Electromagnetic parameters of rocks in short wave band (mainly 15 MHz), such as resistivity and dielectric constant, were examined for various rocks and minerals to derive a proper geological interpretation from radar tomographic data.
In this paper, influences of lithologic characters, for example, mineral or rock type, porosity, grain diameter, were tested in detail.
Obtained results are as follows:
1. Resistivity and dielectric constant decrease as the increase of frequency. The decrease rate of resistivity of dried rock is higher than that of saturated rock, and the decrease rate of dielectric constant is inverse to that of resistivity.
2. Resistivities of minerals are distributed in proportion to the-2--3 power of dielectric constants of those minerals.
3. Minerals can be classified four types on the diagram of resistivity versus dielectric constant, felsic minerals, mafic minerals, clay minerals, and iron ore, in order from high resistivity and low dielectric constant to low resistivity and high dielectric constant.
4. Resistivities of part of sedimentary rocks and volcanic rocks are relatively lower than those of minerals which have the same dielectric constant.
5. Dielectric constant of dried rock is approximated to the Lichtenecker's law.
ε: relative dielectric constant of a dried rock, a-n: volume rate of each minerals or pore, here a+b+…+n=1, εa-εn: relative dielectric constant of each minerals and pore air.
6. In the case of dried rock, the resistivity increases in proportion to the -2--3 power of the dielectric constant according to the increase of porosity. In the case of saturated rock, dielectric constant continuously increases according to the increase of porosity, but the resistivity mostly decreases at a specific porosity.
7. The resistivity of a rock decreases according to the reduction of its grain diameter.
Some of these results are correspond to the past studies qualitatively except for the result No.2. 4. and 6. which are unknown in the past.
