en>Walrus068: removed big tags

2013-12-10T16:34:41Z

removed big tags

← Older revision		Revision as of 18:34, 10 December 2013
Line 1:		Line 1:
	~~Introduction! I am Dalton~~. ~~Acting~~ is a ~~thing that I appreciate totally addicted~~ to. ~~Vermont~~ is ~~literally~~ where ~~my home~~ is ~~certainly~~. ~~Managing everyone has been my big day job~~ for a ~~even while but I plan at changing it~~. I'~~ve been toiling on my website during some time now~~. ~~Visit it out here~~: http://~~prometeu~~.~~net<br><br>Also visit my page~~ :: [http://~~prometeu~~.~~net clash~~ of ~~clans hack no survey download~~]		In [[geodesy]] and [[geophysics]], the '''Bouguer anomaly''' (named after [[Pierre Bouguer]]) is a [[gravity anomaly]], corrected for the height at which it is measured and the attraction of terrain. The height correction alone gives a [[free-air gravity anomaly]].

			[[Image:Nj cboug.jpg\|thumb\|right\|Bouguer anomaly map of the state of [[New Jersey]] (USGS)]]

			==Anomaly==
			The Bouguer anomaly is related to the observed gravity <math>g_{obs}</math> as follows:

			:<math> g_B = g_{obs} - g_\lambda + \delta g_F - \delta g_B</math>
			:<math>g_B = g_{F} - \delta g_B</math>

			Here, <math>g_B</math> is the Bouguer anomaly, <math>g_F</math> is the free-air gravity anomaly, <math>g_\lambda</math> is the correction for latitude (because the Earth is not a perfect sphere) and <math>\delta g_F</math> is the free-air correction and <math>\delta g_B</math> is the correction for terrain called the ''Bouguer reduction''.

			A Bouguer reduction is called ''simple'' or ''incomplete'' if the terrain is approximated by an infinite flat plate called the ''Bouguer plate''. ''refined'' or ''complete'' Bouguer reduction removes the effects of terrain precisely. The difference between the two, the differential gravitational effect of the unevenness of the terrain, is called the ''terrain effect''. It is always negative.<ref name=Hofmann>{{harvnb\|Hofmann-Wellenhof\|Moritz\|2006\|loc=Section 3.4}}</ref>

			==Simple reduction==
			The gravitational acceleration <math>g</math> outside a Bouguer plate is perpendicular to the plate and towards it, with magnitude ''2πG'' times the mass per unit area, where <math>G</math> is the [[gravitational constant]]. It is independent of the distance to the plate (as can be proven most simply with [[Gauss's law for gravity]], but can also be proven directly with [[Newton's law of universal gravitation\|Newton's law of gravity]]). The value of <math>G</math> is 6.67 × 10<sup>−11</sup> N m² kg<sup>−2</sup>, so <math>g</math> is 4.191 × 10<sup>−10</sup> N m² kg<sup>−2</sup> times the mass per unit area. Using 1 [[Gal (unit)\|Gal]] = 0.01 m/s² we get 4.191 × 10<sup>−5</sup> mGal m² kg<sup>−1</sup> times the mass per unit area. For mean [[Rock (geology)\|rock]] [[density]] (2.67 g/cm³) this gives 0.1119 mGal/m.

			The Bouguer reduction for a Bouguer plate of thickness <math>\scriptstyle H</math> is
			:<math> \delta g_B = 2\pi\rho G H, </math>
			where <math>\rho</math> is the density of the material and <math>G</math> is the constant of gravitation.<ref name=Hofmann/> On Earth the effect on gravity of elevation is 0.3086 mGal/m decrease when going up, minus the gravity of the Bouguer plate, giving the ''Bouguer gradient'' of 0.1967 mGal/m.

			More generally, for a [[mass distribution]] with the density depending on one Cartesian coordinate ''z'' only, gravity for any ''z'' is 2π''G'' times the difference in mass per unit area on either side of this ''z'' value. A combination of two equal parallel infinite plates does not produce any gravity inside.

			== See also ==
			{{div col}}
			* [[Earth's gravity]]
			* [[Physical geodesy]]
			* [[Potential theory]]
			* [[Vertical deflection]]
			{{div col end}}

			==Notes==
			{{Reflist}}

			== References ==
			*{{cite book
			\|last = Lowrie
			\|first = William
			\|title = Fundamentals of Geophysics
			\|publisher = [[Cambridge University Press]]
			\|date = 2004
			\|isbn=0-521-46164-2
			}}
			*{{cite book
			\|last = Hofmann-Wellenhof
			\|first = Bernard
			\|last2 = Moritz
			\|first2 = Helmut
			\|title = Physical Geodesy
			\|publisher = [[Springer Science+Business Media\|Springer]]
			\|date = 2006
			\|edition = 2nd.
			\|isbn=978-3-211-33544-4
			}}

			== External links ==
			* [http://www.astro.oma.be/D1/GRAVIMETRY/gravboug.html Bouguer anomalies of Belgium. The blue regions are related to deficit masses in the subsurface]
			* [http://tin.er.usgs.gov/gravity/bouguer/ Bouguer gravity anomaly grid for the conterminous US] by the [United States Geological Survey].
			* [http://www.antarctica.ac.uk/documents/bas_bulletins/bulletin22_07.pdf Bouguer anomaly map of Grahamland] F.J. Davy (et al.), British Antarctic Survey, [http://www.antarctica.ac.uk/about_bas/publications/bas_bulletins/index.php BAS Bulletins 1963-1988]
			* [http://www.miem.gub.uy/portal/hgxpp001?5,8,90,O,S,0,PAG;CONC;91;1;D;2328;1;PAG;SRC;90;0;4879;N;SRC;MNU;E;21;2;MNU;, Bouguer anomaly map] depicting south-eastern [[Uruguay]]'s [[Laguna Merín\|Merín Lagoon]] anomaly (amplitude greater than +100 [[Gal (unit)\|mGal]]), and [http://www.miem.gub.uy/portal/hgxpp001?5,8,90,O,S,0,PAG;CONC;91;1;D;2329;1;PAG;SRC;90;0;4879;N;SRC;MNU;E;21;2;MNU;, detail of site].
			* [http://crustal.usgs.gov/projects/namad/state_listing.html List of Magnetic and Gravity Maps by State] by the [United States Geological Survey].


			[[Category:Geophysics]]
			[[Category:Gravimetry]]

en>InverseHypercube: /* References */ fixing link desc.

2012-05-20T20:31:17Z

References: fixing link desc.

New page

Introduction! I am Dalton. Acting is a thing that I appreciate totally addicted to. Vermont is literally where my home is certainly. Managing everyone has been my big day job for a even while but I plan at changing it. I've been toiling on my website during some time now. Visit it out here: http://prometeu.net<br><br>Also visit my page :: [http://prometeu.net clash of clans hack no survey download]

Second derivative test - Revision history

en>Walrus068: removed big tags

en>InverseHypercube: /* References */ fixing link desc.