POSSIBLE APPLICATION OF THE ANOMALOUS FREE‐AIR VERTICAL GRADIENT TO MARINE EXPLORATION

Geophysics ◽  
1966 ◽  
Vol 31 (1) ◽  
pp. 260-263
Author(s):  
Stephen Thyssen‐Bornemisza
Keyword(s):  
Vertical Cylinder ◽  
Vertical Gradient ◽  
Gravity Gradient ◽  
Average Gradient ◽  
Vertical Gravity Gradient ◽  
Free Air ◽  
Vertical Gravity ◽  
Lithologic Unit ◽  
Marine Exploration ◽  
Anomalous Average

Recently it could be shown (Thyssen‐Bornemisza, 1965) that a vertical lithologic unit cylinder generates a relatively strong anomalous free‐air vertical gravity gradient F′ along the cylinder axis. The following simple example may serve as a demonstration. A small vertical cylinder made of gold or tungsten, where radius r and length L are identical, would generate the anomalous average gradient F′∼3,223 Eötvös units over the interval h=r=L going from the cylinders top surface upward. Suppose r=l=1 cm, then an average gradient exceeding the earth’s normal free‐air vertical gradient F is present over the interval h=1 cm.

On: “The anomalous vertical gradient of gravity” by Sigmund Hammer (GEOPHYSICS, February 1970, p. 153–157).

Geophysics ◽  
1971 ◽  
Vol 36 (1) ◽  
pp. 214-216 ◽  
Author(s):  
Stephen Thyssen‐Bornemisza
Keyword(s):  
Horizontal Plane ◽  
Vertical Gradient ◽  
Observation Point ◽  
Gravity Gradient ◽  
Vertical Gravity Gradient ◽  
Free Air ◽  
Plane Passing ◽  
Vertical Gravity ◽  
Vertical Gradient Of Gravity

The interesting analysis by Hammer seems to be founded partly on the approach of Heiskanen and Moritz (1967), in which a real gravity and a vertical gravity gradient are correlated according to the relation [Formula: see text] Here Δg denotes the free‐air anomalies on a horizontal plane passing through observation point p and [Formula: see text] is the anomaly at p, the latter representing the center of the (x, y) coordinates.

VERTICAL GRADIENT OF GRAVITY ON AXIS FOR HOLLOW AND SOLID CYLINDERS

Geophysics ◽  
1966 ◽  
Vol 31 (4) ◽  
pp. 816-820 ◽  
Author(s):  
Thomas A. Elkins
Keyword(s):  
Hollow Cylinder ◽  
Sudden Change ◽  
Vertical Gradient ◽  
Outer Radius ◽  
Gravity Gradient ◽  
Gradient Effect ◽  
Vertical Gravity Gradient ◽  
Vertical Gravity ◽  
Special Case ◽  
Vertical Gradient Of Gravity

The recent interest in borehole gravimeters and vertical gravity gradient meters makes it worthwhile to analyze the simple case of the vertical gravity gradient on the axis of a hollow cylinder, simulating a borehole. From the viewpoint of potential theory the results are interesting because of the discontinuities which may occur when a vertical gradient profile crosses a sudden change in density. Formulas for the vertical gradient effect are given for observations above, inside, and below a hollow cylinder and a solid cylinder. The special case of an infinitely large outer radius for the cylinders is also considered, leading to formulas for the vertical gradient effect inside a borehole on its axis and inside a horizontal slab. Some remarks are made on the influence of the shape of a buried vertical gradient meter on the correction factor for changing the meter reading to density.

On: “Gravity vertical gradient measurements for the detection of small geologic and anthropogenic forms” by Z. J. Fajklewicz (GEOPHYSICS, October 1976, p. 1016–1030)

Geophysics ◽  
1977 ◽  
Vol 42 (4) ◽  
pp. 872-873
Author(s):  
Stephen Thyssen‐Bornemisza
Keyword(s):  
Research Work ◽  
Vertical Gradient ◽  
Gravity Gradient ◽  
Wind Gust ◽  
Near Surface ◽  
New Methods ◽  
Vertical Gravity Gradient ◽  
Surface Variation ◽  
Gradient Measurements ◽  
Vertical Gravity

In his paper, Fajklewicz discusses the improvement of vertical gravity gradient measurements arising from a very stable tower apparently not affected by wind gust vibration and climatic changes. Further, the lower plate where the gravity meter is resting can be changed in position to avoid possible disturbances from surface and near‐surface variation, and new methods for correcting and interpreting observed gradients over the vertical interval of about 3 m are presented. Some 1000 field stations were observed, including research work and industrial application.

Vertical gravity gradient surveys: Field results and interpretations in British Columbia, Canada

Geophysics ◽  
1982 ◽  
Vol 47 (6) ◽  
pp. 919-925 ◽  
Author(s):  
Charles A. Ager ◽  
Jacques O. Liard
Keyword(s):  
British Columbia ◽  
Field Conditions ◽  
Gravity Gradient ◽  
Mountainous Terrain ◽  
Coal Deposit ◽  
Vertical Gravity Gradient ◽  
Free Air ◽  
Vertical Gravity ◽  
Mining Exploration ◽  
Air Effect

Two vertical gravity gradient (VGG) surveys were completed by the authors during 1977 in British Columbia, Canada. The VGG method utilizes a LaCoste and Romberg model D gravity meter in conjunction with a small gradient tripod. The VGG method is practical under most field conditions using a 2 person crew and yields results precise to ±20 E or better. The VGG work indicates that the “free‐air” effect ranges between 2600–2800 E for southwestern British Columbia, which is somewhat lower than the theoretical value of 3086 E. The usefulness of the method in mining exploration is doubtful, especially in hilly or mountainous terrain where VGG values are shown to be very terrain sensitive. However, the importance of knowing the regional VGG variations is emphasized by the work over the Hat Creek coal deposit, British Columbia.

On: “Variations of Vertical Gravity Gradient in New York City and Alpine, New Jersey” by John T. Kuo, Mario Ottaviani, and Shri K. Singh (GEOPHYSICS, April 1969, p. 235–248).

Geophysics ◽  
1970 ◽  
Vol 35 (3) ◽  
pp. 521-522 ◽  
Author(s):  
Stephen Thyssen-Bornemisza
Keyword(s):  
New York ◽  
New York City ◽  
New Jersey ◽  
York City ◽  
Vertical Gradient ◽  
Gravity Gradient ◽  
Vertical Gravity Gradient ◽  
Vertical Gravity

In their paper, Kuo et al, following the footsteps of Hammer (1938), reported interesting vertical gradient observations in high buildings with a gravity meter. However, conclusion (5) drawn by Kuo et al should be discussed briefly in order to avoid an incorrect impression.

scholarly journals Analysis of Groundwater Decline and Land Subsidence by using of Microgravity and Vertical Gravity Gradient Over Time Method

2014 ◽  
Vol 15 (1) ◽  
pp. 7 ◽  
Author(s):  
Suhayat Minardi ◽  
Hiden Hiden ◽  
Daharta Dahrin ◽  
Mahmud Yusuf
Keyword(s):  
Gravity Anomaly ◽  
Land Subsidence ◽  
Gravity Data ◽  
Vertical Gradient ◽  
Time Lapse ◽  
Gravity Gradient ◽  
Vertical Gravity Gradient ◽  
Vertical Gravity ◽  
Groundwater Decline ◽  
Over Time

Studies have been conducted to identify the occurrence of subsidence, a decline of groundwater, and to model the causes of subsidence in areas of Jakarta based on response of microgravity anomaly and vertical gravity gradient over time. Based on the processing and interpretation of gravity data advance of the time concluded that by using a combination of time lapse microgravity and its vertical gradient have been able to localize the source of the gravity anomaly and the results are strongly support the results of filtering to separate the source of the anomaly. The subsidence that occurs predominantly due to resettlement (in West and North Jakarta), caused by the extraction of groundwater and resettlement (in Central and East Jakarta), and dominated due to the extraction of groundwater (in South Jakarta).Keywords : Groundwater, time lapse micogravity, time lapse vertical gradient, resettlement, subsidence

OBSERVATION OF THE VERTICAL GRADIENT OF GRAVITY IN THE FIELD

Geophysics ◽  
1956 ◽  
Vol 21 (3) ◽  
pp. 771-779 ◽  
Author(s):  
Stephen Thyssen‐Bornemisza ◽  
W. F. Stackler
Keyword(s):  
Vertical Gradient ◽  
Gravity Gradient ◽  
Field Observations ◽  
Vertical Gravity Gradient ◽  
Vertical Gravity ◽  
Vertical Gradient Of Gravity

Field observations of the anomalous vertical gravity gradient were made at Houston, Texas, and over the Turner Valley structure near Calgary, Alberta, Canada. The results obtained are encouraging, but the precision of the measurements was to some extent reduced by vibrations generated in transporting the gravimeter up and down the tripod, as well as by gusts of wind.

Experimental determination of the vertical gravity gradient below the sea level

2016 ◽  
Vol 52 (6) ◽  
pp. 866-868 ◽  
Author(s):  
L. K. Zheleznyak ◽  
V. N. Koneshov ◽  
P. S. Mikhailov
Keyword(s):  
Experimental Determination ◽  
Sea Level ◽  
Gravity Gradient ◽  
Vertical Gravity Gradient ◽  
Vertical Gravity

Seafloor topography variations mapped by regional gravity tensor analysis 

2021 ◽  
Author(s):  
Lucia Seoane ◽  
Guillaume Ramillien ◽  
José Darrozes ◽  
Frédéric Frappart ◽  
Didier Rouxel ◽  
...  
Keyword(s):  
New England ◽  
Static Field ◽  
Gravity Gradient ◽  
Seafloor Topography ◽  
Central Pacific ◽  
Goce Mission ◽  
Vertical Gravity Gradient ◽  
Seamount Chain ◽  
Vertical Gravity ◽  
Regional Gravity

<p>The AGOSTA project initially proposed by our team and lately funded by CNES TOSCA consists of developing efficient approaches to restore seafloor shape (or bathymetry), as well as lithospheric parameters such as the crust and elastic thicknesses, by combining different types of observations including gravity gradient data. As it is based on the second derivatives of the potential versus the space coordinates, gravity gradiometry provides more information inside the Earth system at short wavelengths. The GOCE mission has measured the gravity gradient components of the static field globally and give the possibility to detect more details on the structure of the lithosphere at spatial resolutions less than 200 km. We propose to analyze these satellite-measured gravity tensor components to map the undersea relief more precisely than using geoid or vertical gravity previously considered for this purpose. Inversion of vertical gravity gradient data derived from the radar altimetry technique also offers the possibility to reach greater resolutions (at least 50 km) than the GOCE mission one. The seafloor topography estimates are tested in areas well-covered by independent data for validation, such as around the Great Meteor guyot [29°57′10.6″N, 28°35′31.3″W] and New England seamount chain [37°24′N 60°00′W, 120° 10' 30.4" W] in the Atlantic Ocean as well as the Acapulco seamount [13° 36' 15.4" N, 120° 10' 30.4" W] in the Central Pacific.</p>

Reduction to the pole of the North American magnetic anomalies

Geophysics ◽  
1990 ◽  
Vol 55 (2) ◽  
pp. 218-225 ◽  
Author(s):  
J. Arkani‐Hamed ◽  
W. E. S. Urquhart
Keyword(s):  
North America ◽  
Gravity Anomalies ◽  
Magnetic Anomalies ◽  
Gravity Gradient ◽  
Plate Boundaries ◽  
Gravity Gradients ◽  
The North ◽  
Vertical Gravity Gradient ◽  
Regional Tectonic ◽  
Vertical Gravity

Magnetic anomalies of North America are reduced to the pole using a generalized technique which takes into account the variations in the directions of the core field and the magnetization of the crust over North America. The reduced‐to‐the‐pole magnetic anomalies show good correlations with a number of regional tectonic features, such as the Mid‐Continental rift and the collision zones along plate boundaries, which are also apparent in the vertical gravity gradient map of North America. The magnetic anomalies do not, however, show consistent correlation with the vertical gravity gradients, suggesting that magnetic and gravity anomalies do not necessarily arise from common sources.

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