field Data ◽

Gravity And Magnetic ◽

Realistic Result ◽

Geologic Map ◽

Gravity And Magnetic Data

Although the boundaries between geologic units with different physical properties are usually quite distinct, the potential-field anomalies associated with them are relatively smooth, particularly for deeper bodies. The terracing filter has been introduced to sharpen anomaly edges and to produce regions of constant amplitude between them, mimicking geologic units on a geologic map. The boundaries between the pseudogeologic units are defined by the zero contour of the Laplacian function. Unfortunately, this can result in the domains of terraced anomalies extending far from the original location of the causative body, producing an image that poorly represents the geology. I have determined that the use of the mathematical shape index of the anomalies, rather than their Laplacian, produces a much more geologically realistic result. The effect can be controlled as desired using a threshold parameter. I evaluate the benefits of the method on gravity and magnetic data from southern Africa.

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Petroleum potential of the offshore southern Carnarvon Basin—insights from new Geoscience Australia data

The APPEA Journal ◽

10.1071/aj10126 ◽

2011 ◽

Vol 51 (2) ◽

pp. 746

Author(s):

Irina Borissova ◽

Gabriel Nelson

Keyword(s):

Seismic Data ◽

Source Rocks ◽

Magnetic Data ◽

Long Distance ◽

Potential Field Data ◽

Petroleum Potential ◽

Gravity And Magnetic ◽

Gravity And Magnetic Data ◽

Insight Into ◽

Carnarvon Basin

In 2008–9, under the Offshore Energy Security Program, Geoscience Australia (GA) acquired 650 km of seismic data, more than 3,000 km of gravity and magnetic data, and, dredge samples in the southern Carnarvon Basin. This area comprises the Paleozoic Bernier Platform and southern part of the Mesozoic Exmouth Sub-basin. The new seismic and potential field data provide a new insight into the structure and sediment thickness of the deepwater southernmost part of the Exmouth Sub-basin. Mesozoic depocentres correspond to a linear gravity low, in water depths between 1,000–2,000 m and contain between 2–3 sec (TWT) of sediments. They form a string of en-echelon northeast-southwest oriented depressions bounded by shallow-dipping faults. Seismic data indicates that these depocentres extend south to at least 24°S, where they become more shallow and overprinted by volcanics. Potential plays in this part of the Exmouth Sub-basin may include fluvio-deltaic Triassic sandstone and Lower–Middle Jurassic claystone source rocks sealed by the regional Early Cretaceous Muderong shale. On the adjoining Bernier Platform, minor oil shows in the Silurian and Devonian intervals at Pendock–1a indicate the presence of a Paleozoic petroleum system. Ordovician fluvio-deltaic sandstones sealed by the Silurian age marine shales, Devonian reef complexes and Miocene inversion anticlines are identified as potential plays. Long-distance migration may contribute to the formation of additional plays close to the boundary between the two provinces. With a range of both Mesozoic and Paleozoic plays, this under-explored region may have a significant hydrocarbon potential.

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3-D inversion of gravity and magnetic data with depth resolution

Geophysics ◽

10.1190/1.1444550 ◽

1999 ◽

Vol 64 (2) ◽

pp. 452-460 ◽

Cited By ~ 62

Author(s):

Maurizio Fedi ◽

Antonio Rapolla

Keyword(s):

Potential Field ◽

Field Data ◽

Vertical Direction ◽

Depth Resolution ◽

Magnetic Data ◽

Data Set ◽

Potential Field Data ◽

Magnetic Methods ◽

Level Data ◽

Gravity And Magnetic

Magnetization and density models with depth resolution are obtained by solving an inverse problem based on a 3-D set of potential field data. Such a data set is built from information on vertical and horizontal variations of the magnetic or gravity field. The a priori information consists of delimiting a source region and subdividing it in a set of blocks. In this case, the information related to a set of field data along the vertical direction is not generally redundant and is decisive in giving a depth resolution to the gravity and magnetic methods. Because of this depth resolution, which derives solely from the potential field data, an unconstrained and joint inversion of a multiobservation‐level data set is shown to provide surprising results for error‐free synthetic data. On the contrary, a single‐observation level data inversion produces an incorrect and too shallow model. Hence, a good depth resolution is likely to occur for the gravity and magnetic methods when based on the information along the vertical direction. This is also evidenced by an analysis of the kernel function versus the field altitude level and by a singular value analysis of the inversion operators for both the single and multilevel cases. Errors connected to numerical upward continuation do not affect the quality of the solution, provided that the data set extent is larger than that of the anomaly field. Application of the method to a 3-D magnetic data set relative to Vesuvius indicates that the method may significantly improve interpretation of potential fields.

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ACLAS — A method to define geologically significant lineaments from potential-field data

Geophysics ◽

10.1190/geo2016-0337.1 ◽

2017 ◽

Vol 82 (4) ◽

pp. G87-G100 ◽

Cited By ~ 1

Author(s):

Lorenzo Cascone ◽

Chris Green ◽

Simon Campbell ◽

Ahmed Salem ◽

Derek Fairhead

Keyword(s):

Large Scale ◽

Magnetic Data ◽

Data Set ◽

New Approach ◽

Potential Field Data ◽

North West ◽

Gravity And Magnetic ◽

Lineament Analysis ◽

The Individual ◽

Gravity And Magnetic Data

Geologic features, such as faults, dikes, and contacts appear as lineaments in gravity and magnetic data. The automated coherent lineament analysis and selection (ACLAS) method is a new approach to automatically compare and combine sets of lineaments or edges derived from two or more existing enhancement techniques applied to the same gravity or magnetic data set. ACLAS can be applied to the results of any edge-detection algorithms and overcomes discrepancies between techniques to generate a coherent set of detected lineaments, which can be more reliably incorporated into geologic interpretation. We have determined that the method increases spatial accuracy, removes artifacts not related to real edges, increases stability, and is quick to implement and execute. The direction of lower density or susceptibility can also be automatically determined, representing, for example, the downthrown side of a fault. We have evaluated ACLAS on magnetic anomalies calculated from a simple slab model and from a synthetic continental margin model with noise added to the result. The approach helps us to identify and discount artifacts of the different techniques, although the success of the combination is limited by the appropriateness of the individual techniques and their inherent assumptions. ACLAS has been applied separately to gravity and magnetic data from the Australian North West Shelf; displaying results from the two data sets together helps in the appreciation of similarities and differences between gravity and magnetic results and indicates the application of the new approach to large-scale structural mapping. Future developments could include refinement of depth estimates for ACLAS lineaments.

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Interpretation of gravity and magnetic data from southwestern Newfoundland and their correlation with Lithoprobe East seismic lines 89-11 and 89-12

Canadian Journal of Earth Sciences ◽

10.1139/e94-080 ◽

1994 ◽

Vol 31 (6) ◽

pp. 881-890

Author(s):

R. Wiseman ◽

Hugh G. Miller

Keyword(s):

Vertical Gradient ◽

Magnetic Data ◽

Reflection Data ◽

Gravity And Magnetic ◽

Magnetic Modelling ◽

Dimensional Gravity ◽

A Minor ◽

Seismic Reflection Profiles ◽

Gravity And Magnetic Data ◽

Gravity And Magnetic Anomaly

Several Newfoundland Appalachian terranes converge in the southwest corner of the island. The recent Lithoprobe East deep seismic reflection profiles imaged the crust along a transect across this area. In this paper, we present the gravity and magnetic data for the area and process them using shaded relief, horizontal and vertical gradient, upward continuation, and layer stripping techniques to interpret the more subtle features of the fields.Traditional two and one-half dimensional gravity and magnetic modelling is undertaken using constraints from the reflection data to develop a model of the crust in this region. The results from the processing are then used to interpret the crustal structure away from the seismic line.In general, we find that the major features on the gravity and magnetic anomaly maps can be explained by sources in the upper crust. The major faults in the area bound terranes that differ in potential field character. A minor change to the location of one terrane boundary is suggested. The rest correlate well with the geophysical data.

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COMPUTER MODELING IN GRAVITY AND MAGNETIC INTERPRETATION

Geophysics ◽

10.1190/1.1440873 ◽

1978 ◽

Vol 43 (5) ◽

pp. 912-929 ◽

Cited By ~ 16

Author(s):

B. K. Bhattacharyya

Keyword(s):

Potential Field ◽

Magnetic Data ◽

Arbitrary Distribution ◽

Potential Field Data ◽

Gravity And Magnetic ◽

Gravity Fields ◽

Anomalous Gravity ◽

Iterative Procedures ◽

First Vertical Derivative ◽

Gravity And Magnetic Interpretation

Computation of anomalous gravity and magnetic fields generated by various models is a necessary step if techniques of curve‐matching are to be used for quantitative interpretation of potential field data. Recently developed methods show that anomalous magnetic and gravity fields are completely determined by the divergence of magnetization and the first vertical derivative of density, respectively. Using these methods, efficient algorithms can be developed for computing potential field anomalies caused by arbitrary distribution of magnetization and density in an irregularly shaped body. Automatic iterative procedures are normally employed in the space domain for estimating parameters of the selected model that yield a best‐fit anomaly curve for a set of discrete observed data. Examples of application of the Newton‐Raphson method, Marquardt method, and the Powell algorithm to the interpretation of magnetic data are presented and discussed. Amplitude and energy spectra of the anomalous fields are also used conveniently in many cases for systematic estimation of average and individual depths, horizontal and vertical extents, and density or magnetization contrasts of causative bodies in a bounded region. Some of these frequency‐domain approaches are found to have many useful applications.

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Homomorphic deconvolution of potential field data in one and two dimensions

Canadian Journal of Earth Sciences ◽

10.1139/e83-112 ◽

1983 ◽

Vol 20 (8) ◽

pp. 1260-1281 ◽

Cited By ~ 2

Author(s):

Oliver G. Jensen ◽

Pandelis P. Papazis

Keyword(s):

Potential Field ◽

Field Data ◽

Seismic Analysis ◽

Geological Structure ◽

Two Dimensions ◽

Magnetic Data ◽

Wave Form ◽

Potential Field Data ◽

Gravity And Magnetic ◽

Geophysical Measurement

A signal in a non-dispersive reverberent environment can generally be represented as the sum of overlapping delayed replicas of a basic wave form. This convolutional data model has long been employed in seismic analysis and can be usefully extended for the analysis of gravity and magnetic potential field data along with a host of other geophysical measurements. The deconvolution of gravity or magnetic data requires the separation of two basic components of the potential fields: one component represents a basic irreducible wave form or signature of the potential field, and the other represents the position and scale or distribution of this wave form throughout the area of measurement. The basic wave form often derives from the process of geophysical measurement (e.g., the upward-continuation operator) but may also be due to an inherent, common character of the geological structure of an area.Oppenheim obtained the formalism for a generalized theory of superposition that allows for a description of the deconvolution process in terms of non-linear homomorphic transformations. These methods have already found application in the geophysical analysis of seismic data; it now provides a useful tool for the deconvolution of geophysical potential field data.

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