Detection of damage to building side-walls in the 2011 Tohoku, Japan earthquake using high-resolution TerraSAR-X images

Building damage such as to side-walls or mid-story collapse is often overlooked in vertical optical images. Hence, in order to observe such building damage modes, high-resolution SAR images are introduced considering the side-looking nature of SAR. In the 2011 Tohoku, Japan, earthquake, a large number of buildings were collapsed or severely damaged due to repeated tsunamis. One of the important tsunami effects on buildings is that the damage is concentrated to their side-walls and lower stories. Thus this paper proposes the method to detect this kind damage from the change in layover areas in SAR intensity images. Multi-temporal TerraSAR-X images covering the Sendai-Shiogama Port were employed to detect building damage due to the tsunamis caused by the earthquake. The backscattering coefficients in layover areas of individual buildings were extracted and then, the average value in each layover area was calculated. The average value was seen to decrease in the post-event image due to the reduced backscatter from building side-walls. This example demonstrated the usefulness of high-resolution SAR intensity images to detect severe damage to building side-walls based on the changes of the backscattering coefficient in the layover areas.