Euler Deconvolution Method Research Articles

Determination of the parameters of compact ferro-metallic objects with transforms of magnitude magnetic anomalies

The transforms based on magnitude of the magnetic anomaly (MMA), or absolute value of anomalous magnetic intensity, are relatively insensitive to the direction of the source magnetisation vector and show high centricity. Obtaining them requires calculation of only first-order horizontal derivatives of the component magnetic anomalies X, Y and Z, obtained through transformation of total magnetic anomalies Δ T (TMA). We studied the use of the magnetic transforms based on the MMA of a dipole source and that of their ratios for determining the geometric and physical parameters of compact environmental ferro-metallic sources. Analytical formulas for all the parameters of the magnetic dipole based on calculation of MMAs, their gradients and Laplacian, and their ratios were obtained. The horizontal position of the dipole source is determined by the maximum of the Laplacian of the MMA, which is the transform with the highest centricity. We applied the approach on model data and on magnetic anomalies over environmental sources, represented by unexploded ordnance (UXO) and clutter from the Badlands Bombing Range, USA. The obtained parameter values were compared with those estimated through Euler deconvolution using unprescribed structural index and linear model of the background, and through inversion. The comparison showed that the proposed method produced similar depth results to that of the Euler deconvolution method for the objects with estimated structural index over and around 2.5, i.e., for the sources, which to a great extent can be approximated with a dipole. The inversion for the dipole parameters using as initial parameters the estimated with the MMA transform method ones confirmed the results of the MMA transform method for the dipole coordinates and magnetisation for all items.

A combined analytic signal and Euler method (AN‐EUL) for automatic interpretation of magnetic data

We present a new automatic method of interpretation of magnetic data, called AN‐EUL (pronounced “an oil”). The derivation is based on a combination of the analytic signal and the Euler deconvolution methods. With AN‐EUL, both the location and the approximate geometry of a magnetic source can be deduced. The method is tested using theoretical simulations with different magnetic models placed at different depths with respect to the observation height. In all cases, the method estimated the locations and the approximate geometries of the sources. The method is tested further using ground magnetic data acquired above a shallow geological dike whose source parameters are known from drill logs, and also from airborne magnetic data measured over a known ferrometallic object. In both these cases, the method correctly estimated the locations and the nature of these sources.

Imaging magnetic sources using Euler's equation

ABSTRACTThe conventional Euler deconvolution method has the advantage of being independent of magnetization parameters in locating magnetic sources and estimating their corresponding depths. However, this method has the disadvantage that a suitable structural index must be chosen, which may cause spatial diffusion of the Euler solutions and bias in the estimation of depths to the magnetic sources. This problem becomes more serious when interfering anomalies exist. The interpretation of the Euler depth solutions is effectively related to the model adopted, and different models may have different structural indices. Therefore, I suggest a combined inversion for the structural index and the source location from the Euler deconvolution, by using only the derivatives of the magnetic anomalies. This approach considerably reduces the diffusion problem of the location and depth solutions. Consequently, by averaging the clustered solutions satisfying a given criterion for the solutions, we can image the depths and attributes (or types) of the causative magnetic sources. Magnetic anomalies acquired offshore northern Taiwan are used to test the applicability of the proposed method.

Site Characterization by Geophysical Methods in The Archaeological Zone of Teotihuacan, Mexico

In the present investigation, a geophysical study was carried out in the eastern flank of the Pyramid of the Sun to define potential continuations in this direction of a tunnel discovered beneath the western main entrance of this building. This man-made structure is one of the many extraction tunnels hollowed by the ancient Teotihuacans to obtain construction materials to build their city. Total field and high-resolution vertical gradient magnetic surveys were carried out. The spectral analysis of the total magnetic field enabled us to estimate the thickness of the alluvial cover over the basaltic flow as 3·3m. It was also found that the main contribution to the observed magnetic field comes from the pyroclastic flow that covers the area of study. The horizontal gradient filter was applied to the low-pass filtered magnetic field to enhance magnetic contacts and structural boundaries. Inferred magnetic trends were related to fracture patterns within the basalts and pyroclasts, and low gradients provided an evidence of voids or tunnels. The Euler deconvolution method was applied as an attempt to confirm the above results. Using a structural index S=0, we determined the boundaries of main magnetic contacts as well as the interface between the basaltic flow and Las Varillas tunnel. Euler depths were found to range between 3 to 6m, which represent the mean thickness of the basaltic flow.Two parallel ground probing radar (GPR) profiles were surveyed in the NW-SE direction. One passes on top of the known location of a tunnel (Las Varillas) and a second one 10m to the north, approximately. The tunnel's roof is well outlined at depths between 3·5 and 4m. On the other hand, little evidences of other buried tunnels or extensions of the known one were found. The second profile depicts a more complex morphology for the pyroclastic sheet. Anomalies related to basaltic flow or eruptive centres are clearly observed. Both profiles depicted the sedimentary base at 3m, on average. A resistivity profile was undertaken along the first GPR profile. A resistivity image was obtained, that showed the vertical and lateral distribution of the true resistivity. High resistivity values were associated with the tunnel location (Las Varillas). Its geometry could also be inferred, its top is found at about 4m and extends 20m in the profile direction to the west. Unfortunately, the depth to its base could not be estimated, since profile length was too short. The sediment-pyroclastic flow interface could also be delimited at a depth of 3m.Finally, a vertical magnetic field profile taken along the same surveyed line (GPR and resistivity) was inverted applying a two-dimensional algorithm. The initial model was estimated from GPR and resistivity interpretations. A simple model of Las Varillas tunnel was computed, which reasonably well satisfied geological and geophysical considerations.

Euler deconvolution of gravity tensor gradient data

Tensor Euler deconvolution has been developed to help interpret gravity tensor gradient data in terms of 3-D subsurface geological structure. Two forms of Euler deconvolution have been used in this study: conventional Euler deconvolution using three gradients of the vertical component of the gravity vector and tensor Euler deconvolution using all tensor gradients. These methods have been tested on point, prism, and cylindrical mass models using line and gridded data forms. The methods were then applied to measured gravity tensor gradient data for the Eugene Island area of the Gulf of Mexico using gridded and ungridded data forms. The results from the model and measured data show significantly improved performance of the tensor Euler deconvolution method, which exploits all measured tensor gradients and hence provides additional constraints on the Euler solutions.

Three‐dimensional Euler deconvolution and tectonic interpretation of marine magnetic anomaly data in the Puerto Rico Trench

During the summer of 1996 single‐channel‐seismic, magnetic, gravity, Hydrosweep bathymetric and HMR1 sidescan data were collected north of the island of Puerto Rico to constrain the geologic and tectonic setting of the Puerto Rico trench. Magnetic data from this cruise are merged with other available data, then processed and interpreted with the aid of the Euler deconvolution method. The area north of the island of Puerto Rico is divided into three magnetic anomaly zones. Zone 1 is dominated by northwest to southeast trending magnetic anomalies. Zone 2 consists of an east‐west region of relatively low amplitude anomalies and occurs south of zone 1. Zone 3 is dominated by the highest magnetic values in the study area and the source region is roughly centered under the island of Puerto Rico. Respectively, these zones approximate three geologic provinces of the Puerto Rico trench composed of Early Cretaceous ocean crust with sedimentary cover, a blueschist belt and an Oligocene‐Cretaceous island arc with a limestone cap. Also mapped are the Main Ridge fracture zone and the Fourth of July fracture zone, both on the North American plate, which correlate with the Main Ridge and Fourth of July Ridge on the Caribbean plate. The 3‐D Euler deconvolution facilitates the identification of new faults as well as the mapping of known faults also evident in the seismic and bathymetric data. A model concerning the formation of the Puerto Rico trench is proposed that incorporates the existence of strike‐slip faults and the fracture zones associated with the subduction of the North America Plate. Evidence from this study support a tectonic interpretation of subduction followed by more recent strike‐slip faulting that is accompanied by only a minimal amount of subduction.

Euler deconvolution methods used to determine the depth to archaeological features

Abstract Field techniques, instrumentation and data processing for geophysical location of archaeological remains are now at such a standard that clear maps of the subsurface detail are readily obtainable. Magnetic gradiometry and resistivity plots are widely used to locate diverse features such as walls, ditches and burial areas. However, information concerning the depth to these features is not often extracted from such plots and would be useful in planning any following excavation. Here we use Euler deconvolution methods, on a reasonably high-resolution magnetic gradiometer data set, to determine the depth to a buried Romano-British villa at the Wroxeter archaeological site. The interpretation of these depth estimates is compared to GPR sections taken over the same site.

The application of microgravity in industrial archaeology: an example from the Williamson tunnels, Edge Hill, Liverpool

Abstract This article presents the results of a high-resolution microgravity survey which was successful in delineating the 150-year old Williamson tunnels beneath inner-city Liverpool, England. The tunnels, which date from the Napoleonic Wars, lie at depths of c. 5 to 15 metres, and are poorly mapped because of several phases of later development and subsequent dereliction. The ‘brown-field’ nature of this site created substantial noise signals which required the application of careful terrain corrections and second derivative and Euler deconvolution methods to isolate and identify the tunnel signatures. Successful delineation was only possible because of a comprehensive initial desk study and prior modelling, which assessed the likely depths and conditions of the impassable tunnels and allowed appropriate techniques and survey parameters to be determined.

Interpretation of the regional gravity and magnetic surveys of Wales, using shaded relief and Euler deconvolution techniques

AbstractRegional gravity and aeromagnetic data of Wales have been processed using a variety of techniques. Image processing has greatly assisted qualitative interpretation, whilst automated procedures have provided additional quantitative information. The shaded relief images emphasize gradients in the potential fields, and are useful for displaying strong linear features. The Euler deconvolution method produces plotted solution maps, which define the position of the source of the gravity and magnetic anomalies. Euler solution maps of Wales and the adjacent continental shelf are presented for the first time. These maps are interpreted in relation to the known geology, with special emphasis on the Lower Palaeozoic Welsh Basin. It is proposed that the Euler solutions define a network of fault-bounded blocks within the Precambrian basement.