2.5-dimensional Numerical Simulation Software Developing Of Frequency Domain AEM

Airborne Electromagnetic (also is called AEM) is a commonly survey of airborne geophysical methods. Frequency domain helicopter-borne Electromagnetic System IMPULSE consists of two coils, known as horizontal Coplanar and Vertical coaxial. This article will carry out 2.5-dimensional forward study for the IMPULSE System and form a set of forward software. For he controlled source electromagnetic method, the underground electric parameters are two-dimensional, and the field source is three-dimensional, therefore the distribution of electromagnetic field is three-dimensional. So the 2.5-dimensional forward for the controlled source electromagnetic is three-dimensional forward. Since the electromagnetic field is symmetric to the center of source along the strike direction, we can convert the 2.5-dimensional space domain to the two-dimensional wave number domain through doing Fourier transform along the strike direction.Frequency domain helicopter-borne Electromagnetic has unique aspects relative to the ground electromagnetic:source with the magnetic source can be equivalent to the dipole, the receive parameter is the magnetic field, source and receive positions are a certain height above the ground, the offsets between source and receive is small and the offsets is fixed, source is moving and the frequency points is less. In the paper, we have performed the two-dimensional numerical simulation for the Frequency domain helicopter-borne Electromagnetic through the finite element method, and made study in source, boundary conditions, calculating the primary field with wave number domain, discrete wave number selection for inverse Fourier transform, the principles of generating the finite element mesh. Programmed a mesh division with the human-computer interactive software for the helicopter-borne electromagnetic, and developed a parallel algorithm for the AEM by using OpenMp parallel library to solve the low efficiency problem because of calculating the primary field with the wave number domain for each frequency to lay the foundation for the two-dimensional inversion. Also show the forward result andThis article also analyzed some typical two-dimensional model by using the new developed forward software. we understood the response characteristics under two coils. When the underground media is inclined plate body, prism body, the curve shows a bimodal device in horizontal coplanar with high frequency, the low frequency is single peak, but the curve shows a single peak in vertical coaxial with high frequency, the low frequency is bimodal. Then, the resistivity distribution both of the two coils has error, the horizontal coplanar showed large differences in the surface, but the vertical coaxial shows differences in the deep.