GATE-2018 (24) :Wyllie – Time average equation

GATE-2007

 

11.Latitude correction applied gravity data reduction is maximum at the latitude of 

 

A) 0°                     B) 30°                  C)45°                        D) 60°

 

Solution:

 

Latitude Correction (g_n ) - Correction subtracted from “g_obs” that account for Earth's elliptical shape and rotation. The gravity value that would be observed if Earth were a perfect (no geologic or topographic complexities), rotating ellipsoid is referred to as the normal gravity.

 

Gravity increases with increasing latitude, correction is added as we move towards the equator.

 

Normal gravity formula or Theoretical gravity formula is,

g_n = 978031.85 (1 + 0.005278895 sin²(Φ) + 0.000023462 sin⁴(Φ)) mGal

 

Φ- latitude in degrees

Latitude correction is given below,

Δg_L= 0.000812 sin 2Φ mGal /m

 

Δg_L = 0.812 sin2Φ mGal / km

 

at latitude (Φ)= 45⁰

 

Δg_L= 0.812 *sin(2*45⁰) mGal/km                    sin90⁰=1

 

Δg_L =0.812 mGal/km 

 

 Therefore, at 45degrees latitude correction is maximum. 

Reference: http://epsc.wustl.edu/~epsc454/gravity/grav-corrections.pdf