The GPR uses microwave, since salt cannot absorb the microwave energy and which is an highly conductive it will lead to damage of the phones.

Hi Sir,

For any Electromagnetic method, medium must be resistive enough to travel the wave deeper. Salt, moisture or clay content make the medium conductive in which EM waves attenuate rapidly at very shallow depth.

If you are looking for voids/cavities, you can replace GPR with Multichannel Analysis of Surface Wave (MASW) survey and if you want to trace utilities, you can go for Magnetic Method. For hydrological investigation, you can do Electrical Resistivity Tomography (ERT).

Still I would suggest to do a test GPR survey on site with low frequency antenna.

Hello N. A. Karaki,

Generally, penetration depth of all EM signals or what is technically called skin depth in Physics, varies inversely as frequency. This implies the higher the frequency, the lower the penetration depth. Again, velocity of the signals decreases with resistivity of the medium. Therefore, formations dominated by low resistivity as is common in fine textured materials like clay, fine sands and in your case, salty materials, attenuation will be high and consequently, penetration will be low. In other words, poor subsurface model of such materials will be obtained with the GPR technique. However, by testing running the site using different antennae frequencies, an optimal antenna frequency can be obtained.

The depth of penetration is frequency dependent and it is predetermined by electrical resistivity or its converse, the conductivity of the formation. Depth of penetration is prevented by high conductivity and high energy loss factor and these factors are sensitive to skin depth that characterizes the EM signal sensed by the GPR. Therefore, in salt karst region, the conductivity is high and the resistivity is low. Since resistivity is inversely proportional to the frequency, region with high conductivity (salt) will be poorly penetrated as the conductive formation will not allow the current to penetrate deeply and this will be driven at higher frequencies.

If you are looking for utility detection, one more alternative survey can be done, is the Integration of Magnetic (Mag) and Radio Detection(RD) survey but both methods would response on underground metallic features only.

Thank you all for your very useful answers. Video on the Jordanian shore of the Dead Sea . Najib Abou Karaki