Analysis on Bouguer Gravity Anomaly Characteristics and Boundary Identification in China and Surrounding Regions

Abstract China is located in the southeast of the Eurasian Plate and is subject to the effects of subducting, squeezing and collision by the Pacific Plate to the east, Philippine Plate to the southeast and Indian Ocean Plate to the southwest. It has exceptional geotectonic structure. Based on the satellite gravity data with high precision, high resolution and ample geophysical information, combined with geological data, by using satellite gravity potential field and its full tensor gradient, this paper studies the distribution characteristics of gravity anomalies and the identification of tectonic boundaries in China and surrounding regions. Results suggest that the Bouguer gravity anomaly in eastern China reduces gradually from east to west, mostly in the direction of NNE; in the western, it reduces gradually in a wave mode from north to south, mainly in the directions of NW and NWW. In general, the stress field reduces gradually from west to east, and the tectonic of stress field in western China is complex. The maximum principal compressive stress in Xinjiang exists in SN direction and that in Qinghai-Tibet Plateau mostly changes gradually from NNE to SSE; the change in eastern China is relatively simple, and the maximum principal compressive stress direction gradually changes from NE to WE and then to SE. In addition to the above study results, by comprehensively referencing the previous studies by other people and by using the boundary identification methods based on the satellite gravity full-tensor gradient data and its combinations, we update the extension route of Red River fault zone and deduce the tectonic unit boundary between the North China and South China active tectonic block regions. This paper identifies in China and surrounding regions 6 primary active tectonic blocks, 22 secondary active tectonic blocks, 3 tertiary active tectonic blocks and the 20 active tectonic block boundary zones constituted of deformation belts and active tectonic belts with various geometric structures and width variations. The results of this study can improve the understanding of gravity anomalies and boundary structures in China and surrounding regions, and provide certain geophysical supports for geological structure analysis and crustal dynamic process.

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Usporedba različitih pristupa Bouguer-ove redukcije na temelju satelitskih gravimetrijskih podataka

Geofizika ◽

10.15233/gfz.2020.37.7 ◽

2020 ◽

Vol 37 (2) ◽

pp. 237-261

Author(s):

Fan Luo ◽

Xin Tao ◽

Guangming Fu ◽

Chong Zhang ◽

Kun Zhang ◽

...

Keyword(s):

Gravity Anomaly ◽

Gravity Data ◽

Gravity Anomalies ◽

Gravitational Effect ◽

Seismic Profile ◽

Bouguer Gravity ◽

Seismic Profiles ◽

Satellite Gravity ◽

Free Air ◽

Free Air Gravity

Satellite gravity data are widely used in the field of geophysics to study deep structures at the regional and global scales. These data comprise free-air gravity anomaly data, which usually need to be corrected to a Bouguer gravity anomaly for practical application. Bouguer reduction approaches can be divided into two methods based on the coordinate system: the spherical coordinates method (SBG) and the Cartesian coordinates method; the latter is further divided into the CEBG and CBG methods, which do and do not include the Earth’s curvature correction. In this paper, free-air gravity anomaly data from the eastern Tibetan Plateau and its adjacent areas were used as the basic data to compare the CBG, CEBG, and SBG Bouguer gravity correction methods. The comparison of these three Bouguer gravity correction methods shows that the effect of the Earth’s curvature on the gravitational effect increases with increasing elevation in the study area. We want to understand the inversion accuracy for the data obtained by different Bouguer gravity reduction approaches. The depth distributions of the Moho were obtained by the interface inversion of the Bouguer gravity anomalies obtained by the CBG, CEBG, and SBG, and active seismic profiles were used as references for comparison and evaluation. The results show that the depths of the Moho obtained by the SBG inversion are more consistent with the measured seismic profile depths. Therefore, the SBG method is recommended as the most realistic approach in the process of global or regional research employing gravity data.

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On the topographic effects by Stokes’ formula

Journal of Geodetic Science ◽

10.2478/jogs-2014-0014 ◽

2014 ◽

Vol 4 (1) ◽

Cited By ~ 1

Author(s):

L.E. Sjöberg

Keyword(s):

Gravity Anomaly ◽

Bouguer Anomaly ◽

Gravity Anomalies ◽

Geoid Height ◽

Topographic Effects ◽

Gravimetric Geoid ◽

Bouguer Gravity ◽

The Third ◽

Stokes Formula ◽

The Difference

AbstractTraditional gravimetric geoid determination relies on Stokes’ formula with removal and restoration of the topographic effects. It is shown that this solution is in error of the order of the quasigeoid-to-geoid difference, which is mainly due to incomplete downward continuation (dwc) of gravity from the Earth’s surface to the geoid. A slightly improved estimator, based on the surface Bouguer gravity anomaly, is also biased due to the imperfect harmonic dwc the Bouguer anomaly. Only the third estimator,which uses the (harmonic) surface no-topography gravity anomaly, is consistent with the boundary condition and Stokes’ formula, providing a theoretically correct geoid height. The difference between the Bouguer and no-topography gravity anomalies (on the geoid or in space) is the “secondary indirect topographic effect”, which is a necessary correction in removing all topographic signals.

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

Geophysics ◽

10.1190/1.1443041 ◽

1991 ◽

Vol 56 (2) ◽

pp. 279-283 ◽

Cited By ~ 22

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.

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GRAVITY ANOMALY ASSESSMENT USING GGMS AND AIRBORNE GRAVITY DATA TOWARDS BATHYMETRY ESTIMATION

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xlii-4-w1-287-2016 ◽

2016 ◽

Vol XLII-4/W1 ◽

pp. 287-297

Author(s):

A. Tugi ◽

A. H. M. Din ◽

K. M. Omar ◽

A. S. Mardi ◽

Z. A. M. Som ◽

...

Keyword(s):

Gravity Anomaly ◽

Gravity Field ◽

Ocean Circulation ◽

Gravity Data ◽

Gravity Anomalies ◽

Airborne Gravity ◽

Satellite Gravity ◽

Earth’S Gravity Field ◽

Explorer Mission ◽

Satellite Gravity Missions

The Earth’s potential information is important for exploration of the Earth’s gravity field. The techniques of measuring the Earth’s gravity using the terrestrial and ship borne technique are time consuming and have limitation on the vast area. With the space-based measuring technique, these limitations can be overcome. The satellite gravity missions such as Challenging Mini-satellite Payload (CHAMP), Gravity Recovery and Climate Experiment (GRACE), and Gravity-Field and Steady-State Ocean Circulation Explorer Mission (GOCE) has introduced a better way in providing the information on the Earth’s gravity field. From these satellite gravity missions, the Global Geopotential Models (GGMs) has been produced from the spherical harmonics coefficient data type. The information of the gravity anomaly can be used to predict the bathymetry because the gravity anomaly and bathymetry have relationships between each other. There are many GGMs that have been published and each of the models gives a different value of the Earth’s gravity field information. Therefore, this study is conducted to assess the most reliable GGM for the Malaysian Seas. This study covered the area of the marine area on the South China Sea at Sabah extent. Seven GGMs have been selected from the three satellite gravity missions. The gravity anomalies derived from the GGMs are compared with the airborne gravity anomaly, in order to figure out the correlation (R<sup>2</sup>) and the root mean square error (RMSE) of the data. From these assessments, the most suitable GGMs for the study area is GOCE model, GO_CONS_GCF_2_TIMR4 with the R<sup>2</sup> and RMSE value of 0.7899 and 9.886 mGal, respectively. This selected model will be used in the estimating the bathymetry for Malaysian Seas in future.

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THE CORRELATION BETWEEN PRE‐CAMBRIAN ROCK DENSITIES AND BOUGUER GRAVITY ANOMALIES NEAR PARRY SOUND, ONTARIO

Geophysics ◽

10.1190/1.1437974 ◽

1954 ◽

Vol 19 (1) ◽

pp. 76-88

Author(s):

C. H. G. Oldham

Keyword(s):

Gravity Anomaly ◽

Gravity Anomalies ◽

Canadian Shield ◽

Gravity Survey ◽

Uniform Density ◽

Bouguer Gravity ◽

Geological Evidence ◽

Bouguer Gravity Anomaly ◽

Bouguer Gravity Anomalies

A gravity survey and a survey of rock densities have been carried out over an area of two thousand square miles near Parry Sound. A closed positive Bouguer gravity anomaly of thirty milligals was delineated, and a considerable variation was found to exist in the densities of pre‐Cambrian gneisses. In most previous interpretations of gravity over the Canadian Shield the gneisses have been assumed to possess a uniform density and anomalies have been attributed to changes in the thickness of horizontal crustal layers. In this paper it is shown that the Parry Sound anomaly can be explained in terms of structures within the crust taking the form of projections downward of the density variations found at the surface. The postulated structure is a nearly circular basin of dense gneisses. The shape is reasonable and agrees with such geological evidence as is available.

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Gravity anomalies of the United Arab Emirates: Implications for basement structures and infra-Cambrian salt distribution

GeoArabia ◽

10.2113/geoarabia1901143 ◽

2014 ◽

Vol 19 (1) ◽

pp. 143-158

Author(s):

Mohammed Y. Ali ◽

Anthony B. Watts ◽

Asam Farid

Keyword(s):

Gravity Anomaly ◽

United Arab Emirates ◽

Gravity Anomalies ◽

Abu Dhabi ◽

Fault System ◽

Bouguer Gravity ◽

Thrust Belt ◽

Bouguer Gravity Anomaly ◽

Fold And Thrust Belt ◽

Semail Ophiolite

ABSTRACT Gravity measurements onshore and offshore of the United Arab Emirates (UAE) have been used to construct a new Bouguer gravity anomaly map of the region. The gravity data, which has been gridded at 2,700 m × 2,700 m interval, has been used to constrain the tectonic elements, major lineation trends and structures of the Neoproterozoic basement of the Arabian Plate and the distribution of infra-Cambrian salt basins. Advanced transformation techniques (including first vertical derivative, total horizontal derivative, tilt derivative and Euler deconvolution) were applied to identify gravity source edges as an aid to structural interpretation and geological modelling of the study area. Three major structural provinces (fold-and-thrust belt, foreland and salt tectonic provinces) were identified based on the residual Bouguer gravity anomaly field. The eastern fold-and-thrust belt province is associated with short-wavelength positive gravity anomalies, which are attributed to the allochthonous series of the Semail Ophiolite and its related thrust sheets. The central foreland basin province is characterised by NNW-oriented negative gravity anomalies associated with deepening of the basement and thickening of Aruma and Pabdeh sediments in the foredeep basins and flexure of the top and base of the crust by the load of the Semail Ophiolite. The western salt tectonic province displays well-defined local gravity lows superimposed on a regional gravity high, which probably reflects the swelling of infra-Cambrian salt above a shallowing of the basement and thinning of the foredeep sediments. In addition, gravity modelling constrained by seismic and well data indicates the presence of substantial infra-Cambrian salt bodies in all basins of the UAE both onshore and offshore including the southern area of the Rub’ Al-Khali Basin. An extensive array of previously unmapped N-S, NW- and SW-trending lineaments affecting the basement and possibly overlying sediments are mapped in the UAE. The N-S Arabian trending lineament represents the effect of a major structure, along which many important oilfields are located (e.g. Bu Hasa). The SW trend has regular spacing and is dominant in the southern and central part of Abu Dhabi, east of the Falaha syncline. The NW-SE lineament is the most striking and includes two well-defined trends that cross Abu Dhabi Emirate, which in this paper are named as the Abu Dhabi Lineaments. These lineaments are associated with a linear gravity high extending from the southwestern border with Oman to the offshore close to Zakum oilfield. They are probably related to the Najd Fault System.

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THE USE OF THE LOGARITHMIC IMAGE PROCESSING APPLIED TO ANALYSING BOUGUER GRAVITY ANOMALY MAP (TANGIER-TETUAN’S AREA -MOROCCO)

Nexo Revista Científica ◽

10.5377/nexo.v28i2.3479 ◽

2017 ◽

Vol 28 (2) ◽

pp. 97-107

Author(s):

Saad Bakkali

Keyword(s):

Image Processing ◽

Gravity Anomaly ◽

Gravity Anomalies ◽

Image Process ◽

Bouguer Gravity ◽

Potential Field Data ◽

Bouguer Gravity Anomaly ◽

Logarithmic Image Processing ◽

Anomaly Map ◽

Classical Image

Image processing is a powerful tool for the enhancement of edges in images used in the interpretation of geophysical potential field data. Arial and terrestrial gravimetric surveys were carried out in the region of Tangier-Tetuan. From the observed and measured data of gravity Bouguer gravity anomalies map was prepared. This paper reports the results and interpretations of the transformed maps of Bouguer gravity anomaly of the Tangier-Tetuan area using the logarithmic image processing. Filtering analysis based on classical image process was applied. Operator image process like the logarithmic operator and the associated gamma correction tool are used. This paper also present the results obtained from this image processing analysis of the enhancement edges of the Bouguer gravity anomaly map of the Tangier-Tetuan zone.

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Geophysical interpretation of the Torngat orogen along the North River – Nutak transect, Labrador

Canadian Journal of Earth Sciences ◽

10.1139/e94-064 ◽

1994 ◽

Vol 31 (4) ◽

pp. 722-727 ◽

Cited By ~ 10

Author(s):

Tomas Feininger ◽

Ingo Ermanovics

Keyword(s):

Gravity Anomaly ◽

Gravity Anomalies ◽

Canadian Shield ◽

Bouguer Gravity ◽

Dimensional Model ◽

Prismatic Body ◽

Western Margin ◽

Geological Interpretation ◽

The North ◽

Geophysical Interpretation

A 19.3 mGal (1 Gal = 1 cm/s2) positive Bouguer gravity anomaly and a broad aeromagnetic low coincide with the Tasiuyak domain of the early paleo-Proterozoic Torngat orogen. The domain evolved during the collision of the western margin of the Archean Nain Province with an inferred, eastward-facing, platform-to-rise, sedimentary wedge sited on a proto-continent of Churchill (Rae) Province.A density contrast of +0.065 g∙cm−3 was measured between rocks of the Tasiuyak domain and those of the flanking Lac Lomier complex of the orogen and Nain Province. Using this contrast, a two and one-half dimensional model shows that rocks of Tasiuyak domain constitute a triangular prismatic body with maximum thickness of 13 km adjacent to Nain Province, which thins westward to a feather edge. The model is compatible, qualitatively, with the aeromagnetic anomaly and consonant with geological interpretation of an eastward-facing and thickening continental slope deposit. Deep exhumation of the Torngat orogen may account for the absence of paired gravity anomalies characteristic of many sutures elsewhere in the Canadian Shield.

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