BASE GEOPHYSICS

Self potential (SP) method is the one of passive form amongst electrical geophysical techniques. This is because self-potential signals originate naturally in the ground. This means that the SP signals are recorded with no need of applying electrical signals into the subsurface. The self- potential is generated itself within the Earth's ground due to various electrochemical processes such as electrical filtration , diffusion , adsorption and others as I will describe later in details. However the technique is based on a simple model where the generated natural ground potential difference (P.d) is measured in millivolts (mV) between two (2) points. Origin  (mechanism) of self - potential  1. Electrokinetic (Ek) potential Flowing of fluid (electrolyte) through a capillary or porous medium generates potentials along the flow path. The potentials are alternatively called electrofiltration , electromechanical or streaming potentials . The effect is believed to be due to electro...

Convolution is one among operations that is utilized in geophysical signal processing . However the term seems to not be clearly understood among us due to its formal similarity with other functions such as cross - correlation . Let's try to discuss in a simplified way through this post, how this term is really about in digital signal processing .  First of all, It would be a good approach in order to understand this term, we have to focus on a system that can feed (input) a certain variable and then produce the result as output variable. In digital signal processing, a linear system can change the signal feed into it and then give out another signal as output. The input signal can be decomposed into a set of impulses , each of which can be viewed as a scaled and shifted delta function , while the output signal resulting from each impulse is a scaled and shifted version of the impulse response . Then you see the overall output signal can be found by adding these scaled and shifte...

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 various " corrections " are described, and then the presentation options are listed. Just keep reading! Methods of gravity data reduction i/ Tidal and Drift corrections When drift and tidal correction is made, then correction 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 (gs) and at base station (gb) 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,...