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 (7) ◽  
pp. 1484-1485
Author(s):  
Zofia Mortimer
Keyword(s):  
Vertical Gradient ◽  
Density Contrast ◽  
Mine Workings ◽  
Gradient Measurements

In his paper Fajklewicz discusses the use of the gravity tower vertical gradient [Formula: see text] for the detection of small, shallow bodies that show a density contrast with the surroundings (geologic structures, caverns and old mine workings). The reasons given by the author for such application of [Formula: see text] are the properties of the gravity vertical gradient and the vast experience of many years.

GRAVITY VERTICAL GRADIENT MEASUREMENTS FOR THE DETECTION OF SMALL GEOLOGIC AND ANTHROPOGENIC FORMS

Geophysics ◽  
1976 ◽  
Vol 41 (5) ◽  
pp. 1016-1030 ◽  
Author(s):  
Zbigniew J. Fajklewicz
Keyword(s):  
Detailed Analysis ◽  
Research Work ◽  
Vertical Gradient ◽  
Industrial Applications ◽  
New Method ◽  
Topographic Correction ◽  
Engineering Problems ◽  
Mine Workings ◽  
The Difference ◽  
Gradient Measurements

The gravity tower vertical gradient has been applied to the solution of a number of important geologic, mining, and engineering problems, particularly to the search for and investigation of geologic structures and the detection of caverns and old mine workings. The effective application of the method depends upon recognizing the difference between the theoretical gravity vertical gradient [Formula: see text] and the gradient [Formula: see text] measured by means of a tower and gravimeter. The former is a derivative of the function g, the latter its differential quotient. Consequently, the differences between [Formula: see text] and [Formula: see text] in the same point may attain high values. Thus, e.g., for a sphere with a radius of 1 m, a density of 2.0 gm/cc and the depth of occurrence of its center equaling 1.2 m, the difference of the theoretical absolute amplitudes [Formula: see text] Eötvös units. Application of the method of the gravity tower vertical gradient on an industrial scale was possible due to the introduction of (1) a new design of the measuring tower, (2) detailed analysis of errors, and (3) a new method of calculating the topographic correction of the gravity vertical gradient. The paper sums up the results of five years of research work and industrial applications. During that period several thousand measurements of the gravity vertical gradient were made.

Magnitude of anomalies in the vertical gradient of gravity

Geophysics ◽  
1981 ◽  
Vol 46 (11) ◽  
pp. 1609-1610 ◽  
Author(s):  
Sigmund Hammer
Keyword(s):  
Vertical Gradient ◽  
Spherical Body ◽  
Density Contrast ◽  
Maximum Gradient ◽  
Maximum Value ◽  
Simple Mass ◽  
Spherical Mass ◽  
Vertical Gradient Of Gravity

The maximum gradient which can be caused by a simple mass is that of a spherical body. The equation for the vertical gradient at the point P above the center of a spherical mass of density contrast σ (see insert on Figure 1) can be written in the form [Formula: see text] where G is the universal gravity constant [Formula: see text] Expressing the gradient in the Eötvös units, we have [Formula: see text] In terms of percentage of the earth’s normal vertical gradient, the anomaly is [Formula: see text] of 3086 E°. At the surface of the sphere (h = 0), we have the maximum value [Formula: see text] of 3086 E° which is independent of the radius R.

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.

GRADIENT MEASUREMENTS IN AEROMAGNETIC SURVEYING

Geophysics ◽  
1965 ◽  
Vol 30 (5) ◽  
pp. 891-902 ◽  
Author(s):  
Peter Hood
Keyword(s):  
Optical Pumping ◽  
Vertical Gradient ◽  
Horizontal Distance ◽  
Total Field ◽  
Highly Sensitive ◽  
Geophysical Information ◽  
The Difference ◽  
Gradient Measurements ◽  
First Vertical Derivative ◽  
Depth Of Burial

The recent development of highly sensitive magnetometers, such as the optical‐pumping varieties, has made feasible the measurement of the first vertical derivative of the total field (∂ΔT/∂h) in aeromagnetic surveys. This is accomplished by using two sensitive magnetometer heads separated by a constant vertical distance, and recording the difference in outputs. The effect of diurnal is thus eliminated in the resultant differential output, and this is an especially desirable feature in northern Canada where the diurnal variation is usually much greater than is found in more southerly magnetic latitudes. Moreover, steeply dipping geological contacts in high‐magnetic latitudes are outlined by the resultant zero‐gradient contour. It is also possible to obtain the depth of burial of the contact from the graph of (∂ΔT/∂h) versus (x∂ΔT/∂x) where x is the horizontal distance measured from the contact. Similar quantitative interpretations may be made for the point pole and dipole. The data reduction necessary to produce a vertical‐gradient map is much simpler than with the total‐field case because no datum levelling is necessary. Since the aircraft track will be available from the main compilation it is only necessary to plot the resultant vertical‐gradient values on the track map and contour. Thus, two maps will be obtained for little more than the price of one but with a greatly increased gain in geophysical information concerning the geometry of the causative bodies. Actually, a first‐derivative map is difficult (and therefore costly) to produce by any other means. The measurement of the vertical gradient would appear to be the main advantage to using hundredth‐gamma magnetometers in aeromagnetic surveys, since those types presently in service are sensitive enough for the effective delineation of total‐field anomalies.

AN INTEGRATION TECHNIQUE FOR AIRBORNE GRAVITY GRADIENT MEASUREMENTS

Geophysics ◽  
1961 ◽  
Vol 26 (4) ◽  
pp. 474-479 ◽  
Author(s):  
Norman R. Paterson
Keyword(s):  
Plane Surface ◽  
Vertical Gradient ◽  
Gravity Force ◽  
Airborne Gravity ◽  
Gravity Gradient ◽  
Integration Technique ◽  
Simple Method ◽  
Gradient Measurements

For some purposes it may be desirable to work with the gravity force g rather than its vertical gradient g′. A simple method has been tested by which measurements of g′ on a plane surface can be integrated to produce values of g anywhere in space above the plane of measurement. The method appears to show promising results.

GRADIENT MEASUREMENTS IN GROUND MAGNETIC PROSPECTING

Geophysics ◽  
1965 ◽  
Vol 30 (3) ◽  
pp. 403-410 ◽  
Author(s):  
Peter Hood ◽  
D. J. McClure
Keyword(s):  
Contact Point ◽  
Vertical Component ◽  
Vertical Gradient ◽  
Horizontal Distance ◽  
Total Field ◽  
Gradient Measurements ◽  
Ground Magnetic ◽  
Vertical Contact ◽  
First Vertical Derivative ◽  
Depth Of Burial

The development of electronic magnetometers, i.e., the proton‐precession and fluxgate instruments, for use in ground magnetic surveys has permitted the measurement of the first‐vertical derivative of the total field, or of the vertical component of that field, with negligible addition to the total cost of the survey. The gain in information is, however, significant. Curves for the vertical gradient over a vertical contact, point pole, and finite dipole are presented. The vertical contact is outlined by the zero contour for the vertical gradient of the vertical component, and the depth of burial is half the horizontal distance between the positive and negative maxima. The depth of burial of the point pole and finite dipole is approximately equal to the horizontal distance between the negative half‐maximum points on the vertical‐gradient curves.

GRAVITY GRADIENTS AND THE INTERPRETATION OF THE TRUNCATED PLATE

Geophysics ◽  
1976 ◽  
Vol 41 (6) ◽  
pp. 1370-1376 ◽  
Author(s):  
John M. Stanley ◽  
Ronald Green
Keyword(s):  
Hilbert Transform ◽  
Theoretical Data ◽  
Vertical Gradient ◽  
Density Contrast ◽  
Horizontal Gradient ◽  
Gravity Gradients ◽  
Gravity Method ◽  
Commercially Important ◽  
Dip Angle ◽  
Vertical Gradients

The truncated plate and geologic contact are commercially important structures which can be located by the gravity method. The interpretation can be improved if both the horizontal and vertical gradients are known. Vertical gradients are difficult to measure precisely, but with modern gravimeters the horizontal gradient can be measured conveniently and accurately. This paper shows how the vertical gradient can be obtained from the horizontal gradient by the use of a Hilbert transform. A procedure is then presented which easily enables the position, dip angle, depth, thickness, and density contrast of a postulated plate to be precisely and unambiguously derived from a plot of the horizontal gradient against the vertical gradient at each point measured. The procedure is demonstrated using theoretical data.

scholarly journals Dynamics of nitrogen oxides and ozone above and within a mixed hardwood forest in Northern Michigan

2012 ◽  
Vol 12 (12) ◽  
pp. 32515-32564
Author(s):  
B. Seok ◽  
D. Helmig ◽  
L. Ganzeveld ◽  
M. W. Williams ◽  
C. S. Vogel
Keyword(s):  
Nitrogen Oxides ◽  
Climate Model ◽  
Turbulent Transport ◽  
Vertical Gradient ◽  
Early Morning ◽  
Daily Maximum ◽  
Canopy Exchange ◽  
Mixing Ratios ◽  
Leaf Level ◽  
Gradient Measurements

Abstract. The dynamic behavior of nitrogen oxides (NOx = NO + NO2) and ozone (O3) above and within the canopy at the University of Michigan Biological Station AmeriFlux (UMBS Flux) site was investigated by continuous multi-height vertical gradient measurements during the summer and the fall of 2008. A daily maximum in nitric oxide (NO) levels was consistently observed during the morning hours between 06:00 and 09:00 EST above the canopy. Daily NO maxima ranged between 0.2 and 2 ppbv (with a median of 0.3 ppbv), which was 2 to 20 times above its atmospheric background. The sources and causes of this NO maximum were evaluated using NOx and O3 measurements and synoptic and micrometeorological data. This analysis was further supported by numerical simulations with a multi-layer canopy exchange model implemented into a single-column chemistry-climate model. The observations indicated that the morning NO maximum was caused by the photolysis of NO2 from non-local air masses, which were transported into the canopy from aloft during the morning breakup of the nocturnal boundary layer. The analysis of simulated process tendencies indicated that the downward turbulent transport of NOx into the canopy compensates for the removal of NOx through chemistry and dry deposition. The sensitivity of NOx and O3 concentrations on soil and foliage NOx emissions was also assessed with the model. Uncertainties associated with the emissions of NOx from the soil or from leaf-surface nitrate photolysis did not explain the observed diurnal behavior in NOx (and O3), and in particular, the morning NOx peak mixing ratio. However, when considering the existence of a NO2 compensation point, an increase in the early morning NOx and NO peak mixing ratios by ~30% was simulated. This increase suggests the potential importance of leaf-level, bi-directional exchange of NO2 in understanding the observed temporal variability in NOx at UMBS.

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

Geophysics ◽  
1977 ◽  
Vol 42 (5) ◽  
pp. 1066-1067
Author(s):  
Avner A. Arzi
Keyword(s):  
Ground Surface ◽  
Vertical Gradient ◽  
Powerful Method ◽  
Gravity Measurements ◽  
The Difference ◽  
Gradient Measurements ◽  
Tower Height

Microgravimetry is indeed a powerful method for the detection of many small geologic and anthropogenic bodies (Arzi, 1975). Fajklewicz essentially advocates a particular procedure for microgravimetric surveys. Whereas gravity measurements are usually performed at the ground surface, Fajklewicz simultaneously performs measurements also at a surface situated 3 m above ground, using a portable tower. His data are presented as a map of the difference between the bottom and the top measurements. This difference (which may be measured in gradient units after being divided by the tower height) is called the Gravity Tower Vertical Gradient (GTVG). Similar procedures have been occasionally employed for various purposes (Thyssen‐Bornemisza, 1976). My main comments on the paper by Fajklewicz are as follows.

scholarly journals Evaluation of mafic dyke swarm continuity under the Joaquina dune field with ground magnetic survey

2017 ◽  
Vol 47 (2) ◽  
pp. 237-247 ◽  
Author(s):  
George Caminha-Maciel ◽  
Marcia Ernesto ◽  
Welitom R. Borges ◽  
Junior Bresolin ◽  
Reginaldo Lemos
Keyword(s):  
Vertical Gradient ◽  
Crystalline Basement ◽  
Dyke Swarm ◽  
Magnetic Survey ◽  
The North ◽  
Magnetic Signature ◽  
Mafic Dyke Swarm ◽  
Gradient Measurements ◽  
Ground Magnetic ◽  
North And South

ABSTRACT: A ground magnetic survey in a Central-East area of the Santa Catarina Island tested the continuity of the Cretaceous mafic dykes beneath the aeolic sediments of the Joaquina plain. Vertical gradient measurements taken in 1880 stations did not detect any magnetic anomaly related to subsurface dykes. Four magnetic profiles located to the north and south of the main area showed the magnetic signature of various dykes some of them already mapped (north profiles), but also some in subsurface (south profiles). These results suggest that the dykes probably were shallow and truncated, and were already eroded along with the crystalline basement.

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