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.

THE USE OF POISSON’S RELATION FOR THE EXTRACTION OF PSEUDOTOTAL MAGNETIC FIELD INTENSITY FROM GRAVITY OBSERVATIONS

Geophysics ◽  
1971 ◽  
Vol 36 (3) ◽  
pp. 605-608 ◽  
Author(s):  
Edwin S. Robinson
Keyword(s):  
Magnetic Field ◽  
Gravity Field ◽  
Field Data ◽  
Field Potential ◽  
Geological Structure ◽  
Common Source ◽  
Uniform Density ◽  
Practical Applications ◽  
Uniform Magnetization ◽  
Gravity Fields

Investigation of geological structure by gravimetric and magnetic field surveys requires consideration of relationships between gravity anomaly and magnetic anomaly generating sources. The possibility of using Poisson’s Relation to examine magnetic and gravity fields related to a common source is intriguing. This relation is expressed as follows: [Formula: see text] (1) where A (x, y, z) is the magnetic field potential and U (x, y, z) is the gravity field potential at a point in space due to a source of uniform density ρ and uniform magnetization I in the direction α. This expression has been used to derive magnetic anomalies over idealized forms (Nettleton, 1940) and, by Baranov (1957), to extract pseudogravity fields from magnetic field data. The purpose of this paper is to develop an expression for extracting a pseudomagnetic field from gravity field data and to examine the practical applications of this expression.

X.—A Gravity Survey in Ayrshire and its Geological Interpretation

1966 ◽  
Vol 66 (10) ◽  
pp. 239-265 ◽  
Author(s):  
Adam C. McLean
Keyword(s):  
Gravity Field ◽  
Bouguer Anomaly ◽  
Gravity Survey ◽  
Normal Faults ◽  
Red Sandstone ◽  
Geological Interpretation ◽  
The North ◽  
Close Relationship ◽  
Lower Palaeozoic ◽  
Western Limb

SynopsisBouguer anomaly maps covering most of Ayrshire at a density of about one station per sq. km., show a close relationship between anomalies and the distribution of the Upper Palæozoic rocks in the area south of the Inch-gotrick Fault, but are less clearly interpreted to the north, where thick dense igneous masses are present.In central and south Ayrshire the gravity field may be largely interpreted in terms of the known density-contrasts at the interfaces separating Upper and Lower Old Red Sandstone, and Lower Old Red Sandstone and Lower Palæozoic rocks. The major structure, the Mauchline Basin, is reflected clearly in the largest anomaly, and there is evidence of a culmination of its south-western limb near Kirkoswald. The important N.E.–S.W. faults also give rise to large anomalies, which may be connected with the known geology. It is inferred that they moved as normal faults in Carboniferous times, and that the adjacent synclines are essentially sags associated with the fault displacements. There is geophysical evidence that both the Southern Upland and Kerse Loch Faults existed in Middle O.R.S. (proto-Armorican) times. It is concluded that a hypothesis of N.–S. Armorican stress is not valid in south Ayrshire.In north Ayrshire, many of the anomalies are best explained by changes of thickness of the Millstone Grit lavas and of the Clyde Plateau lavas, and by the presence of thick dolerite intrusions. Additional evidence is needed, however, before final conclusions may be drawn.

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.

Discussion by Leo J. Peters and Thomas A. Elkins

Geophysics ◽  
1953 ◽  
Vol 18 (4) ◽  
pp. 907-909 ◽  
Author(s):  
L. J. Peters ◽  
T. A. Elkins
Keyword(s):  
Gravity Field ◽  
Field Data ◽  
Gravity Data ◽  
Practical Importance ◽  
Gravity Survey ◽  
Second Derivative ◽  
Geologic Structure ◽  
The Real ◽  
Real Effects

We would like to call attention to a point of considerable practical importance which is neglected in this interesting and ingenious paper on the computation of the second derivative. This is the fact that gravity field data inevitably contain errors so that the second derivative values computed by coefficients from this gravity data also will contain errors, which may be of such magnitude as to mask the real effects caused by geologic structure, the finding of which was the purpose of the gravity survey.

Analysis of Underground Space Azimuth Measuring and Data Processing in a Tunnel

2014 ◽  
Vol 580-583 ◽  
pp. 2828-2832
Author(s):  
Tao Wang ◽  
Hu Rong Duan ◽  
Liu Tao Jiang ◽  
Shun Liu
Keyword(s):  
Measurement Error ◽  
Data Processing ◽  
Measurement Accuracy ◽  
High Accuracy ◽  
Measurement Precision ◽  
Underground Space ◽  
Processing Theory ◽  
Constant Measurement ◽  
Survey Results ◽  
Final Orientation

In this paper, we studied high accuracy azimuth measuring on improving the precision of traverse azimuth from the perspective of transfixion measurement error in a tunnel project. On the basis of a feasible scheme using Gyro Total Station measurement is given. Data processing theory and method are also introduced with a successful tunnel transfixion case. The transfixion results show that the instrument constant measurement precision is 3.7", baseline coordinates azimuth measurement accuracy is 4.8" into tunnel, the final orientation coordinate azimuth value and traverse measurement values differ is 11", to guide the construction of the gyro orientation with survey results achieved tunnel through smoothly.

scholarly journals Shaping the Evolution of CME towards better Outcomes: Proceedings of the 2018 ISSECAM Colloquium

2019 ◽  
Author(s):  
Martin C. Michel ◽  
Jaan Toelen ◽  
Bertrand Tombal ◽  
Vassilios Papalois ◽  
Peter Littlejohns ◽  
...  
Keyword(s):  
Medical Education ◽  
Patient Outcomes ◽  
Health Care Professionals ◽  
Real Life ◽  
Medical Practitioners ◽  
Effective Learning ◽  
Life Long Learning ◽  
Learning Practices ◽  
Appropriate Care ◽  
Survey Results

Abstract Continuing medical education (CME) as part of life-long learning in medicine should focus on patient outcomes and appropriate care by increasing knowledge, competence and/or performance of clinicians. In this article, we present the views of the different stakeholders on the future of CME, presented at the ISSECAM colloquium held in December 2018. Within the framework of the colloquium, a survey was done asking health care professionals about their learning practices. We present an integrated summary of the attendees’ views and survey results. Key elements for effective learning in CME and how they can be implemented have been identified. Increased interactivity and focus on real-life practice seem to have the highest likelihood to induce behavioural changes. In addition, online CME activities will steadily gain more weight in the learning curriculum of medical practitioners. CME providers should take these elements (interactivity, real-life practice, online) into consideration when designing their different activities.

scholarly journals Overview of Geothermal Potential in Momiwaren, South Manokwari Regency using Earth Gravity Field Analysis

2021 ◽  
Vol 3 (2) ◽  
pp. 97-109
Author(s):  
Richard Lewerissa
Keyword(s):  
Gravity Field ◽  
Bouguer Anomaly ◽  
Gravity Anomalies ◽  
Geological Structure ◽  
Field Analysis ◽  
Terrain Model ◽  
Earth Gravity ◽  
Qualitative Interpretation ◽  
Rock Formations ◽  
Global Gravity

West Papua province has a geothermal resource that can be established as renewable electricity energy or tourism. One of the locations for geothermal prospects is in the Momiwaren district of South Manokwari regency. A preliminary study in form of a qualitative interpretation has been conducted through the analysis of high-resolution of earth gravity fields from the Global Gravity Map developed by Curtin University, Australia. This research was performed to increase the boundary of the geological structure which indicates the existence of a source of manifestation of hotsprings and the fault structures that control it. The study begins with the reduction of the gravity field data to obtain a complete Bouguer anomaly based on the SRTM2gravity terrain model correction. Furthermore, regional and residual gravity anomalies are separated, and vertical and horizontal gravitational gradient analysis using 2-D fast Fourier transform. Qualitative interpretation produces models and boundaries of the main structure and the corresponding Demini and Gaya Baru faults and the distribution of the geological rock formations in the study area. This interpretation provides useful information as a constraint for quantitative interpretation through subsurface inversion modeling to obtain detailed geothermal models in Momiwaren.

scholarly journals ANALYSIS OF ISOSTATICALLY-BALANCED CORTICAL MODELS USING MODERN GLOBAL GEOPOTENTIAL MODELS

2017 ◽  
Vol 23 (4) ◽  
pp. 623-635
Author(s):  
Claudia Infante ◽  
Claudia Tocho ◽  
Daniel Del Cogliano
Keyword(s):  
Gravity Field ◽  
Temporal Variations ◽  
Geoid Height ◽  
Geological Structure ◽  
Earth’S Gravity Field ◽  
Isostatic Equilibrium ◽  
Geopotential Models ◽  
Show Evidence ◽  
Residual Geoid ◽  
Cortical Models

Abstract: The knowledge of the Earth's gravity field and its temporal variations is the main goal of the dedicated gravity field missions CHAMP, GRACE and GOCE. Since then, several global geopotential models (GGMs) have been released. This paper uses geoid heights derived from global geopotential models to analyze the cortical features of the Tandilia structure which is assumed to be in isostatic equilibrium. The geoid heights are suitably filtered so that the structure becomes apparent as a residual geoid height. Assuming that the geological structure is in isostatic equilibrium, the residual geoid height can be assimilated and compared to the isostatic geoid height generated from an isostatically compensated crust. The residual geoid height was obtained from the EGM2008 and the EIGEN-6C4 global geopotential models, respectively. The isostatic geoid was computed using the cortical parameters from the global crustal models GEMMA and CRUST 1.0 and from local parameters determined in the area under study. The obtained results make it clear that the isostatic geoid height might become appropriate to validate crustal models if the structures analyzed show evidence of being in isostatic equilibrium.

scholarly journals SOUTH NATUNA BASIN RECONFIGURATION BASED ON RECENT SEISMIC AND GRAVITY SURVEYS

2019 ◽  
Vol 42 (2) ◽  
pp. 65-71
Author(s):  
Tatang Padmawidjaja ◽  
Yusuf Iskandar ◽  
Andy Setyo Wibowo ◽  
Eko Budi Lelono
Keyword(s):  
Seismic Data ◽  
Gravity Data ◽  
Sedimentary Rocks ◽  
Geological Structure ◽  
Seismic Survey ◽  
Seismic Region ◽  
Seismic Line ◽  
Geological Information ◽  
Survey Results ◽  
Basin Area

The Geological Survey Center has conducted a seismic survey in the southern Natuna Sea region to obtain geological information below relating to the potential energy resources of the area. The area research is located in the western part and outside the Singkawang Basin area (BG, 2008), which is separated by a Metamorf ridge. 2D seismic survey results show 3 different rock units, namely shallow marine sedimentary rocks, tertiary sedimentary rocks and pre-Tertiary sedimentary rocks, with pre-Tertiary sediment depths of less than 2000 ms. Interpretation of seismic data shows the pattern of graben structures that form sub-basins. strong refl ectors seen in seismic record can distinguish pre-rift, syn-rift and post-rift deposits. There are 2 wells, namely Datuk 1X and Ambu 1X. Datuk 1X has a depth of 1187 meters, and The Ambu 1X has a depth of 880 meters that is crossed by a seismic line. Both drilling has obtained Tertiary aged sandstone that covers pre-Tertiary bedrock.Gravity anomaly data in the seismic region shows anomaly values between 10 to 54 mgal which form the anomaly ridge and basinThe ridge anomaly extends as an anticline, while the anomaly basin also rises to form a syncline. Sincline and anticline trending southwest - southeast, with widening and narrowing patterns.Based on its geological model, the depth of the sediment is relatively shallow between 1500 to 2000 meters. While the integration between seismic, gravity and geomagnetic data shows the discovery of new basins that have never been described before.Finally, the integration of seismic and gravity data succeed discovers a new basin which has never been delineated before. In addition, it shows the continuity of the regional geological structure spanning from the studied area to the West Natuna Basin which is well known to be rich in hydrocarbon potential.

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