Characterization of fracture surface by polarimetric borehole radar

Borehole radars have successfully been applied to various fields such as geological survey, geophysical exploration and subsurface crack measurement. However, only single polarization measurement has been performed in conventional single-hole borehole radar measurement because dipole antennas which radiate an electric field parallel to borehole axis are usually used. Radar polarimetry is a promising technique to extract more information such as size, shape, orientation or surface condition of radar targets in borehole radar measurement. We developed a system which uses an axially oriented slot antenna on a conducting thin cylinder which radiates an electric field perpendicular to the borehole axis in order to obtain the polarimetric information. We also developed a method to compensate the characteristics in each antenna which gives a target scattering matrix. We present the result of application of the polarimetric borehole radar measurement to characterization of surface roughness.