Suchergebnisse

Abstract. Torrential rain triggered by two typhoons hit the Kanto and
Tohoku regions of Japan from 9 to 11 September 2015. Due to the record-breaking
amount of rainfall, several riverbanks were overflowed and destroyed,
causing floods over wide areas. The PALSAR-2 sensor on board the ALOS-2
satellite engaged in emergency observations of the affected areas during and
after the heavy rain. Two pre-event and three co-event PALSAR-2 images were
employed in this study to extract flooded areas in the city of Joso, Ibaraki
Prefecture. The backscattering coefficient of the river water was
investigated first using the PALSAR-2 intensity images and a land-cover map
with a 10 m resolution. The inundation areas were then extracted by setting
threshold values for backscattering from water surfaces in the three temporal
synthetic aperture radar (SAR) images. The extracted results were modified by
considering the land cover and a digital elevation model (DEM). Next, the
inundated built-up urban areas were extracted from the changes in SAR
backscattering. The results were finally compared with those from visual
inspections of airborne imagery by the Geospatial Information Authority of
Japan (GSI), and more than 85 % of the maximum inundation areas were
extracted successfully.

Abstract. The 2016 Kumamoto earthquake sequence was triggered by an Mw 6.2 event at 21:26 on 14 April. Approximately 28 h later, at 01:25 on 16 April, an Mw 7.0 event (the mainshock) followed. The epicenters of both events were located near the residential area of Mashiki and affected the region nearby. Due to very strong seismic ground motion, the earthquake produced extensive damage to buildings and infrastructure. In this paper, collapsed buildings were detected using a pair of digital surface models (DSMs), taken before and after the 16 April mainshock by airborne light detection and ranging (lidar) flights. Different methods were evaluated to identify collapsed buildings from the DSMs. The change in average elevation within a building footprint was found to be the most important factor. Finally, the distribution of collapsed buildings in the study area was presented, and the result was consistent with that of a building damage survey performed after the earthquake.

Abstract. The spatial distribution of the coseismic displacements that occurred along the Futagawa fault during the 2016 Kumamoto earthquake of Mw 7.0 was estimated using airborne light detection and ranging (lidar) data. In this study, a pair of digital surface models (DSMs) obtained from the high-density lidar data before and after the mainshock on 16 April 2016 were used. A window matching search approach based on the correlation coefficient between the two DSMs was used to estimate the geodetic displacement in the near-field region. The results showed good agreements with the geodetic displacements calculated from strong-motion acceleration records and coincided with the fault line surveyed by the Geological Survey of Japan.

Abstract. Lima, Peru's capital, has about 9.6 million inhabitants and keeps attracting more residents searching for a better life. Many citizens, without access to housing subsidies, live in informal housing and shack settlements. A typical social phenomenon in Lima is the sudden illegal occupation of areas for urban settlements. When such areas are unsafe against natural hazards, it is important to relocate such a population to avoid significant future losses. In this communication, we present an application of Sentinel-1 synthetic aperture radar (SAR) images to map the extension of a recent occupation of an area with unfavorable soil conditions against earthquakes.