Geophysics is a science that applied basic principles of physics in studying and exploring the subsurface of the earth. The aim of the geophysical
method is to estimate a model or subsurface object based on observational data. Survey methods in geophysical science consist of various kinds such
as geomagnetic surveys, geoelectrical surveys either 1D Geoelectrical surveys or Vertical Electrical Sounding (VES), and also 2D geoelectrical surveys
or electrical resistivity tomography (ERT), gravity surveys, georadar survey or ground penetrating radar (GPR), magnetotelluric (MT) survey, and similar
electromagnetic (EM) methods, Seismic Survey, all of which require hypotheses or estimates of the physical properties of objects subsurface which
contrasts with the physical properties of the surrounding medium/material.
Some of the popular physical properties include density or specific gravity in units of kg/cubic meter, susceptibility, the velocity of seismic wave
propagation in units of meters/second, and specific resistance or resistivity in units of ohms. , relative permittivity or dielectric constant, and
changeability. Recognizing the unique physical properties of the subsurface object that you want to know is the main thing that must be done so that
the application of the type or type of geophysical method can be applied correctly and properly. The character of subsurface objects is the main
determinant of the uniqueness of their physical properties. For example, igneous rocks are rocks resulting from magma freezing which will have a
character that has a high specific gravity compared to sedimentary rocks, and sedimentary rocks consisting of a variety of grain units will have
characters that have a high porosity compared to igneous rocks.
Before conducting a geophysical survey, several things need to be prepared including:
- The purpose of the geophysical survey.
- Information related to the survey area, such as topography, geology, and soil conditions.
- The geophysical method to be used and the parameters to be measured.
- The measuring instrument to be used and its technical specifications.
- Planning survey routes and distances between measurement points.
- Survey time and duration.
- Available budget and required costs.
- Occupational safety and health that must be complied with during the survey.
- Preparing a field team that has geophysical survey qualifications and experience.
- Permits and approval from the authorities if necessary.