AN APPROXIMATE SOLUTION OF THE PROBLEM OF MAXIMUM DEPTH IN GRAVITY INTERPRETATION

Geophysics ◽  
1963 ◽  
Vol 28 (5) ◽  
pp. 724-735 ◽  
Author(s):  
D. C. Skeels
Keyword(s):  
Approximate Solution ◽  
Gravity Anomaly ◽  
Maximum Depth ◽  
Actual Data ◽  
Density Contrast ◽  
Half Maximum ◽  
Gravity Interpretation ◽  
Best Fit

It is assumed that the maximum depth for the mass responsible for a given gravity anomaly is closely approximated by the depth to the top of the vertical‐sided mass (prism or cylinder, as the case may be) whose calculated anomaly gives the closest fit to the observed anomaly, and whose density contrast is the maximum permitted from geological considerations. A set of charts is presented by means of which the depth and dimensions of the prism (or cylinder) of “best fit” can be determined quickly from the amplitude, half‐maximum, and three‐quarter maximum widths of the anomaly, together with the assumed density contrast. Four examples are given of the use of the method with actual data.

Gravity interpretation using Fourier transforms and simple geometrical models with exponential density contrast

Geophysics ◽  
1993 ◽  
Vol 58 (8) ◽  
pp. 1074-1083 ◽  
Author(s):  
D. Bhaskara Rao ◽  
M. J. Prakash ◽  
N. Ramesh Babu
Keyword(s):  
Los Angeles ◽  
Fourier Transforms ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Sedimentary Basins ◽  
Density Contrast ◽  
Model Parameters ◽  
Exponential Density ◽  
Exponential Density Contrast ◽  
Gravity Interpretation

The decrease of density contrast in sedimentary basins can often be approximated by an exponential function. Theoretical Fourier transforms are derived for symmetric trapezoidal, vertical fault, vertical prism, syncline, and anticline models. This is desirable because there are no equivalent closed form solutions in the space domain for these models combined with an exponential density contrast. These transforms exhibit characteristic minima, maxima, and zero values, and hence graphical methods have been developed for interpretation of model parameters. After applying end corrections to improve the discrete transforms of observed gravity data, the transforms are interpreted for model parameters. This method is first tested on two synthetic models, then applied to gravity anomalies over the San Jacinto graben and Los Angeles basin.

On: “Gravity Interpretation Using the Fourier Integral”, by M. E. Odegard and J. W. Berg, Jr. (GEOPHYSICS, June 1965, p. 127–138)

Geophysics ◽  
1975 ◽  
Vol 40 (2) ◽  
pp. 356-357
Author(s):  
Jay Gopal Saha
Keyword(s):  
Fourier Transform ◽  
Gravity Anomaly ◽  
Fourier Integral ◽  
Two Dimensional ◽  
Transform Method ◽  
Reverse Problem ◽  
Vertical Fault ◽  
Vertical Step ◽  
The Fourier Transform ◽  
Gravity Interpretation

In their paper, Odegard and Berg claim that from the gravity anomaly due to a two‐dimensional vertical fault the density, the throw, and the depth can be determined uniquely by a Fourier transform method. It is true that the solution of the reverse problem for a two‐dimensional vertical step is theoretically unique. The derivation of the Fourier transform by the authors, however, is erroneous.

On: “The Gradational Density Contrast as a Gravity Interpretation Model” by D. J. Gendzwill (GEOPHYSICS, April 1970, p. 270–278)

Geophysics ◽  
1971 ◽  
Vol 36 (3) ◽  
pp. 618-618
Author(s):  
P. S. Naidu
Keyword(s):  
Gravity Field ◽  
Linear Density ◽  
Density Variation ◽  
Density Contrast ◽  
Simple Variation ◽  
Gravity Interpretation ◽  
Special Case ◽  
Interpretation Model

The author cites the following equation, from Novosolitskii (1965), giving the gravity field due to a slab where the density variation is along the x coordinate only, [Formula: see text] (1) and gives a solution for a special case of linear density variation over a limited zone. Even for such a simple variation, the expression is far too complicated.

Efficient gravity inversion of basement relief using a versatile modeling algorithm

Geophysics ◽  
2017 ◽  
Vol 82 (2) ◽  
pp. G23-G34 ◽  
Author(s):  
João B. C. Silva ◽  
Darcicléa F. Santos
Keyword(s):  
Gravity Anomaly ◽  
Region Of Interest ◽  
Sedimentary Basins ◽  
Density Contrast ◽  
Gravity Inversion ◽  
Deep Basin ◽  
Novel Approach ◽  
Green’S Operator ◽  
Translation Symmetry ◽  
Observation Position

We have developed a novel approach to compute, in an efficient and versatile way, the gravity anomaly produced by an arbitrary, discrete 3D distribution of density contrast. The method allows adjustable precision and is particularly suited for the interpretation of sedimentary basins. Because the gravity field decays with the square of the distance, we use a discrete Green’s operator that may be made much smaller than the whole study area. For irregularly positioned observations, this discrete Green’s operator must be computed just at the first iteration, and because each of its horizontal layers presents a center of symmetry, only one-eighth of its total elements need to be calculated. Furthermore, for gridded data on a plane, this operator develops translation symmetry for the whole region of interest and has to be computed just once for a single arbitrary observation position. The gravity anomaly is obtained as the product of this small operator by any arbitrary density contrast distribution in a convolution-like operation. We use the proposed modeling to estimate the basement relief of a [Formula: see text] basin with density contrast varying along [Formula: see text] only using a smaller Green’s operator at all iterations. The median of the absolute differences between relief estimates, using the small and a large operator (the latter covering the whole basin) has been approximately 9 m for a 3.6 km deep basin. We also successfully inverted the anomaly of a simulated basin with density contrast varying laterally and vertically, and a real anomaly produced by a steeply dipping basement. The proposed modeling is very fast. For 10,000 observations gridded on a plane, the inversion using the proposed approach for irregularly spaced data is two orders of magnitude faster than using an analytically derived fitting, and this ratio increases enormously with the number of observations.

Regional‐residual gravity anomaly separation using the minimum‐curvature technique

Geophysics ◽  
1991 ◽  
Vol 56 (2) ◽  
pp. 279-283 ◽  
Author(s):  
K. L. Mickus ◽  
C. L. V. Aiken ◽  
W. D. Kennedy
Keyword(s):  
Gravity Anomaly ◽  
Gravity Anomalies ◽  
Bouguer Gravity ◽  
Bouguer Gravity Anomaly ◽  
Residual Gravity ◽  
Residual Gravity Anomaly ◽  
Gravity Interpretation ◽  
Minimum Curvature

One of the most difficult problems in gravity interpretation is the separation of regional and residual gravity anomalies from the Bouguer gravity anomaly. This study discusses the application of the minimum‐curvature method to determine the regional and residual gravity anomalies.

THE VALUE OF QUANTITATIVE INTERPRETATION OF GRAVITY DATA

Geophysics ◽  
1942 ◽  
Vol 7 (4) ◽  
pp. 345-353 ◽  
Author(s):  
D. C. Skeels
Keyword(s):  
Gravity Anomaly ◽  
Gravity Data ◽  
Actual Data ◽  
Quantitative Interpretation ◽  
Geological Data ◽  
Unique Interpretation

Although there is no unique interpretation of a given set of gravity data, there are many cases in which quantitative interpretation is decidedly worthwhile. This is especially true in cases where the gravity data are supplemented by a certain amount of geological data, or where the gravity anomaly is of such a shape that the range of possible solutions can be rather closely limited. Three examples are given of interpretations of actual data.

scholarly journals Analysis of gravity anomaly and seismicity in Bali region

2021 ◽  
Vol 5 (3) ◽  
pp. 34-43
Author(s):  
Alfha Abrianto L. Tobing ◽  
I Ketut Sukarasa ◽  
Mahmud Yusuf
Keyword(s):  
Gravity Anomaly ◽  
Bouguer Anomaly ◽  
Secondary Data ◽  
Coefficient Of Determination ◽  
Satellite Gravity ◽  
Mapping Tool ◽  
Anomaly Map ◽  
Bouguer Anomaly Map ◽  
Gravity Interpretation ◽  
Earthquake Data

This study aims to determine the value of the gravity anomaly in the Bali region, identify the fault structure in the Bali region using gravity interpretation and analyze the relationship between gravity anomaly and seismicity in the Bali region. The data used is secondary data, namely satellite gravity anomaly data obtained from the topex website and earthquake data obtained from the Indonesian Agency for Meteorological, Climatological, and Geophysics (BMKG) catalog. Data processing in this study was done using gravity and Second Vertical Derivative (SVD) methods. We used Surfer15 software, Oasis Montaj, and the Generic Mapping Tool (GMT). The results of the complete Bouguer anomaly map show the anomalous value of the study area between 10-220 mGal, regional anomaly 40-190 mGal, and the residual anomaly between (-120)-60 mGal. Judging from the SVD contour map that has included earthquake data in the Bali region for the 2008-2020 period, the type of fault in the Seririt Fault, Tejakula Fault, and Fault around Mount Agung is a thrust fault. Judging from the value of the coefficient of determination, it shows that 99% of the seismicity value is influenced by gravity anomaly. The higher the value of the gravity anomaly, the higher the seismicity value.

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