BASE GEOPHYSICS

Concept of Gravity Anomaly  Gravity anomaly can be defined as the differences  between the corrected measured gravity and the theoretical (normal) gravity. In most cases gravity anomaly reading is given in milliGal (mGal). As the definition above describes, there are two terms you must understand related to the gravity anomaly such that normal gravity and the observed gravity . Then these terms are described here below in order to get basic insight on this topic. - Normal (theoretical) gravity This is the value of gravity computed without any geological complication. It is computed by the normal gravity formula of the Geodetic reference system. - Observed gravity This is the gravity reading observed at each gravity station after correction have been made for drift and tides. Factors affecting gravity anomaly - Dimensions When we are talking about the dimension of a body we simply mean the size. As the size of the body increases, the probability of producing great gravity att...

When conducting gravity surveying effects caused by predictable features that are not part of the " geophysical target ." should be removed while the remaining anomaly is then interpreted in terms of sub-surface variations in density. Each known effect is removed from observed data. This is commonly known as Gravity Data Reduction, which I want you to understand its basic concepts. First the various " corrections " are described, and then the presentation options are listed. Keep enjoying your reading! Methods of gravity data reduction i/ Tidal and Drift corrections When Drift and tidal correction is made, it is given as  ∆g = g s - g b  Where drift corrected gravity anomaly (∆g) is given as the difference in gravity measured at survey point and at base station at the same time. Procedures - Establish the location of one or more gravity base stations - Establish the locations of gravity stations. - Reading relative gravity at the base station and time, then procee...

When it comes to the issue of how to measure the magnitude of  acceleration due to gravity (g), it leaves some gaps among others. Okay! Today I want to let you know through this post the basic concept on how this gravity is measured. Keep reading.!  There are common two (2) methods that are frequently utilized in measuring acceleration due to gravity in geophysics. How can you measure gravity? 1: Absolute gravity Method This method  involves measuring gravity at only one point. This method gives true gravity. i/ Pendulum Method When it comes to simple Pendulum, it consists of a string which is attached to a small mass metal object known as Pendulum Bob. This system is displaced at a small angle less than 15° and allowed to move freely in a simple harmonic motion provided that the effect due to air resistance is neglected see Figure 1 below.  Figure 1: Simple Pendulum and its resolved forces. When the Pendulum execute Simple Harmonic Motion (S.H.M), force components b...