Page 252 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

function of the pendulum’s Jength
235
Gravity
of
Measurement
is a
T=0 Te
a) Measurement of absolute 8.14 FIGURE Drop Weight Perndulum b) gravily.a) Weight drop. The object velocity of V, initial an accelerates from = (T time at at velocity of V, 0), to a (z). distance falls a 1), as it = (T time Pendulum. Gravitational b) acceleration Sie of oscillation (L) and period (T). = V; V saee frnenemreld.. Gravity Absolute absolute measure to ways basic two

rela- object gravita- (g). acceleration to

and an in a) Absolute gravity is acceleration (g,) compared
absolute of Relative gravity reflects the gravitational station
+2.67) —1.64) in acceleration difference 8.13 truc gravitational in one

= = the FIGURE difference another (g,).
p (for (7Ga/) p (for (77Gal) (m). (17Gal) measured is the b) (Ag) at

(m). BC 0.0419ph anomaly (m). datum h, | sea al point TC + anomaly cas be can the actual] gravity another.
datum — Ag, — Ag, (mGal) (g/cm?) mGal/m)h | mGal/m) anomaly observation Agy = gravity (71Gal). surface reflects relative to

(Gal) (Gal) Jevel = (0.112 gravity sea-level below Agne Earth’s gravity while compared
Isostasy gravity sea Ag, correction density — Bouguer above (0.0687 gravity depth Bouguer correction GRAVITY on surface, station

and gravity above Gravity Anomaly Bouguer reduction Ag, elevation Ag, + Bouguer Terrain: complete Absolute Earth’s one
Gravity observed theoretical elevation = = Land = Ag, simple = = Sea = I = water h,, = Rugged = = terrain OF acceleration 8.13). at

= = = BC p On Ag, h b) At Ag,, Ag,, In Ags, TC (Fig. toward acceleration Gravity Gravity
g g, h Bouguer a) c)
Chapter 8 MEASUREMENT Gravitational senses tive falls it as tional G9

234 Absolute Relative
a) b) g