Improvement of the conic prism model for terrain correction in rugged topography

Geophysics ◽  
1981 ◽  
Vol 46 (7) ◽  
pp. 1054-1056 ◽  
Author(s):  
Raymond J. Olivier ◽  
Réjean G. Simard
Keyword(s):  
Gravity Anomalies ◽  
Terrain Correction ◽  
Field Calculation ◽  
Bouguer Gravity ◽  
New Model ◽  
Gravity Station ◽  
Rugged Terrain ◽  
Rugged Topography ◽  
Terrain Corrections ◽  
Prism Model

Terrain corrections for Bouguer gravity anomalies are generally obtained from topographic models represented by flat‐topped compartments of circular zones, utilizing the so‐called Hayford‐Bowie (1912), or Hammer’s (1939) method. Some authors have introduced improved relief models for taking uniform slope into consideration (Sandberg, 1958; Kane, 1962; Takin and Talwani, 1966; Campbell, 1980). We present a new model that increases the accuracy of the calculation of terrain correction close to the gravity station in rugged terrain, especially when conventional templates with few zones are used in field calculation.

scholarly journals Gravity terrain correction for mainland territory of Vietnam

2017 ◽  
Vol 17 (4B) ◽  
pp. 145-150
Author(s):  
Pham Nam Hung ◽  
Cao Dinh Trieu ◽  
Le Van Dung ◽  
Phan Thanh Quang ◽  
Nguyen Dac Cuong
Keyword(s):  
Gravity Data ◽  
Computing Time ◽  
Terrain Correction ◽  
Bouguer Gravity ◽  
Mountainous Region ◽  
Terrain Effect ◽  
Rugged Topography ◽  
Terrain Corrections ◽  
Gravity Map

Terrain corrections for gravity data are a critical concern in rugged topography, because the magnitude of the corrections may be largely relative to the anomalies of interest. That is also important to determine the inner and outer radii beyond which the terrain effect can be neglected. Classical methods such as Lucaptrenco, Beriozkin and Prisivanco are indeed too slow with radius correction and are not extended while methods based on the Nagy’s and Kane’s are usually too approximate for the required accuracy. In order to achieve 0.1 mGal accuracy in terrain correction for mainland territory of Vietnam and reduce the computing time, the best inner and outer radii for terrain correction computation are 2 km and 70 km respectively. The results show that in nearly a half of the Vietnam territory, the terrain correction values ≥ 10 mGal, the corrections are smaller in the plain areas (less than 2 mGal) and higher in the mountainous region, in particular the correction reaches approximately 21 mGal in some locations of northern mountainous region. The complete Bouguer gravity map of mainland territory of Vietnam is reproduced based on the full terrain correction introduced in this paper.

TERRAIN CORRECTIONS FOR GRAVIMETER STATIONS

Geophysics ◽  
1939 ◽  
Vol 4 (3) ◽  
pp. 184-194 ◽  
Author(s):  
Sigmund Hammer
Keyword(s):  
Gravitational Effect ◽  
Relative Accuracy ◽  
Terrain Correction ◽  
Gravitational Attraction ◽  
Gravity Station ◽  
Terrain Corrections ◽  
Instrumental Precision

In this paper the correction for the gravitational attraction of the topography on a gravity station is considered as consisting of two parts; (1) the restricted but conventional “Bouguer correction” which postulates as a convenient approximation that the topography consists of an infinite horizontal plain, and (2) the “Terrain correction” which is a supplementary correction taking into account the gravitational effect of the undulations of the terrain about the plane through the gravity station. The paper illustrates the necessity of making terrain corrections if precise gravity surveys are desired in hilly country and presents terrain correction tables with which this quantity may be determined to a relative accuracy of one‐tenth milligal. This accuracy is required to fully utilize the high instrumental precision of modern gravimeters.

Gravity terrain corrections for stations on a uniform slope—A power law approximation

Geophysics ◽  
1980 ◽  
Vol 45 (1) ◽  
pp. 109-112 ◽  
Author(s):  
David L. Campbell
Keyword(s):  
Power Law ◽  
Terrain Correction ◽  
Gravity Station ◽  
Rule Of Thumb ◽  
Terrain Corrections ◽  
Special Case ◽  
Hand Calculator

A hand calculator program for gravity terrain corrections should include functions to (1) calculate the standard terrain correction due to topography of constant elevation throughout a given sector of a terrain correction graticule, and (2) calculate the terrain correction due to topography that slopes uniformly throughout the graticule sector. Equations for function (1) and for a special case of function (2) were given by Hammer (1939). Hammer’s equation covers the useful case where the uniform slope extends in azimuth a full 360 degrees around the gravity station. Using this equation, Sandburg (1958) published tables of gravity terrain corrections for stations on complete (360 degree) uniform slopes of slope angles 0 degrees to 30 degrees. This note points out that Hammer’s equation, as well as the corresponding equation for the incomplete uniform slope (one extending under a single graticule sector only), may both be approximated by a square‐power law. The resulting forms are particularly convenient for hand calculator use. A particular application gives a new rule of thumb for estimating Hammer inner‐zone terrain corrections.

A sloping wedge technique for calculating gravity terrain corrections

Geophysics ◽  
1991 ◽  
Vol 56 (7) ◽  
pp. 1061-1063 ◽  
Author(s):  
L. J. Barrows ◽  
J. D. Fett
Keyword(s):  
High Precision ◽  
Field Data ◽  
Open Space ◽  
Gravity Station ◽  
Topographic Features ◽  
Original Field ◽  
Rugged Topography ◽  
Terrain Corrections ◽  
Wedge Technique

Gravity terrain corrections account for the upward pull of topographic features which are higher than a gravity station (hills) and the lack of downward pull from open space which is lower than the station (valleys). In areas of rugged topography or in high precision surveys, the magnitude of the terrain corrections can be comparable to the anomalies being sought and the uncertainties in the terrain corrections can limit the accuracy of the survey. Also, calculating the corrections can require more time and effort than gathering the original field data. Even if terrain corrections are not made, it is necessary to show that their omission does not compromise the integrity of the survey.

GRAVITY TERRAIN CORRECTIONS USING MULTIQUADRIC EQUATIONS

Geophysics ◽  
1976 ◽  
Vol 41 (2) ◽  
pp. 266-275 ◽  
Author(s):  
Douglas H. Krohn
Keyword(s):  
Linear System ◽  
Numerical Integration ◽  
Digital Computer ◽  
Digital Terrain Model ◽  
Computer Method ◽  
Gravity Station ◽  
Terrain Model ◽  
Digital Terrain ◽  
Rugged Topography ◽  
Terrain Corrections

A digital computer method of making gravity station terrain corrections has been developed that uses a linear system of multiquadric equations. This system is fitted to the points defined by square topographic compartments and the point defined by the station itself to give a mathematically described surface. The surface is a better model of the actual topography than the digital terrain model, especially near the station. Terrain correction of this surface is calculated using a simple and fast numerical integration. A theoretical example shows that the multiquadric equation method is potentially more accurate than a hand chart method for near‐station terrain corrections. Field examples in an area of rugged topography show that the method can be successfully used for actual gravity stations.

A new sedimentary cover model for the southern area of the East European Platform and the Pre-Caucasus based on decompensation gravity anomalies data

2021 ◽  
Author(s):  
Mikhail Kaban ◽  
Alexei Gvishiani ◽  
Roman Sidorov ◽  
Alexei Oshchenko ◽  
Roman Krasnoperov
Keyword(s):  
East European Platform ◽  
Sedimentary Cover ◽  
Gravity Anomalies ◽  
Sedimentary Basins ◽  
The Caucasus ◽  
Near Surface ◽  
New Model ◽  
Origin And Evolution ◽  
East European ◽  
Bouguer Anomalies

<p><span>A new model has been developed for the density and thickness of the sedimentary cover in a vast region at the junction of the southern part of the East European Platform, the Pre-Caucasus and some structures adjacent to the south, including the Caucasus. Structure and density of sedimentary basins was studied by employing the approach based on decompensation of gravity anomalies. Decompensative correction for gravity anomalies reduces the effect of deep masses providing compensation of near-surface density anomalies, in contrast to the conventional isostatic or Bouguer anomalies. . The new model of sediments, which implies their thickness and density, gives a more detailed description of the sedimentary thickness and density and reveals new features which were not or differently imaged by previous studies. It helps in better understanding of the origin and evolution of the basins and provides a background for further detailed geological and geophysical studies of the region.</span></p>

Modeling of the Bouguer Gravity Anomalies for Mineral Prospection

2021 ◽  
Author(s):  
J.S. Kayode ◽  
M.H. Arifin ◽  
A. Omar ◽  
N. Sulaiman ◽  
A. Dzulkifli ◽  
...  
Keyword(s):  
Gravity Anomalies ◽  
Bouguer Gravity ◽  
Bouguer Gravity Anomalies

scholarly journals Necessity of Terrain Correction in Magnetotelluric Data Recorded from Garhwal Himalayan Region, India

Geosciences ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 482
Author(s):  
Dharmendra Kumar ◽  
Arun Singh ◽  
Mohammad Israil
Keyword(s):  
Real Data ◽  
Terrain Correction ◽  
Himalayan Region ◽  
General Character ◽  
Period Range ◽  
Magnetotelluric Data ◽  
Heterogeneous Models ◽  
Corrected Data ◽  
Terrain Corrections ◽  
And Inversion

The magnetotelluric (MT) method is one of the useful geophysical techniques to investigate deep crustal structures. However, in hilly terrains, e.g., the Garhwal Himalayan region, due to the highly undulating topography, MT responses are distorted. Such responses, if not corrected, may lead to the incorrect interpretation of geoelectric structures. In the present paper, we implemented terrain corrections in MT data recorded from the Garhwal Himalayan Corridor (GHC). We used AP3DMT, a 3D MT data modeling and inversion code written in the MATLAB environment. Terrain corrections in the MT impedance responses for 39 sites along the Roorkee–Gangotri profile in the period range of 0.01 s to 1000 s were first estimated using a synthetic model by recording the topography and locations of MT sites. Based on this study, we established the general character of the terrain and established where terrain corrections were necessary. The distortion introduced by topography was computed for each site using homogenous and heterogeneous models with actual topographic variations. Period-dependent, galvanic and inductive distortions were observed at different sites. We further applied terrain corrections to the real data recorded from the GHC. The corrected data were inverted, and the inverted model was compared with the corresponding inverted model obtained with uncorrected data. The modification in electrical resistivity features in the model obtained from the terrain-corrected response suggests the necessity of terrain correction in MT data recorded from the Himalayan region.

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