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| | Abstract | | In theory, ground-penetrating radar (GPR) can detect the distribution of volumetric water content under the ground. However, the level of transition zone of water content in standard soil structures is difficult to be measured by using GPR. We evaluate time-shift analysis for time-lapse GPR records with different distribution of water content using FDTD numerical simulations. The reflection events from the transition zone of water content are sometimes difficult to detect on the survey sections of GPR also on the survey section subtracted from two time-lapse records. However, time-shift analysis can detect events caused by shift of the transition zone depth. Upper events of the transition zone move to in shallower travel time and lower events move to in deeper time when watertable moves to a shallower area. We discuss such characteristic phenomena in three analysis results applied for time-lapse records acquired in actual fields. Finally, we show methods to improve time-shift analysis using the result of opposite time differences and an initial modification record for the scanning direction. |
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