Euler Deconvolution Method Research Articles

Effective combination of microgravimetry and geoelectrical methods in the detection of subsurface cavities in archaeological prospection – selected case-studies from Slovakia

Abstract This contribution is focused on a common utilization of microgravimetry (very precise and detailed gravimetry) and geoeletrical methods (ground penetrating radar and electric resistivity tomography) in the detection of subsurface cavities in non-destructive archaeological prospection. Both methods can separately detect such kind of subsurface objects, but their complementary and at the same time an eliminating aspect can be very helpful in the interpretation of archaeogeophysical datasets. These properties were shown in various published case-studies. Here we present some more typical examples. Beside this, we present here for a first time an application of the electric resistivity tomography in the interior of a building (a church) in Slovakia. We also demonstrate an example with an extremely small acquisition step in microgravity as a trial for the detection of cavities with very small dimensions – in this case small separated spaces for coffins as a part of the detected crypt (so called columbarium). Unfortunately, these cavities were too small to be reliably detected by the microgravity method. We have tried the well-known 3D Euler deconvolution method to obtain usable depth estimates from the acquired anomalous gravity field. Results from this method were in the majority of cases plausible (sometimes little bit too shallow), when compared with the results from the ground penetrating radar. In one selected example, the 3D Euler solutions were too deep and in the present stage of study we cannot well explain this situation. In general, all presented results support an important role of common combination of several geophysical methods, when searching for subsurface cavities in non-destructive archaeological prospection.

Distribution of subsurface anomalies in the Muria Peninsula and depth analysis with euler deconvolution

Muria Peninsula is one of the regions in Central Java that is uniquely formed. The Muria Peninsula was originally separated from Java and is now connected. To complement the studies that have been done before, subsurface analysis using euler deconvolution method is carried out. Gravity data used is satellite data provided free by BGI. The results of the processing produced a residual anomaly which showed a fault that passed in the middle of the peak of Muria towards Mount Genuk. The anomaly depth of Mt. Muria is 1000 m to 2000 m, in the peak area of Muria and Genuk <1000 m, and in the east and west of the study area the anomaly depth is more than 2000 m. Euler deconvolution index 0 illustrates the body boundaries of Mt. Muria and Genuk in the form of dike and steep.

Identification of oil and gas bearing objects using geophysical data in the eastern part of the Gulf of Suez, Egypt

The airborne magnetic data is considered as one of the best methods to delineate the depth to basement layer. The airborne magnetic survey data obtained from the Egyptian Nuclear Materials Authority. Data is accurately processed, interpreted. Two-dimensional (2D) modeling was performed by GM-SYS, along one selected profile yielded from RTP map. In addition to that, three-dimensional (3D) Euler Deconvolution method was performed to delineate the depth to basement layer. Euler solutions were applied on RTP Grid by structural indexes 0, 1, 2, and 3 to select the best solution. The sedimentary succession of the study area is created using seismic data and well data. Petroleum system model was established to predict the locations of hydrocarbons within the study area. The results of PetroMod confirmed that the area is very promising for hydrocarbon aggregations, and also new hydrocarbon aggregations have been discovered.

Estimating the location of a causative body from a self-potential anomaly using 2D and 3D normalized full gradient and Euler deconvolution

Changes in the size and depth of sources greatly affect self-potential (SP) anomalies. Therefore, it is important to determine the location of the source accurately. In the present study, applications of the normalized full gradient (NFG) method and Euler deconvolution (EUD) were described to determine the location of the sphere-like SP body as complementary approaches to other optimization algorithms. The NFG and EUD methods were tested on synthetic, noise-free, and noisy anomalies caused by sphere-like models in two-dimensional (2D) and three-dimensional (3D) cases. Subsequently, the methods were applied to real field data. The importance of the present study lies in the fact that it is the first 3D application of these methods to the SP anomaly caused by the sphere-like model in the literature. In order to determine the optimum harmonic number in the NFG method, a new criterion was used instead of the usual trial-and-error method, providing more reliable selection possibilities. In a similar way, average values were used to determine the window size accurately in the EUD method. The test results of the synthetic and real field models were satisfactory. They showed that both methods are applicable to determine the location of sphere-like structures, such as ore deposits, in self-potential surveys.

A combined Euler deconvolution and tilt angle method for interpretation of magnetic data in the South region

Introduction: The purpose of this paper is to determinate the position, depth, dip direction and dip angle the faults in the South region of Vietnam from the total magnetic intensity anomalies, that reduced to the magnetic pole (RTP).
 Methods: Based on the Oasis Montaj software, we proposed a new way to compute the positions and the depth to the top of the faults by combining the Tilt angle and the Euler deconvolution methods. In addition, the angle and direction of the dip of theses faults were also determined by considering maximum of the total horizontal derivative of the RTP upward continuation at the different height levels.
 Results: The results show that there are 12 faults along the longitudinal direction, latitudinal direction, Northwest — Southeast direction and Northeast — Southwest direction with the mazimum depth is about 3100 m and the dip angle changes in the range of 65-82◦.
 Results: These indicate that these methods are valuable tools for specifying the characteristics of geology, contribute to give and confirm the useful information on geological structure in the South region of Vietnam.

Comparative depth estimation of iron-ore deposit using the Data-Coordinate Interpolation Technique for airborne and ground magnetic survey variation

A newly developed quantitative method, Data-Coordinate Interpolation Technique (DCIT) was used by matching the secondary and primary data to correct the variation that exists between airborne and ground magnetic depth-to-basement. The aeromagnetic data within latitude (8.000N, 8.500N) and longitude (4.000E, 4.500E) were acquired and gridded, while the in-situ location are Ajase (8.19520, 8.19720 N), (4.38800 E, 4.39000 E) and Gbede (8.29200 N, 8.29360 N), (4.34620 E, 4.34760 E). Aeromagnetic data were contoured at airborne to ground spacing ratio and data interpolation was done on the contour to produce a set of interpolated data. Quantitative analysis was done using Peter’s Half slope Method (PHSM), Analytic Signal Method (ASM) and Euler Deconvolution Method (EDM) to calculate the depth-to-top of the iron-ore within the basement complex. Results at Ajase for depth for DCIT and ground data were 6.47 ± 2.28 m, 5.79 ± 1.81 m; 5.55 ± 2.90 m, 5.53 ± 1.90 m; and 7.88 ± 1.52 m, 8.75 ± 1.47 m, respectively. At Gbede, the results were 6.16 ± 2.09 m, 5.34 ± 1.50 m; 5.79 ± 2.07 m, 5.66 ± 1.75 m; and 5.95 ± 1.59 m, 5.74 ± 0.88 m, respectively. The average depths at Gbede with respect to DCIT and ground data were 5.97 ± 1.92 m, 5.58 ± 1.38 m and Ajase, 6.63 ± 2.23 m and 6.69 ± 1.73 m, respectively. Comparatively, the variation in the depth estimates for both airborne and ground magnetic data is minimal with DCIT.

Estimating the location of magnetic sources using magnetic gradient tensor data

In this paper, a new method for the interpretation of magnetic sources is developed using magnetic gradient tensor data. The total magnetisation direction of each magnetic source is estimated, and the magnetic gradient tensor is transformed into tensor data, which would be produced by the same sources with vertical magnetisation. Furthermore, the horizontal edges of the broad steep-sided magnetic sources are estimated from the ratio of the sum of absolute values of the eigenvalues (SAE) and Bzz of the transformed magnetic gradient tensor. The depth estimation of the magnetic sources is obtained using a modified Euler deconvolution method that eliminates the structural index from the equations. The process was tested on both synthetic and measured magnetic data. The results show that this method reduces considerably the effects of total magnetisation and is tolerant to the noise of the data. In addition, this method calculates vertical locations without any prior information about the structural index of the source.

Geophysical study of Ubiaja and Illushi area in northern Anambra basin, Nigeria, using combined interpretation methods of aeromagnetic data

The aeromagnetic data of Ubiaja and Illushi area which falls within latitude 6°30′N–7°00′N and longitude 6°00′N–7°00′E were qualitatively and quantitatively interpreted. The qualitative interpretation revealed that the area is intensely faulted with major anomalies (faults) trending in the northeast and southwest directions. Standard Euler deconvolution, source parameter imaging (SPI) and modeling (forward and inverse) methods were employed in the quantitative interpretation. The aim of the quantitative interpretation includes determination of the thickness of the sedimentary basin, magnetic susceptibilities and possible type of mineralization prevalent in the area. The SPI depth result ranges from − 258.2 to − 3497.7 m. The depth result from standard Euler deconvolution method for the structural index SI = 0.5 ranges from 1377.3 to − 2510.9 m; for SI = 1, the depth to magnetic sources ranges from 1482.0 to − 3003.3 m; for SI = 2, the depth to magnetic sources range from 1627.8 to − 2984. 3 m; and for SI = 3, the depth ranges from 1853.9 to − 3089.9 m. The results from forward and inverse modeling for profiles 1, 2, 3 and 4 showed depths of − 4118 m, − 3611 m, − 2964 m and − 5489 m, respectively (− signs signify subsurface depth). The susceptibility values of 0.0100 obtained for profiles 1 and 2 are associated with group of minerals such as hematite, gneiss, granite or gabbro. Profile 3 with susceptibility value of 0.0613 is typical of igneous rock porphyry. Profile 4 with susceptibility value of 0.0288 depicts minerals such as slate and hematite.

Interpretation of gravity data using 3D inversion and 2D continuous wavelet transform in Hedil deformed structures, northern Tunisia

The Hedil region in northern Tunisia shows several geological structures associated with intense tectonic deformations that induced genesis of overthrusts and tectonic imbrications with rising of Triassic evaporites. This region constitutes a transition zone, between the Atlassic and Tellian domains, and exhibits multi-scale tectonic deformations related to the basins structure and the regional geodynamic of the Northern African margin. Gravity data processing and continuous wavelet transform, coupled with field data, lead to underline the subsurface geometric configuration and to propose an evolutionary structural framework for the studied area.The horizontal gradient magnitude (HGM) and its maxima highlight several lineaments trending NE-, E−, NW and N however the NE-SW direction is predominantly expressed. Depths of the main buried structures were estimated using the Euler deconvolution method. The highest values that exceed 3 km seem to underlines the structures associated to NE-SW, NW-SE and rarely E-W inherited features. The NE-SW oriented structures are mainly represented by overthrusts and tectonic imbrication zones that were occurred along inherited faults in the southern part of the area, as a result of the Atlassic compressional tectonics of Late Miocene and Quaternary ages. However the other lineaments correspond mainly to strike-slip and reverse. The application of 3D inversion method allows identification and characterization of geological structures in subsurface. The most deformed structures are marked by positive anomalies and are sometimes underlined by intrusion of Triassic evaporite rocks. However, the collapsed structures are underlined by negative anomalies testifying a material of low density. The extracted inversion sections highlight the deep rooted geometry of the Triassic bodies, locally associated with overturn of pierced strata.The continuous wavelet transform method was used to get an idea about the deep structures of the region, to estimate the boundary between the sedimentary filling and the Precambrian basement, and determining the depth and dipping of some identified contacts. Some uplifted structures and Triassic evaporite intrusions especially that of the Bazina are marked by risings of pre-Triassic deep causative sources. These zones of significant anomalies in the Atlassic domain are probably areas of intense deformation related to the ancient Hercynian tectonics that affected the North African margin. The identified structures should be related to the regional tectonic inversion, related to the African and European plates subduction.

Investigating edge detection, Curie point depth and heat flow using EMAG2 magnetic and EGM08 gravity data in northern part of Eastern Anatolia, Turkey

The edge detection, the Curie point depths (CPDs), and the heat flow in the northern part of Eastern Anatolia were examined using EMAG2 magnetic and EGM08 Bouguer gravity data. Edge detection methods are extensively employed to delineate the edges of sources using potential field data. In the study area, the tilt angle, total horizontal derivative, theta map, and 3D Euler deconvolution methods were used to delineate the subsurface geology and heterogeneity. The 3D Euler deconvolution method was carried out to determine the depth of the subsurface magnetic and gravity anomalies. The Euler depth solutions show that the depths range from 0 to 15 km for the Bouguer gravity anomalies, while the depths vary from 0 to 16 km for the magnetic anomalies. In this study area, the CPD values vary between 15.7 km and 18.6 km. For a thermal conductivity of 2.5 W m-1 K-1, the heat flow values were determined to be between 75 and 95 mW m-2. A plot of CPDs versus heat flow values revealed an exponential correlation between heat flow and CPD values. A good relationship was detected between the CPDs and the heat flow values.

English

Aeromagnetic data over Abakaliki area of lower Benue trough, Nigeria was interpreted qualitatively and quantitatively using Oasis montaj software. The qualitative interpretation unveiled basic intrusive bodies like dykes, laccolites and batholitic bodies in the area. It also revealed fault zone which trends southeastern part of the study area. Quantitative interpretation was carried out by forward and inverse modeling, source parameter imaging and Euler deconvolution methods. Depth obtained by source parameter imaging (SPI) ranged from 99.50 to 5930.78 m. Results from this study indicate that deep seated bodies are predominant in the southwestern part of the area, while shallow bodies are predominant in the southeastern part of the area. The anomalies over the area were modeled by bodies in the form of sphere and ellipsoid by varying the total magnetic intensity parameters. Depth obtained by model A is 546 m with susceptibility value of 0.0180 signifying limestone. The height of Model B is 50 m signifying outcrop, likely to be the outcrop near college of Agricultural Sciences of Ebonyi State University, Abakaliki, with susceptibility value of -0.0017 signifying calcite. Depth obtained for models C, D and E are 956, 6366 and 477 m respectively, with respective susceptibility values of -0.0134, -0.009 and -0.006 signifying rock salt, quartz and Calcite. Maximum depth obtained by forward and inverse modeling is 6366m while that obtained by source parameter imaging is 5930.78 m. Key words: Abakaliki area, aeromagnetic anomalies, qualitative and quantitative interpretation, intrusive bodies, hydrocarbon accumulation.

Mapping of Deep Tectonic Structures of Central and Southern Cameroon by an Interpretation of Surface and Satellite Magnetic Data

The aim of this study is to determine the depth of deep tectonic structures observed in the Adamawa-Yadé zone (central part of Cameroon) and propose a new structural map of this area. The horizontal gradient associated with upward continuation and the 3D Euler deconvolution methods have been applied to the Earth Magnetic Anomaly Grid 2 (EMAG2) data from the study area. The determination of the maximum magnitude of the horizontal gradient of the total magnetic intensity field reduced to the equator, in addition to the main contacts deducted by Euler solution, allowed the production of a structural map to show the fault systems for the survey area. This result reveals the existence of two structural domains which is thus confirmed by the contrast of magnetic susceptibility in the Central Cameroon Zone. The suggested depths are in the range of 3.34 km to 4.63 km. The structural map shows two types of faults (minors and majors) with W-E, N-S, NW-SE, NE-SW, ENE-WSW, WNW-ESE, NNE-SSW, and NNW-SSE trending. The major faults which are deepest (3.81 km to 4.63 km) with NE-SW, W-E, and N-S direction are very represented in the second domain which includes the Pangar-Djerem zone. This domain which recovers many localities (Ngaoundéré, Tibati, Ngaoundal, Yoko Bétaré-Oya, and Yaoundé) is associated with the Pan-African orogeny and the Cameroon Volcanic Line.

Usefulness of electrical and magnetic methods in finding buried structure of the Alabanda Ancient Cistern in Çine Town, Aydın City, Turkey

In this paper, the Electrical Resistivity Tomography and magnetic methods, including Tilt Angle and Euler Deconvolution, have been used in a comperative manner to determine the lineaments and depths of buried archeological structures. The zero contours of the tilt angle correspond to the boundaries of buried structures and the half distance between ±π/4 rad corresponds to the depth to the top of the structures. Also, in order to estimate the positions and depths of buried structures in the study area, the Euler Deconvolution method was applied to the total magnetic field data. All of the methods have a good correlation about determination of the horizontal locations and depths of the buried structures. The archeological excavations based on the geophysical investigations have demonstrated that the buried structure is an ancient cistern building because of the unearthed pools. Therefore, the interpretations of the geophysical methods and fiction of the paper were made according to the ancient cistern building. With this study, a buried ancient cistern structure was modeled and revealed by the geophysical methods for the first time. Additionally, using of these geophysical techniques in a comparative manner for the archaeogeophysical work will greatly contribute to future studies.

Geophysical mapping of buried faults in parts of Bida Basin, North Central Nigeria

ABSTRACTHigh‐resolution aeromagnetic data over the Bida Basin, North Central Nigeria has been analysed to investigate the possible continuity of Ifewara fault zone, through the Bida Basin, to Zungeru fault zone. Analytic signal magnitude, horizontal gradient magnitude, and Euler deconvolution methods were applied to the aeromagnetic data to delineate the subsurface structures. The results showed that a prominent NNE–SSW trending fault associated with the Ifewara fault zone extends through the study area. Other faults trending in the ENE–WSW, NE–SW, NW–SE, E–W, and WNW–ESE directions were also mapped. Interpreted models revealed the presence of intrusives and a possible mineralised zone within the study area. We therefore concluded that the inferred fault zones within the basin have affinity with the trend of the Ifewara fault zone, which is an indication of possible extension and linkage with Zungeru fault zone through the Bida Basin.

Interpretation of high resolution airborne magnetic data (HRAMD) of Ilesha and its environs, Southwest Nigeria, using Euler deconvolution method

Abstract Interpretation of high resolution aeromagnetic data of Ilesha and its environs within the basement complex of the geological setting of Southwestern Nigeria was carried out in the study. The study area is delimited by geographic latitudes 7°30′–8°00′N and longitudes 4°30′–5°00′E. This investigation was carried out using Euler deconvolution on filtered digitised total magnetic data (Sheet Number 243) to delineate geological structures within the area under consideration. The digitised airborne magnetic data acquired in 2009 were obtained from the archives of the Nigeria Geological Survey Agency (NGSA). The airborne magnetic data were filtered, processed and enhanced; the resultant data were subjected to qualitative and quantitative magnetic interpretation, geometry and depth weighting analyses across the study area using Euler deconvolution filter control file in Oasis Montag software. Total magnetic intensity distribution in the field ranged from –77.7 to 139.7 nT. Total magnetic field intensities reveal high-magnitude magnetic intensity values (high-amplitude anomaly) and magnetic low intensities (low-amplitude magnetic anomaly) in the area under consideration. The study area is characterised with high intensity correlated with lithological variation in the basement. The sharp contrast is enhanced due to the sharp contrast in magnetic intensity between the magnetic susceptibilities of the crystalline and sedimentary rocks. The reduced-to-equator (RTE) map is characterised by high frequencies, short wavelengths, small size, weak intensity, sharp low amplitude and nearly irregular shaped anomalies, which may due to near-surface sources, such as shallow geologic units and cultural features. Euler deconvolution solution indicates a generally undulating basement, with a depth ranging from −500 to 1000 m. The Euler deconvolution results show that the basement relief is generally gentle and flat, lying within the basement terrain.

Continuous wavelet transform and Euler deconvolution method and their application to magnetic field data of Jharia coalfield, India

Abstract. This paper deals with the application of continuous wavelet transform (CWT) and Euler deconvolution methods to estimate the source depth using magnetic anomalies. These methods are utilized mainly to focus on the fundamental issue of mapping the major coal seam and locating tectonic lineaments. The main aim of the study is to locate and characterize the source of the magnetic field by transferring the data into an auxiliary space by CWT. The method has been tested on several synthetic source anomalies and finally applied to magnetic field data from Jharia coalfield, India. Using magnetic field data, the mean depth of causative sources points out the different lithospheric depth over the study region. Also, it is inferred that there are two faults, namely the northern boundary fault and the southern boundary fault, which have an orientation in the northeastern and southeastern direction respectively. Moreover, the central part of the region is more faulted and folded than the other parts and has sediment thickness of about 2.4 km. The methods give mean depth of the causative sources without any a priori information, which can be used as an initial model in any inversion algorithm.

Geophysical investigation of the possible extension of Ifewara fault zone beyond Ilesa area, southwestern Nigeria

High-resolution aeromagnetic data (HRAD) of parts of the southwestern and north-central Nigeria between 7° 30′ N – 8° 30′ N and 4° 30′ E – 5° 30′ E have been analyzed with a view to investigate the possible extension of Ifewara fault zone beyond Ilesa area. Analyses of the filtered HRAD by analytic signal amplitude (ASA), horizontal gradient magnitude (HGM), first vertical derivative (FVD), and Euler deconvolution (ED) methods were combined to delineate the locations, strikes, and dip directions of the subsurface structures in the area. The inferred structural map and the associated rose diagram indicate that the area is bisected by a number of major and minor faults that trend NE-SW, ENE-WSW, E-W, NW-SE, WNW-ESE, NNE-SSW, and NNW-SSE, among which the NE-SW trending faults predominate. The Ifewara and other major fault zones were clearly delineated. The mapped Ifewara faults trend between NNE-SSW and NE-SW directions and extend from the southwestern part (Ilesa area) to the extreme of north-eastern part of the study area. The study concluded that the Ifewara fault zones exist and do not terminate in the southwestern part of Nigeria but further extends to the northern part, possibly to Nupe basin and Zungeru area.

Curie Point Depth, Geothermal Gradient and Heat-Flow Estimation and Geothermal Anomaly Exploration from Integrated Analysis of Aeromagnetic and Gravity Data on the Sabalan Area, NW Iran

Prospecting the geothermal resources in northwest of Iran, conducted in 1975, revealed several promising areas and introduced the Sabalan geothermal field as a priority for further studies. The Sabalan Mt., representing the Sabalan geothermal field, is a large stratovolcano which consists of an extensive central edifice built on a probable tectonic horst of underlying intrusive and effusive volcanic rocks. In this study, Curie point depth (CPD), geothermal gradient and heat-flow map were constituted from spectral analysis of the aeromagnetic data for the NW of Iran. The top of the geothermal resource (i.e., the thickness of the overburden) was evaluated by applying the Euler deconvolution method on the residual gravity data. The thickness of the geothermal resource was calculated by subtracting the Euler depths obtained from the CPDs in the geothermal anomalous region. The geothermal anomalous region was defined by the heat-flow value greater than 150 mW/m2. CPDs in the investigated area are found between 8.8 km in the Sabalan geothermal field and 14.1 in the northeast. The results showed that the geothermal gradient is higher than 62 °C/km and the heat-flow is higher than 152 mW/m2 for the geothermal manifestation region; the thickness of the geothermal resource was also estimated to vary between 5.4 and 9.1 km. These results are consistent with the drilling and other geological information. Findings indicate that the CDPs agree with earthquake distribution and the type of thermal spring is related to the depth of the top of the geothermal resource.

Field source characteristic of gravity variation in Hexi region before Menyuan Ms6.4 earthquake based on the Euler deconvolution

This study adopted the Euler deconvolution method to conduct an inversion and interpretation of the depth and spatial distribution pattern of field source that lead to gravity variation. For this purpose, mobile gravity data from four periods in the Hexi region between 2011 and 2015 were obtained from an observation network. With a newly established theoretical model, we acquired the optimum inversion parameters and conducted calculation and analysis with the actual data. The results indicate that one is the appropriate value of the structure index for the inversion of the mobile gravity data. The inversion results of the actual data showed a comparable spatial distribution of the field source and a consistent structural trend with observations from the Qilian-Haiyuan Fault zone between 2011 and 2015. The distribution was in a blocking state at the epicenter of the Menyuan earthquake in 2016. Our quantitative study of the field source provides new insights into the inversion and interpretation of signals of mobile gravity variation.

Interpretation of the magnetic data from Shavaz iron ore using enhanced local wavenumber (ELW) and comparison with Euler deconvolution method

This paper presents an inversion method for the interpretation of 2D magnetic anomaly data, in which uses the enhanced local wavenumber function to estimate the depth and the nature (structural index) of an isolated magnetic source. However, the method is sensitive to noise. In order to lower the effect of noise, I applied upward continuation technique to smooth the anomaly. Tests on synthetic noise-free and noise-corrupted magnetic data show that the method can successfully estimate the depth and the nature of the causative source. The practical application of the technique is applied to measured magnetic anomaly data from Shavaz Iron Ore, center of Iran, and the inversion results are in agreement with the inversion results from Euler deconvolution of the analytic signal and exploratory drilling.