EXTRACTION OF FLOODED AREAS DUE THE 2015 KANTO-TOHOKU HEAVY RAINFALL IN JAPAN USING PALSAR-2 IMAGES

Informal occupation of unused lands for settlements is a critical issue in Peru. In most cases, such areas are unsafe against natural hazards. We performed a time-series analysis of Sentinel-1 images at recent informal settlements in Lima. The result suggests that a low-cost and sustainable monitoring system of informal settlements can be implemented.

Five synthetic aperture radar images are employed to monitor the changes in the inundation areas caused by torrential rain from 9 to 11 September 2015, in the city of Joso, Ibaraki Prefecture, Japan. The inundation areas were then extracted by setting threshold values for backscattering intensity. The results were modified by considering the land cover and a digital elevation model. Compared with the results from visual inspections, 85 % of the inundation area could be extracted successfully.

On 14 April 2016, an M_w 6.5 earthquake occurred in Kumamoto prefecture, Japan (foreshock). About 28 h later, another earthquake of M_w 7.0 occurred (mainshock). The earthquake produced extensive losses to the infrastructure. This paper shows the extraction of collapsed buildings from a pair of airborne lidar data recorded before and after the mainshock. A number of methods were applied and their performances were evaluated by comparison with actual data obtained from a field survey.

This paper calculates the coseismic displacement produced during the 16 April 2016 M_w 7.0 Kumamoto earthquake from a pair of digital surface models (DSMs), acquired before and after the earthquake from airborne lidar data. A window matching search approach based on the correlation coefficient was used for this purpose. Results are consistent with the coseismic displacement estimated from strong-motion acceleration records and with the surveyed surface rupture.

The method for capturing two-dimensional surface displacements was applied to three pairs of pre- and post-event high-resolution TerraSAR-X intensity images of the 2011 Tohoku-Oki earthquake taken in ascending and descending paths, and the results were used for estimating the actual three-dimensional movements. Compared with the GPS data at three ground-control stations, the estimation errors in the horizontal and vertical directions were less than 0.3 m in spite of the pixels size (1.25 m).