Page 247 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

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229 gravity center. in (M been look rela- deficiency; of because datum. tending mass infinite attrac- form of free

Anomalies the back Earth’s variations have Fig. 8.5) might anomalies shows anomaly mass station sea-level mass, extra the of an as mass 8.8b). The General gravity anomaly profile across areas of mass excess and mass deficiency.

Gravity puts (FAC) to (R) radius mass /ateral in AR and air the that the near features. to station the and have attraction the (Fig. station m. in 8.7 FIGURE

correction increased of (@ effects free changing Notice readings topographic from vary points would areas gravitational approximating the of elevation). kg/m*);h Datum Mass Deficiency

air function of mass. low sharp can observation the for by elevation 2npGh Constant 0.0419ph (10° / ! Level
free the for a is elevation excess, mimic mountainous done = (station yields: = g/cm?
the profile deficient mass the accounts is the BC slab 27 BC in p Air Anomaly i. Stations ae be Sea
adding correcting anomaly and a what and the that corrections, gravity lével, 8.8a). to slab Gravitational the and m/s?); ‘. Bec,

2) gravity latitude shows of excess near changes between sea (Fig. correction datum. This equal (h) Bouguer correction of the of G of (107° The Nagin,
Earth; and elevation, thereby air the 8.7 bodies readings abrupt Anomaly elevation mass near areas gravity Bouguer sea-level thickness is: slab density Universal thickness values the mGal in \ _-— Free ot i" Nao .

of the free The because 8.5), Fig. across high also are Gravity after in to the increase The the with a of such = BC p = G = h = Substituting is BC / 2"

bulge to lost Fig. corrected. like tively there Even differences Relative above slab, tion where: where e
Bouguer to /

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Center of Earth at than a station meters above h from Gal. readings stations observed latitude from and

. acceleration decreases by about 0.308 mGal point, elevated upward | about for the the (g,) spin the
Sl acceleration (g) observation feet) 10 by decreases gravity lower observations to back (m). datum for corrected station. gravity theoretical for accounting

(0.308 mGal/m) Datum lower gravitational a have radius to an (about m 3 every gravity to have therefore gravity compare added be must mGal/m) level sea a gravity, observed FAC + 8, the at observed the subtracting thus /atitude,

= h x ee Level from Earth’s surface, gravitational to tends extended the for that, due acceleration level sea To 8.6b). correction (0.308 X h (s72Gal) above the is - = anomaly acceleration 1) the for

Isostasy =—4R FAC Sea high elevation accounts for illustrates above (Fig. air free = FAC correction the station of anomaly Agy that: corrects

and Observation Point at (FAC) equation the Earth, high level a air station: gravity air gravitational equation (g)
Gravity Rising upward gravity station air correction above the of elevations sea near elevations, 8.6c). free elevation = h air gravity the of free = = g above the gravity

Chapter8 =Ri- Free air correction. a) meter of height. b) A free The surface the at Stations those than different with (Fig. values where: FAC = The free elevation and where: Ag,, in Notice observed the

228 ices AR * 980,625 mGal 6,367,000 m = dg/dR AQ/AR 8.6 lower elevation. c) The level datum.

a g, = R, = FIGURE for every a sea