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| | Abstract | | The 3DGPR, which provides high resolution time/depth slice images, has been used to determine the locations of the subsurface voids and infrastructure damages in Iwaki city, Fukushima, Japan. Two test sites have been investigated for high resolution subsurface imaging. These high-resolution 3DGPR subsurface images were obtained using 500 MHz and 100 MHz antennas. A 3D-fk migration of the three dimensional fused data on the basis of a constant velocity is performed. The 3-D migrated depth slice data was used for picking the buried objectives only for each individual slice. The extracted picks which represent the voids and underground water paths have been displayed in a 3D cube for better visualization and interpretation. Measurements that were carried out by using a 500 MHz antenna could detect two anomalous areas for land subsidence and damages in the infrastructures. The result of land subsidence anomalous areas was confirmed by drilling test wells, which could confirm the existence of three voids at 7m depth. Later a 100 MHz antenna was used in to image these deep voids, and we could validate the existence of voids at the depth of 7m. |
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