Crosshole radio-frequency (typically from 1 to 36 MHz) electromagnetic methods are powerful tools for locating conductive ores, caves and structures buried between boreholes (or tunnels) or borehole (or tunnel) and earth's surface.
In the range of these frequencies, electromagnetic field can be approximated by the wave field. Usually, crosshole radio-frequency electromagnetic inversion requires exact source intensity but it is difficult to determine that.
We present a ray-based inversion method of crosshole radio electromagnetic data which does not require exact source intensity.
We have introduced the conception of apparent source intensity of antenna and established the method of determining it and realized absorption and conductivity tomographic inversion of crosshole radio electromagnetic data using it.
Using positive constraints for conductivity and absorption we have enhanced the accuracy and reliability of the inversion and applied adaptive control gradient method as the method of inversion.
The method we proposed has little differences in determining absorptions and conductivities of host rocks, but can compare to that using exact source intensity in determining absorptions and conductivities of targets.
Model experiment and field test show that our method can be fairly applied to interpretation of crosshole radio electromagnetic data.
This result was published in the "Journal of Applied Geophysics"(2023) under the title of "Crosshole radio electormagnetic tomography using apparent source intensity and logarithmic barrier"(https://doi.org/10.1016/j.jappgeo.2023.104987).
