A study on the effect of sound velocity estimation for underground imaging

An efficient technique for detecting objects buried underground is expected for archaeological exploration and civil engineering. We have proposed a three dimensional underground imaging method by using an amplitude correlation synthesis processing and an electromagnetic induction type sound source. Because the sound velocity of sand and soil depends on a lot of physical parameters that varies with the area, it is needed to be measured before imaging processing. Up to now, the sound velocity employed for signal processing is measured by receivers buried underground near the area to be detected. In order to improve the efficiency of field detection, a method of estimating the underground sound velocity by the sound velocity measured from the ground surface is studied. In this study, the comparison experimental results of the velocity of underground transverse wave, the velocity of underground longitudinal wave, and the sound velocity measured from the ground surface are introduced. Furthermore, the effect on the image of underground objects brought forth by the sound velocity estimation is discussed.