Keywords:

Abstract:

A versatile discrete conductor model is used to generate the maximum signal-to-noise ratio along an airborne electromagnetic (AEM) profile. By varying the depth and lateral offset of the conductor, a footprint section can be generated that shows how material below the ground surface responds to the AEM system. This type of footprint accounts for the coupling of the transmitter to the model and the induced current flow to the receiver. The model we use can also account for variable orientation of the current flow. The sensitivity of an AEM system to a conductor depends strongly on the receiver component measured and the orientation of the current flow in the conductor. In general, a z-component receiver is better for seeing to depth and the y component for seeing conductors to the side. The x component is best for seeing conductors where the currents are constrained to flow vertically and per pendicular to the flight direction of the AEM system. The footprint sections can also be used to estimate the optimal spacing between airborne traverses: in order to ensure effective exploration down to 300 m and not miss a conductor between lines requires that helicopter EM systems fly with a flight line spacing of 200 m whereas the more powerful fixed-wing AEM systems can obtain equivalent coverage by flying lines spaced 380 m apart. Our model could also be used to estimate the size of the footprint in "moving footprint" 3D inversion schemes.

Notes:

GeoRef, Copyright 2018, American Geological Institute.<br/>2014-017276<br/>discrete conductor model<br/>electromagnetic profiles<br/>footprint sections<br/>moving footprint