Overview Regarding Geophysics

Top contributor | June 23, 2025

GEOPHYSICS

What is geophysics?

Geophysics is the scientific study of the Earth through measuring physical properties and applying physical laws.

As the name describes Geo means Earth, However the term geophysics is not only limited to the Earth but also can be applied to celestial bodies such as mars, moon, stars and even space.

This post is aiming to give you an overview regarding Geophysics.

The basic physical properties that are examined include magnetic, gravity, electrical conductivity, radiation and elastic properties.

Physical laws applied are the same as those of physics such as classical (Newtonian) and quantum (modern) mechanics. Example when gravity is measured, two (2) physical Newton laws are applied such as Newton's second law of motion (F=ma) and Newton universal law of gravitation (F=GMm/r2).

GEOPHYSICAL PROPERTIES

What are geophysical properties utilized in geophysics?

The physical properties are examined as the results of measure the respective physical parameters such as magnetic susceptibility, density, electrical conductivity, radiation, elastic parameter at which different geophysical methods such as,
Magnetic, gravity, electrical resistivity, Electromagnetic, Radiometric and seismic methods can be defined. See the table shown in figure (1).

The golden rule is that every geophysical method is related to each physical parameter. However to obtain the detectable results of the body of interest there must be physical contrast of that measured parameter with respect to the background value.

Example we know that the normal gravity value is 9.8m/s2, if we take measurement and 9.7m/s2 is observed, then the physical contrast for gravity is - 0.1m/s2. So physical contrast gives us the geophysical anomaly.

It means from the previous example the gravity anomaly is - 0.1m/s2, when the geophysical anomaly is positive indicates that there is an increase in magnitude of such physical parameter, while if it negative means there is decrease in magnitude of such physical parameter.

So the subsurface condition or structure of the body of interest including depth and quality can be revealed.

As it measures physical properties, the acquisition (collection) of geophysical data is done by using specialized instruments and sensors such as magnetometers (for magnetic survey), gravimeters (for gravity survey), radiation counters (for radiometric survey), geophones/hydrophones (for seismic surveys), and resistivity meters (for resistivity surveys).

TYPES OF GEOPHYSICAL METHODS

Geophysical methods can be implemented (applied) in two (2) ways as described here below,

1. Active Methods

These generate artificial signals and send them into the subsurface and measure the modified signals after being passed through it. Example seismic methods (refraction and reflection), electromagnetic method (EM) such as ground penetrating radar (GPR), electrical resistivity, induced polarization (IP) methods.

2. Passive Methods

These measure the natural fields of the Earth, they include self-potential (SP), gravity and magnetic methods.

BRANCHES OF GEOPHYSICS

Geophysics can be broadly grouped into two (2) branches

1. Theoretical (Pure) Geophysics

This deals with the theoretical concepts to understand the Earth processes, structures through the use of theory of physics. The main primary objective here is to gain an academic interest on the subject.

2. Applied Geophysics

It deals with the application of physical laws to the Earth to achieve an economic interest. Such as searching for mineral deposits, groundwater, energy resources like petroleum, coal, uranium deposits. Also in engineering projects such as civil, environmental, mining.

IMPORTANCE OF STUDYING GEOPHYSICS

Why do we study geophysics?

As described above most of importance of studying this subject is related to its primary interests

1. Academic interest

To get familiarized with Earth physical processes such as dynamics, structure, earthquakes, volcanic eruptions

2. Applied interest

To achieve an economic aim (goal) such as aiding in engineering projects, like site assessment, environmental contaminant remediation, mining designing. Also in extraction and searching of valuable Earth resources, for example petroleum (oil and gas), coal, uranium, groundwater and mineral resources.

In order to achieve the desired results the resolution of the sensors of the respective geophysical instruments is a important factor to be taken into consideration. However the sound knowledge of knowing which method and where it should be applied including its limitations also adds significant value.

Thank you for your attention!.

The table of relation between measured physical property (parameter) with appropriate geophysical method.