Airborne Geophysical Services > Applications of Airborne Geophysics

Introduction

Airborne geophysical surveying is a process of measuring the variation of several key physical parameters of the earth. The most important parameters measured are magnetic susceptibility, density and radioactive element concentration. Any change in the earth's near surface that causes a measurable change in these parameters presents a potential application for airborne geophysics. The systems used to measure these parameters are magnetic, gravity and gamma-ray spectrometry.

Airborne magnetic surveys map the variation of the magnetic susceptibility, most often due to changes in the percentage of magnetite in the rock. Gamma-ray spectrometric surveys measure the radiation of one or more natural radioelements: potassium, uranium, or thorium, or a specific man-made radioelement. Gravity measures density contacts in the earth.

Anomaly Detection with Geophysics

The most obvious use of airborne geophysics is to directly detect internalization or directly measure the changes in the ground conditions of interest, by measuring the changes of one of the geophysical parameters relative to the surrounding "host" rock. It may have a stronger magnetic susceptibility or a density contrast, etc. However, there are many indirect ways geophysics can be applied to geological problems. The absence or reduction of a response can also be a direct indicator of geological targets.

Mapping with Geophysics

Regional variations in density, resistivity, susceptibility or radioelement composition measured by geophysics can all be used to map geology or geomorphology. Large areas can be flown at a relatively low cost compared to marine or ground surveys. Multiple sets of geophysical data can be combined with known geology to create regional geology maps and to develop priorities for follow-up on the most highly prospective ground.

Mapping geology with geophysics has the power to extend geological knowledge into areas where the geology is unknown.

Combining geophysical methods enhances the accuracy of the map(s) generated - they are more than the sum of the parts.

Case History, Ethiopia - Adola Area Mapping.