Page 245 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

227 at latitude func- a point, sta- the the of observation grav- in gravity center acceler- with m elevation. Earth’s mass the AR by function of M.

Anomalies acceleration with as viewed observation of (AR) center the the to change how the from gravitational (Ag) gravity elevation, AR): 6,367,000 = km increasing factors determining an observation point: a) latitude from sea-level datumto (AR): c) (M), relative to the station includes material above as level). @ is accounted for by subtracting the theoretical gravity observed gravity, and

Gravity gravitational increasing be can the of elevation to point local the considering by point the in change is, increasing - Fo - 6.367 = with Three 8.5 (&): b) distance observation point (M as below sea (free air anomaly)

that gradually surface (¢) latitude the 2) observation subsurface, relative effect, observation for equation the (that -2/GM)_ (FE) R and mGal/m gravity FIGURE gravity at distribution location well from the
estimates mGal, Earth’s the formula; the the second approximated of the the OM gives R, Earth - ee OR mGal in change Topography

it 90°). on 1) 8.5): from in the for be distance ees; to the _.(GM)_ (5) dk 980.625 —0.308 Level
8.4c), 978,037.85 = (@ location (Fig. gravity (R) (M) can Consider (R): respect of SS ~ the for Observation Point ee Sea
(Fig. be the poles specific theoretical radius distribution accounts deviation of increasing 8.6a). of radius with center the _dg_ aR ~ g of dg/dR value »

oblate spheroid would 0°) = at mGal Anomaly a at main components the by the changes mass the air correction elevation. That function (Fig. Earth function g, of from distance Ag _ KR Hm. values average = A R

an (@ Gravity observed of three for 3) The free to a as of the a as derivative average dg/dR
such equator 983,217.72 accounted which Earth: and due changes mass (g) first increasing Assuming (Fig. 8.4c):
For the to Air Gravity tion tion, point. ity of auion The where: ‘
Free

the gravity from
to in sub- a 1967 sphere, 8.4a).
the equator compared poles. c) Variation (observed gravity), yielding by point imperfect poles
pow = '6 then the of Geodesy: (Gal) (Fig.
'212'686
22

at the (theoretical gravity), approximated Association observation Gal) an is the
= 0°) acceleration 983.000 Gal at is + 0.000023462sin‘d) Earth through
Equator (¢ 9, = 978,031.85 mGal gravitational o latitude station r latitude International of the (978,031.85 (degrees). the that axis an

nce in station's the at given the latitude equator point fact about
m/s? difference the equator. to about a value a by 0.005278895sin* the the the rotating

Isostasy 9.83 = —> the Formula. for value actual for gravity adopted + for gravity at gravity observation account and

and g & 983,000 mGal for 978,000 mGal at Gravity gravity the from of Formula, (1 g of the into equator
Gravity a m/s? 9.78 = ; ASE factors responsible from about Reference 1967 the value anomaly. Gravity value Gravity = 2, theoretical = theoretical = latitude = takes the at

Chapter8 = g g b => mGal main a) Three predicting by that tracting gravity Theoretical average The Reference where: g, 2. ¢ equation The out bulging

978,000 8.4
226 poles. b) Gravity increases equator to pole, according to

ge FIGURE