DETERMINATION AND MAPPING OF THE TERRESTRIAL GRAVITY ANOMALIES IN THE MOUNTAINOUS AREAS OF IRAQ

Gravity data and computing gravity anomalies are regarded as vital for both geophysics and physical geodesy fields. The mountainous areas of Iraq are characterized by the lack of regional gravity data because gravity surveys are rarely performed in the past four decades due to the Iraq-Iran war and the internal unstable political situation of this particular region. In addition, the formal map of the available terrestrial gravity which was published by the French Database of Bureau Gravimetrique International (International Gravimetric Bureau-in English) (BGI), introduces Iraq and the study area as a remote area and in white color because of the unavailability of gravity data. However, a dense and local (not regional) gravity data is available which was conducted by geophysics researchers 13 years ago. Therefore, the regional gravity survey of 160 gravity points was performed by the authors at an average 11 km apart, which was covers the whole area of Sulaymaniyah Governorate (part of the mountainous areas of Iraq). In spite of Although the risk of mine fields within the study area, suitable safe routes as well as a helicopter was used for the gravity survey of several points on the top of mountains. The survey was conducted via Lacoste and Romberg geodetic gravimeter and GPS handheld. The objective of the study is to determine and map the gravity anomalies for the entire study area, the data of which would assist different geosciences applications.

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Towards an updated, enhanced regional gravity field solution for Antarctica

10.5194/egusphere-egu21-9873 ◽

2021 ◽

Author(s):

Mirko Scheinert ◽

Philipp Zingerle ◽

Theresa Schaller ◽

Roland Pail ◽

Martin Willberg

Keyword(s):

Gravity Anomaly ◽

Gravity Field ◽

Gravity Data ◽

Gravity Anomalies ◽

Data Set ◽

Gravity Field Model ◽

Terrestrial Gravity ◽

Field Solution ◽

Gravity Disturbances ◽

Regional Gravity

In the frame of the IAG Subcommission 2.4f &#8220;Gravity and Geoid in Antarctica&#8221; (AntGG) a first Antarctic-wide grid of ground-based gravity anomalies was released in 2016 (Scheinert et al. 2016). That data set was provided with a grid space of 10 km and covered about 73% of the Antarctic continent. Since then a considerably amount of new data has been made available, mainly collected by means of airborne gravimetry. Regions which were formerly void of any terrestrial gravity observations and have now been surveyed include especially the polar data gap originating from GOCE satellite gravimetry. Thus, it is timely to come up with an updated and enhanced regional gravity field solution for Antarctica. For this, we aim to improve further aspects in comparison to the AntGG 2016 solution: The grid spacing will be enhanced to 5 km. Instead of providing gravity anomalies only for parts of Antarctica, now the entire continent should be covered. In addition to the gravity anomaly also a regional geoid solution should be provided along with further desirable functionals (e.g. gravity anomaly vs. disturbance, different height levels).We will discuss the expanded AntGG data base which now includes terrestrial gravity data from Antarctic surveys conducted over the past 40 years. The methodology applied in the analysis is based on the remove-compute-restore technique. Here we utilize the newly developed combined spherical-harmonic gravity field model SATOP1 (Zingerle et al. 2019) which is based on the global satellite-only model GOCO05s and the high-resolution topographic model EARTH2014. We will demonstrate the feasibility to adequately reduce the original gravity data and, thus, to also cross-validate and evaluate the accuracy of the data especially where different data set overlap. For the compute step the recently developed partition-enhanced least-squares collocation (PE-LSC) has been used (Zingerle et al. 2021, in review; cf. the contribution of Zingerle et al. in the same session). This method allows to treat all data available in Antarctica in one single computation step in an efficient and fast way. Thus, it becomes feasible to iterate the computations within short time once any input data or parameters are changed, and to easily predict the desirable functionals also in regions void of terrestrial measurements as well as at any height level (e.g. gravity anomalies at the surface or gravity disturbances at constant height).We will discuss the results and give an outlook on the data products which shall be finally provided to present the new regional gravity field solution for Antarctica. Furthermore, implications for further applications will be discussed e.g. with respect to geophysical modelling of the Earth&#8217;s interior (cf. the contribution of Schaller et al. in session G4.3).

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Empirical Determination of the Gravity Anomaly Covariance Function in Mountainous Areas

The Canadian Surveyor ◽

10.1139/tcs-1980-0035 ◽

1980 ◽

Vol 34 (3) ◽

pp. 251-264 ◽

Cited By ~ 3

Author(s):

Gerard Lachapelle ◽

K. P. Schwarz

Keyword(s):

Gravity Anomaly ◽

Covariance Function ◽

Physical Geodesy ◽

Gravity Anomalies ◽

Mountainous Areas ◽

The North ◽

Regression Parameters ◽

Free Air ◽

Vening Meinesz ◽

Free Air Gravity

An evaluation of the empirical gravity anomaly covariance function using over 95 000 surface gravity anomalies in the North American Western Cordillera was carried out. A regression analysis of the data exhibits a strong and quasi-linear correlation of free air gravity anomalies with heights. This height correlation is removed from the free air anomalies prior to the numerical evaluation of the gravity anomaly covariance function. This covariance function agrees well with that evaluated previously by the authors for the remainder of Canada. A possible use for such a covariance function of ‘height independent’ gravity anomalies in mountainous areas is described. First, the height independent gravity anomaly at a point of known height is evaluated by least squares prediction using neighboring measured height independent gravity anomalies. Secondly, the part caused by the height correlation is calculated using linear regression parameters estimated previously and added to the predicted height independent gravity anomaly to obtain a predicted standard free air anomaly. This technique can be used to densify the coverage of free air anomalies for subsequent use in integral formulas of physical geodesy, e.g., those of Stokes and Vening Meinesz. This method requires that point topographic heights be given on a grid.

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REGIONAL GRAVITY SURVEY IN NORTHEASTERN OKLAHOMA AND SOUTHEASTERN KANSAS

Geophysics ◽

10.1190/1.1438221 ◽

1956 ◽

Vol 21 (1) ◽

pp. 88-106 ◽

Cited By ~ 1

Author(s):

Kenneth L. Cook

Keyword(s):

Structural Geology ◽

Bouguer Anomaly ◽

Gravity Anomalies ◽

Close Correlation ◽

Geodetic Survey ◽

Gravity Survey ◽

Complex Nature ◽

Gravity Gradients ◽

Anomaly Map ◽

Regional Gravity

In 1948 the U. S. Geological Survey, in cooperation with the U. S. Coast and Geodetic Survey, made a regional gravity survey in northeastern Oklahoma and southeastern Kansas in connection with the studies of the deflection of the vertical. About 550 gravity stations were occupied with spacings of 5 to 10 miles in parts of 54 counties, and a Bouguer anomaly map, contoured at intervals of 5 milligals, was drawn. In southeastern Kansas there is a lack of correlation of regional gravity with known regional structural geology. The observed gravity anomalies are apparently caused principally by variations of density in the Precambrian basement and indicate a basement of complex nature, made up of rocks of contrasting properties, with a regional grain striking predominantly west or west‐northwest. In northeastern Oklahoma the several observed regional gravity anomalies indicate different degrees of correlation of regional gravity with regional structural geology. In the Precambrian highland area in Osage, Pawnee, and Creek Counties, there is a lack of correlation, as the gravity anomaly is probably caused chiefly by density contrasts within the basement complex. The anomaly associated with the Hunton arch is probably caused partly by structural relief of the rocks of pre‐Pennsylvanian age and partly by density contrasts within the basement, and thus indicates some correlation. The steep gravity gradients along the outer flanks of the Ozark uplift indicate good correlation with the subsurface geology. The great anomaly over the Arkansas basin, which indicates a close correlation, is probably caused largely—but perhaps not entirely—by downwarping of the basement and pre‐Pennsylvanian rocks.

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Penerapan Persamaan Trend Surface Analysis untuk Pemisahan Anomali Residual dan Regional pada Data Gayaberat

JURNAL GEOCELEBES ◽

10.20956/geocelebes.v5i2.14023 ◽

2021 ◽

pp. 102-115

Author(s):

Purwaditya Nugraha ◽

Nono Agus Santoso

Keyword(s):

Surface Analysis ◽

Gravity Data ◽

Synthetic Data ◽

Gravity Anomalies ◽

Analysis Method ◽

Trend Surface Analysis ◽

Microsoft Excel ◽

Trend Surface ◽

Surface Analysis Method ◽

Regional Gravity

The separation of regional anomalies and residual anomalies in gravity data is an important part in interpreting gravity data. This process aims to obtain gravity anomalies that have been associated with exploration targets. The Trend Surface Analysis method is a mathematical approach to the earth field that can be used to separate maps into regional components and local components. The application of this method into gravity data can be used to separate regional anomalies and residual anomalies. The process of processing the trend surface analysis method can be done using Microsoft Excel. This method is tested first on synthetic gravity data, the purpose of this test is to determine the performance of the trend surface analysis method in performing anomaly separation. Based on the test results of the trend surface analysis method on synthetic gravity data, it was found that this method was quite good at separating regional anomalies and residual anomalies. This is evidenced by the anomalous pattern that is already the same between the regional gravity anomaly resulting from the separation of the anomaly using the trend surface analysis method and the regional anomaly resulting from synthetic data. The same anomaly pattern can also be seen in the residual anomaly resulting from the separation of the anomaly using the trend surface analysis method with the residual anomaly resulting from synthetic data. The application of the trend surface analysis method to field data has been carried out by producing regional anomalies and residual anomalies. This method is very good at separating regional anomalies and residual anomalies, especially in regional anomalies located at deep depths.Pemisahan anomali regional dan anomali residual pada data gayaberat merupakan bagian penting dalam melakukan interpretasi data gayaberat. Proses ini bertujuan untuk mendapatkan anomali gayaberat yang sudah berasosiasi dengan target eksplorasi. Metode Trend Surface Analysis merupakan teknik pendekatan matematika pada bidang kebumian yang dapat digunakan untuk memisahkan peta kedalam komponen regional dan komponen lokal. Penerapan metode ini ke dalam data gayaberat dapat digunakan untuk memisahkan anomali regional dan anomali residual. Proses pengolahan metode trend surface analysis dapat dilakukan dengan menggunakan microsoft excel. Metode ini diuji terlebih dahulu pada data gayaberat sintetis, tujuan pengujian ini adalah untuk mengetahui performa metode trend surface analysis dalam melakukan pemisahan anomali. Berdasarkan hasil pengujian metode trend surface analysis pada data gayaberat sintetis didapatkan bahwa metode ini cukup baik dalam memisahkan anomali regional dan anomali residual. Hal ini dibuktikan pada pola anomali yang sudah sama antara anomali gayaberat regional hasil pemisahan anomali metode trend surface analysis dengan anomali regional hasil data sintetis. Pola anomali yang sama juga dapat dilihat pada anomali residual hasil pemisahan anomali metode trend surface analysis dengan anomali residual hasil data sintetis. Penerapan metode trend surface analysis pada data lapangan telah dilakukan dengan menghasilkan anomali regional dan anomali residual. Metode ini sangat baik dalam memisahkan anomali regional dan anomali residual terutama pada anomali regional yang berada pada kedalaman dalam

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A Gravity Survey of the Melville Island Ice Caps

Journal of Glaciology ◽

10.1017/s002214300001950x ◽

1966 ◽

Vol 6 (45) ◽

pp. 393-400 ◽

Cited By ~ 1

Author(s):

Allan Spector

Keyword(s):

Gravity Data ◽

Canadian Arctic ◽

Gravity Survey ◽

Canadian Arctic Archipelago ◽

Bouguer Anomalies ◽

Ice Caps ◽

Ice Cap ◽

Bedrock Geology ◽

Regional Gravity ◽

Made In

A gravity survey was made in June of 1963 of four ice caps on western Melville Island, Canadian Arctic Archipelago. Ice thicknesses were interpreted from Bouguer anomalies at 138 stations. The regional gravity field of the area has a simple form and is associated with a uniform bedrock geology. Because of this, the interpretation of the gravity data was greatly simplified in comparison with the more usual glaciological problem. It was found that greatest ice thicknesses ranged from 30 to 50 m., filling hidden valleys or depressions under the main ice-cap body. Ice-cap volumes ranged from 0.2 to 1.0 km.3.

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High-resolution regional gravity field modelling in a mountainous area from terrestrial gravity data

Geophysical Journal International ◽

10.1093/gji/ggw311 ◽

2016 ◽

Vol 207 (2) ◽

pp. 949-966 ◽

Cited By ~ 17

Author(s):

Blažej Bucha ◽

Juraj Janák ◽

Juraj Papčo ◽

Aleš Bezděk

Keyword(s):

High Resolution ◽

Gravity Field ◽

Gravity Data ◽

Mountainous Area ◽

Terrestrial Gravity ◽

Gravity Field Modelling ◽

Field Modelling ◽

Regional Gravity

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REGIONAL GRAVITY SURVEY OF PARTS OF TOOELE, JUAB, AND MILLARD COUNTIES, UTAH

Geophysics ◽

10.1190/1.1438338 ◽

1957 ◽

Vol 22 (1) ◽

pp. 48-61 ◽

Cited By ~ 2

Author(s):

J. Burlin Johnson ◽

Kenneth L. Cook

Keyword(s):

Bouguer Anomaly ◽

Gravity Anomalies ◽

Basin And Range ◽

Fault Zones ◽

Gravity Survey ◽

Gravity Gradients ◽

Northern Margin ◽

Eastern Margin ◽

Vertical Displacements ◽

Regional Gravity

In the summer of 1955 a regional gravity survey was made in parts of Tooele, Juab, and Millard Counties, Utah. A total of 455 gravity stations were occupied in an area of about 1,700 square miles. A Bouguer anomaly map was compiled with a contour interval of 2 milligals. Steep gravity gradients indicate major Basin and Range fault zones along the eastern margin of the Cedar Mountains, the southwestern margin of Davis Mountain and its associated outcrops, the northeastern margins of Camels Back Ridge and Simpson Buttes, the eastern margin of Granite Mountain, and the northern margin of the Dugway Range. The principal trend of these fault zones is northwesterly; and they were instrumental in partly outlining several of the mountain ranges in the surveyed area. Great graben with probable vertical displacements of at least several thousand feet were found east of Granite Mountain and northeast of Camels Back Ridge. The highest gravity values, which lie just northwest of Granite Mountain, are about 40 milligals higher than the surrounding surveyed region. Gravity anomalies transecting the Dugway and Thomas Ranges probably indicate pre‐Basin and Range faulting.

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Viticultural landscapes: Localised transformations over the past 150 years through an analysis of three case studies in Slovakia

Moravian Geographical Reports ◽

10.2478/mgr-2019-0012 ◽

2019 ◽

Vol 27 (3) ◽

pp. 155-168 ◽

Cited By ~ 2

Author(s):

Dagmar Štefunková ◽

Ján Hanušin

Keyword(s):

Land Cover ◽

Diversity Index ◽

Landscape Diversity ◽

Edge Density ◽

Entire Study ◽

The Past ◽

Grid Unit ◽

History Of ◽

Second Period ◽

Entire Study Area

Abstract The transformation of vineyard landscapes is evaluated in this article by assessing the changes in land cover and landscape diversity in selected study areas in two time periods – from 1867 to 1949, and from then to 2016. The study areas are characterised by a long history of viticulture and with important occurrences of old and new agrarian relief forms. Fine-scale land cover and landscape diversity analysis, as well as the study of historical and strategic documents, enabled an accurate interpretation of the viticultural landscape trajectories and their drivers. Landscape diversity was computed using the Shannon diversity index for each 625 square metre grid unit, and applying other metrics for the entire study area. Our research established that the study areas oscillated during this period between extensification and agricultural intensification, and the general trend confirmed the disappearance of traditional vineyards and a decline in modernised vineyard areas after socialism. Although extensification and intensification are seemingly contradictory processes, it is established that these both increase landscape diversity. In addition, landscape diversity changes in the second period are influenced more by changes in quantitative landscape pattern characteristics via edge density than qualitative patterns, e.g. patch richness, which reflect land use diversity.

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Application of the nonlinear optimisation in regional gravity field modelling using spherical radial base functions

Studia Geophysica et Geodaetica ◽

10.1007/s11200-020-1077-y ◽

2021 ◽

Author(s):

Hany Mahbuby ◽

Yazdan Amerian ◽

Amirhossein Nikoofard ◽

Mehdi Eshagh

Keyword(s):

Gravity Anomaly ◽

Gravity Field ◽

Fundamental Equation ◽

Physical Geodesy ◽

Gravity Anomalies ◽

Global Navigation Satellite Systems ◽

Disturbing Potential ◽

Gravity Field Model ◽

Regional Gravity ◽

Mean Square Errors

AbstractThe gravity field is a signature of the mass distribution and interior structure of the Earth, in addition to all its geodetic applications especially geoid determination and vertical datum unification. Determination of a regional gravity field model is an important subject and needs to be investigated and developed. Here, the spherical radial basis functions (SBFs) are applied in two scenarios for this purpose: interpolating the gravity anomalies and solving the fundamental equation of physical geodesy for geoid or disturbing potential determination, which has the possibility of being verified by the Global Navigation Satellite Systems (GNSS)/levelling data. Proper selections of the number of SBFs and optimal location of the applied SBFs are important factors to increase the accuracy of estimation. In this study, the gravity anomaly interpolation based on the SBFs is performed by Gauss-Newton optimisation with truncated singular value decomposition, and a Quasi-Newton method based on line search to solve the minimisation problems with a small number of iterations is developed. In order to solve the fundamental equation of physical geodesy by the SBFs, the truncated Newton optimisation is applied as the Hessian matrix of the objective function is not always positive definite. These two scenarios are applied on the terrestrial free-air gravity anomalies over the topographically rough area of Auvergne. The obtained accuracy for the interpolated gravity anomaly model is 1.7 mGal with the number of point-masses about 30% of the number of observations, and 1.5 mGal in the second scenario where the number of used kernels is also 30%. These accuracies are root mean square errors (RMSE) of the differences between predicted and observed gravity anomalies at check points. Moreover, utilising the optimal constructed model from the second scenario, the RMSE of 9 cm is achieved for the differences between the gravimetric height anomalies derived from the model and the geometric height anomalies from GNSS/levelling points.

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