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.

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.

THE APPLICATION OF GRAVITY INTERPRETATION TO AN INTRA CRATONIC BASIN

1978 ◽  
Vol 18 (1) ◽  
pp. 130
Author(s):  
C. N. G. Dampney ◽  
B. D. Johnson ◽  
R. J. S. Hollingsworth
Keyword(s):  
Gravity Field ◽  
Measurement Accuracy ◽  
Geological Structure ◽  
Gravity Survey ◽  
Appropriate Care ◽  
Other Information ◽  
Survey Results ◽  
Gravity Interpretation ◽  
Shallow Structure ◽  
Cooper Basin

I he Cooper Basin is a good example of a tectonically complex area, and this complexity is reflected in the gravity field. The gravity field caused by the sediments is distorted by the influence of a relatively strong regional field. Nevertheless along profiles over which gravity has been measured with appropriate care, the various components of the gravity field can be analysed and separated.In the Cooper Basin the form of the regional field has been determined. As a result the structure of a major pre-Permian unconformity, which defines the base of the sediments mainly causing the gravity field anomaly, can be contoured. Other information related to some shallow structure is also derived.The pertinent point emphasized by the Cooper Basin example is that over similarly complex areas gravity survey results can only be effectively used once the various components of the field are properly analysed. Scattered regional measurements may be of some value where the regional field varies little. In general, however, a few detailed profiles must also be available to upgrade gravity interpretation to the level where it is of immediate value in the early stages of oil exploration.Specifications are therefore presented which detail gravity, elevation and positioning measurement accuracy as well as survey procedures necessary to detect geological structure at given depths.

Interactive gravity inversion

Geophysics ◽  
2006 ◽  
Vol 71 (1) ◽  
pp. J1-J9 ◽  
Author(s):  
João B. C. Silva ◽  
Valéria C. F. Barbosa
Keyword(s):  
Gravity Field ◽  
Field Data ◽  
Synthetic Data ◽  
The Other ◽  
Density Contrast ◽  
Gravity Inversion ◽  
Homogeneous Body ◽  
New Approach ◽  
Line Segments ◽  
Gravity Fields

We have developed a new approach for estimating the location and geometry of several density anomalies that give rise to a complex, interfering gravity field. The user interactively defines the assumed outline of the true gravity sources in terms of points and line segments, and the method estimates sources closest to the specified outline to achieve a match between the predicted and observed gravity fields. Each gravity source is assumed to be a homogeneous body with a known density contrast; different density contrasts may be assigned to each source. Tests with synthetic data show that the method can be of use in estimating (1) multiple laterally adjacent and closely situated gravity sources, (2) single gravity sources consisting of several homogeneous compartments with different density contrasts, and (3) two gravity sources with different density contrasts of the same sign, one totally enclosed by the other. The method is also applied to three different sets of field data where the gravity sources belong to the same categories established in the tests with synthetic data. The method produces solutions consistent with the known geologic attributes of the gravity sources, illustrating its potential practicality.

scholarly journals Seafloor Density Contrast Derived From Gravity and Shipborne Depth Observations: A Case Study in a Local Area of Atlantic Ocean

2021 ◽  
Vol 9 ◽  
Author(s):  
Xiaoyun Wan ◽  
Weipeng Han ◽  
Jiangjun Ran ◽  
Wenjie Ma ◽  
Richard Fiifi Annan ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Local Area ◽  
Density Variation ◽  
Mean Difference ◽  
Density Contrast ◽  
Data Sets ◽  
Marine Gravity ◽  
Band Pass

Marine gravity data from altimetry satellites are often used to derive bathymetry; however, the seafloor density contrast must be known. Therefore, if the ocean water depths are known, the density contrast can be derived. This study experimented the total least squares algorithm to derive seafloor density contrast using satellite derived gravity and shipborne depth observations. Numerical tests are conducted in a local area of the Atlantic Ocean, i.e., 34°∼32°W, 3.5°∼4.5°N, and the derived results are compared with CRUST1.0 values. The results show that large differences exist if the gravity and shipborne depth data are used directly, with mean difference exceeding 0.4 g/cm3. However, with a band-pass filtering applied to the gravity and shipborne depths to ensure a high correlation between the two data sets, the differences between the derived results and those of CRUST1.0 are reduced largely and the mean difference is smaller than 0.12 g/cm3. Since the spatial resolution of CRUST1.0 is not high and in many ocean areas the shipborne depths and gravity anomalies are much denser, the method of this study can be an alternative method for providing seafloor density variation information.

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.

scholarly journals The use of «native» wavelet transform for determining lateral density variation of the Volgo-Uralian subcraton

2021 ◽  
pp. 135-140
Author(s):  
I. N. Ognev ◽  
◽  
E. V. Utemov ◽  
D. K. Nurgaliev ◽  
◽  
...  
Keyword(s):  
Wavelet Transform ◽  
Gravity Field ◽  
Regional Scale ◽  
Density Variation ◽  
Gravity Modeling ◽  
Regional Models ◽  
Residual Gravity ◽  
Satellite Gravimetry ◽  
Scale Models ◽  
Residual Gravity Anomaly

In the last two decades in conjunction with the development of satellite gravimetry, the techniques of regional-scale inverse and forward gravity modeling started to be more actively incorporated in the construction of crustal and lithospheric scale models. Such regional models are usually built as a set of layers and bodies with constant densities. This approach often leads to a certain difference between the initially used measured gravity field and a gravity field that is produced by the model. One of the examples of this kind of models is a recent lithospheric model of the Volgo-Uralian subcraton. In the current study, we are applying the method of «native» wavelet transform to the residual gravity anomaly for defining the possible lateral density variations within the lithospheric layers of Volgo-Uralia. Keywords: wavelet transform; gravity field inversion; forward gravity modeling; Volgo-Uralian subcraton; satellite gravimetry.

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