What Is Geophysics?

Geophysics is: The field of natural science aimed with the physical processes and physical properties of the earth and it’s surrounding and the use of quantitative methods for their analysis. . In other word, it is the non-invasive investigation of subsurface conditions in the Earth through measuring, analyzing and interpreting physical fields at the surface.

However, geophysics was only recognized as a separate discipline in the 19th century, its origins date back to ancient times. The first magnetic compasses were made from lodestones, while more modern magnetic compasses played an important role in the history of navigation. The first seismic instrument was built in 132 AD. Isaac Newton applied his theory of mechanics to the tides and the precession of the equinox; and instruments were developed to measure the Earth’s shape, density and gravity field, as well as the components of the water cycle. In the 20th century, geophysical methods were developed for remote exploration of the solid Earth and the ocean, and geophysics played an essential role in the development of the theory of plate tectonics.

Physical phenomena: Although geophysicists contribute to every area of the Earth sciences and Geophysics is a highly interdisciplinary subject. Depending on the problem under study, one has to decide which method should be applied. e.g. for ground water surveys, Electrical method is helpful. For mineral deposits, one can adopt Gravity and/or Magnetic surveys. For Oil & Natural Gas, one has to carry out Gravity, Magnetic surveys to get rough idea about structure of rock formations. If the desired structure is existing, for detailed study of rock formations, one has to carry out Seismic and/or Magneto-telluric surveys.

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Gravity: Which means the force a attraction that exist between two masses. The gravitational pull of the Moon and Sun give rise to two high tides and two low tides every lunar day, or every 24 hours and 50 minutes. Therefore, there is a gap of 12 hours and 25 minutes between every high tide and between every low tide.

Benefits of Geophysics:

1. Many Geophysics are non-destructive to populated area such as; cities, where many of today’s environmental and engineering issues arise. It also means an archeological site can be examined without destroying it in the process.
2. Efficiency is possible because it provides a means of evaluating large areas of the subsurface rapidly.
3. Geophysical measurement assesses the characteristics of soil and rock at very small strains, typically on the order of 0.001 percent thus providing information on truly elastic properties.
4. In general, cost-effective does not require excavation or direct access to subsurface (except in the case of borehole methods where access is typically by drilled holes). This means vast volumes of earth can be evaluated at far less cost than excavation or even grid-drilling methods.

Limitations of Geophysical:

1. Most methods work best for situations in which there is a large difference in stiffness between adjacent subsurface units.
2. Gravity
3. Results are generally interpreted qualitatively and therefore useful results can only be obtained by an experienced engineer or geologist familiar with the particular testing method.
4. Specialized equipment is required (compared to more conventional subsurface exploration tools).