scholarly journals Mass anomaly visualisation and depth estimation from full tensor gradient gravity data

2013 ◽  
Vol 2013 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Daniel Wedge ◽  
Yathunanthan Sivarajah ◽  
Eun-Jung Holden ◽  
Peter Kovesi ◽  
Chris Wijns ◽  
...  
Keyword(s):  
Gravity Data ◽  
Depth Estimation

scholarly journals Gravity Analysis for Subsurface Characterization and Depth Estimation of Muda River Basin, Kedah, Peninsular Malaysia

2021 ◽  
Vol 11 (14) ◽  
pp. 6363
Author(s):  
Muhammad Noor Amin Zakariah ◽  
Norsyafina Roslan ◽  
Norasiah Sulaiman ◽  
Sean Cheong Heng Lee ◽  
Umar Hamzah ◽  
...  
Keyword(s):  
River Basin ◽  
Rock Type ◽  
Gravity Data ◽  
Power Spectral Analysis ◽  
Depth Estimation ◽  
Structural Features ◽  
Peninsular Malaysia ◽  
Gravity Survey ◽  
Basement Rock ◽  
Geophysical Techniques

Gravity survey is one of the passive geophysical techniques commonly used to delineate geological formations, especially in determining basement rock and the overlying deposit. Geologically, the study area is made up of thick quaternary alluvium deposited on top of the older basement rock. The Muda River basin constitutes, approximately, of more than 300 m of thick quaternary alluvium overlying the unknown basement rock type. Previous studies, including drilling and geo-electrical resistivity surveys, were conducted in the area but none of them managed to conclusively determine the basement rock type and depth precisely. Hence, a regional gravity survey was conducted to determine the thickness of the quaternary sediments prior to assessing the sustainability of the Muda River basin. Gravity readings were made at 347 gravity stations spaced at 3–5 km intervals using Scintrex CG-3 covering an area and a perimeter of 9000 km2 and 730 km, respectively. The gravity data were then conventionally reduced for drift, free air, latitude, Bouguer, and terrain corrections. These data were then consequently analyzed to generate Bouguer, regional and total horizontal derivative (THD) anomaly maps for qualitative and quantitative interpretations. The Bouguer gravity anomaly map shows low gravity values in the north-eastern part of the study area interpreted as representing the Main Range granitic body, while relatively higher gravity values observed in the south-western part are interpreted as representing sedimentary rocks of Semanggol and Mahang formations. Patterns observed in the THD anomaly and Euler deconvolution maps closely resembled the presence of structural features such as fault lineaments dominantly trending along NW-SE and NE-SW like the trends of topographic lineaments in the study area. Based on power spectral analysis of the gravity data, the average depth of shallow body, representing alluvium, and deep body, representing underlying rock formations, are 0.5 km and 1.2 km, respectively. The thickness of Quaternary sediment and the depth of sedimentary formation can be more precisely estimated by other geophysical techniques such as the seismic reflection survey.

Integration of magnetic, gravity, and well-logging data interpretation to delineate the structural framework and formation evaluation of Bahariya Formation, North Diyur area, northern Western Desert, Egypt

2021 ◽  
Vol 40 (10) ◽  
pp. 724-733
Author(s):  
Walaa Araby ◽  
Samy H. Abd ◽  
Alaa E. Aref ◽  
Ibrahim Al-Alfy ◽  
M. M. Abdullah ◽  
...  
Keyword(s):  
Structural Control ◽  
Water Saturation ◽  
Gravity Data ◽  
Depth Estimation ◽  
Well Logging ◽  
Western Desert ◽  
Gravity Modeling ◽  
Potential Field Data ◽  
Lithology Identification ◽  
Bahariya Formation

The Bahariya Formation in Egypt's Western Desert is a major source for minerals and hydrocarbon accumulation. It is also characterized by a relatively high radiation content because it contains iron oxide deposits that attract radioactive elements. The main objectives of our study are to establish depth to basement, basement configuration and related structural elements, and thickness and configuration of the overlain sedimentary section. In addition to the analysis of well-logging data, many advanced techniques have been applied to analyze magnetic and gravity data, including depth estimation, 2D magnetic and gravity modeling, and 3D inversion of potential field data. By integrating all available data, we can determine the structural control of the study area and evaluate the subsurface parameters. Well logging has been used for interpretation of porous and permeable zones, water saturation calculation, and basic lithology identification. The depth to basement in our study ranges from −1700 to −4500 m. The basement is shallow in the northern parts of the study area and deeper in the southern parts. The main clay minerals of the formation are montmorillonite, chlorite, and a mixed clay layer. The Bahariya Formation is composed mainly of sandy clay and sandstone, and therefore it is considered an excellent reservoir.

Weighted Euler deconvolution of gravity data

Geophysics ◽  
1998 ◽  
Vol 63 (5) ◽  
pp. 1595-1603 ◽  
Author(s):  
Pierre B. Keating
Keyword(s):  
Euler Equations ◽  
Gravity Data ◽  
Error Function ◽  
Bouguer Anomaly ◽  
Depth Estimation ◽  
Euler Deconvolution ◽  
Structural Index ◽  
Eastern Canada ◽  
Adequate Sampling

Euler deconvolution is used for rapid interpretation of magnetic and gravity data. It is particularly good at delineating contacts and rapid depth estimation. The quality of the depth estimation depends mostly on the choice of the proper structural index and adequate sampling of the data. The structural index is a function of the geometry of the causative bodies. For gravity surveys, station distribution is in general irregular, and the gravity field is aliased. This results in erroneous depth estimates. By weighting the Euler equations by an error function proportional to station accuracies and the interstation distance, it is possible to reject solutions resulting from aliasing of the field and less accurate measurements. The technique is demonstrated on Bouguer anomaly data from the Charlevoix region in eastern Canada.

scholarly journals Tensor deconvolution: A method to locate equivalent sources from full tensor gravity data

Geophysics ◽  
2007 ◽  
Vol 72 (5) ◽  
pp. I61-I69 ◽  
Author(s):  
Valentin Mikhailov ◽  
Gwendoline Pajot ◽  
Michel Diament ◽  
Antony Price
Keyword(s):  
Gravity Field ◽  
Gravity Data ◽  
Random Noise ◽  
Depth Estimation ◽  
Observation Point ◽  
Euler Deconvolution ◽  
Structural Index ◽  
Measuring Device ◽  
Equivalent Sources ◽  
Scalar Invariants

We present a method dedicated to the interpretation of full tensor (gravity) gradiometry (FTG) data called tensor deconvolution. It is especially designed to benefit from the simultaneous use of all the FTG components and of the gravity field. In particular, it uses tensor scalar invariants as a basis for source location. The invariant expressions involve all of the independent components of the tensor. This method is a tensor analog of Euler deconvolution, but has the following advantages compared to the conventional Euler deconvolution method: (1) It provides a solution at every observation point, without the use of a sliding window. (2) It determines the structural index automatically; as a consequence, the structural index follows the variations of the field morphology. (3) It uses all components of the measured full gradient tensor and gravity field, thus reducing errors caused by random noise. It is based on scalar invariants that are by nature insensitive to the orientation of the measuring device. We tested our method on both noise-free and noise-contaminated data. These tests show that tensor solutions cluster in the vicinity of the center of causative bodies, whereas Euler solutions better outline their edges. Hence, these methods should be combined for improved contouring and depth estimation. In addition, we use a clustering method to improve the selection of solutions, which proves advantageous when data are noisy or when signals from close causative bodies interfere.

scholarly journals Edge detection, depth estimation and 3D-inverse modelling of the Red Sea and Zagros gravity anomalies using the gravity data extracted from EGM2008 Geo-potential Model

2020 ◽  
Vol 50 (1) ◽  
pp. 1-32
Author(s):  
Ali AMJADI ◽  
Bahram AKASHE ◽  
Mohammad ARIAMANESH ◽  
Mohsen POURKERMANI
Keyword(s):  
Edge Detection ◽  
Red Sea ◽  
Gravity Data ◽  
Geophysical Methods ◽  
Gravity Anomalies ◽  
Depth Estimation ◽  
Inverse Modelling ◽  
Subsurface Structures ◽  
Detection Depth ◽  
Effective Depth

Using geophysical methods and measuring physical properties of subsurface rocks are good solutions for investigating the subsurface structures and exploring underground buried resources (such as oil, gas, water, minerals, etc.). This research investigates the anomaly sources of Zagros and the Red Sea by using the derivative filters, regularized filters, analytic signal, local-phase filter, 3D-inverse modelling with the Li-Oldenburg method. For this purpose, these filters are first applied to artificial models to determine the capability of each of these filters, a comparisons is also will be made between edge detection filters and finally applied to the real gravity of Zagros and Red Sea regions (taken from the EGM2008 Global Model). The overall result is that the effective depth of the sources of gravity anomalies of the Red Sea is approximately 200 km, and incoherently, up to a depth of 300 km. The effective depth of the Zagros anomalies sources is also about 180 km and since then it has continued inconsistently up to 400 km.

scholarly journals Space-frequency analysis and reduction of potential field ambiguity

1997 ◽  
Vol 40 (5) ◽  
Author(s):  
M. Fedi ◽  
A. Rapolla
Keyword(s):  
Potential Field ◽  
Phase Plane ◽  
Gravity Data ◽  
Depth Resolution ◽  
Depth Estimation ◽  
Vertical Axis ◽  
Local Power ◽  
Potential Field Data ◽  
Space Frequency ◽  
Inherent Ambiguity

Ambiguity of depth estimation of magnetic sources via spectral analysis can be reduced representing its field via a set of space-frequency atoms. This is obtained throughout a continuous wavelet transform using a Morlet analyzing wavelet. In the phase-plane representation even a weak contribution related to deep-seated sources is clearly distinguished with respect a more intense effect of a shallow source, also in the presence of a strong noise. Furthermore, a new concept of local power spectrum allows the depth to both the sources to be correctly interpreted. Neither result can be provided by standard Fourier analysis. Another method is proposed to reduce ambiguity by inversion of potential field data lying along the vertical axis. This method allows a depth resolution to gravity or the magnetic methods and below some conditions helps to reduce their inherent ambiguity. Unlike the case of monopoles, inversion of a vertical profile of gravity data above a cubic source gives correct results for the cube side and density.

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