Geophysics 101

Geophysics is the study of the physical properties of the Earth, especially its electrical, gravitational and magnetic fields. Geophysical data help us “see” underground, from a few meters to several kilometers, so we can draw conclusions about geological structures and processes. Geophysical surveys are safe, non-invasive, and cost effective at providing valuable data sets over a large area in a short period of time.

Geophysical data are used for a wide range of applications. The mining and oil and gas industries use geophysics to find mineral and oil and gas deposits, and to understand the subsurface rock layers and structures in which deposits are found. Engineers use geophysical data to analyze subsurface conditions prior to construction projects, and to identify geohazards that can impact infrastructure and human safety. Geophysical surveys can also be used to find and delineate aquifers/groundwater, and to map subsurface conditions at contaminated sites.

Geophysical data can be collected by three main methods - airborne surveys, ground-based surveys and marine surveys. Airborne surveys are typically used to obtain regional data sets for exploration purposes and provide an excellent “first look” at subsurface conditions within an area. Airborne geophysical surveys are performed with small airplanes or helicopters, whereby the geophysical instrumentation is fixed to the aircraft. This allows large areas to be surveyed quickly and efficiently compared to doing surveys on the ground.

Airborne surveys are usually designed with wide survey line spacing (i.e. 150-200 metres apart) and flown at an altitude of 100-200 metres above ground, depending on local circumstances. This provides comprehensive and detailed information over the survey area, while ensuring safety and minimal impact to the environment.

The real benefit of any geophysical data set is that it provides valuable information pertaining to conditions below the ground surface. Geologists and engineers can use geophysical data to increase the accuracy of their mapping and geological models, which optimizes any follow-up studies or investigations, such as mineral exploration. This improves quality and makes the overall project much more efficient, safe and successful.