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ALOS/PALSAR Observation Results of the Magnitude-9.0 Earthquake off the Pacific coast of Tohoku-Kanto District in Japan in 2011 (3)

On March 11, 2011 (UTC), a magnitude 9.0 huge earthquake occurred off the Pacific coast of Tohoku-Kanto district of Japan (38.32°N, 142.37°E, 32 km in depth; hypocenter information from USGS Web site), accompanied by a massive tsunami. The earthquake and tsunami caused severe damage in many cities, and more than 20 thousand people were killed and lost their homes. The Japan Aerospace Exploration Agency (JAXA) has performed emergency observations since the occurrence of the earthquake, using the Phased Array type L-band Synthetic Aperture Radar (PALSAR) installed on the Advanced Land Observing Satellite (ALOS, "Daichi"). In this report, we conduct differential interferometric SAR (DInSAR) processing to detect crustal deformation associated with the earthquake using PALSAR data acquired before and after the earthquake.

The blue and light-blue rectangles indicate the observation area shown in Fig. 2. The red star represents the epicenter of this earthquake.
Fig.1: An overall view of the observation area (We refer to SRTM3 as terrain data)
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Figure 2 left shows two tracks of interferograms (path: 402 and 405) generated from PALSAR data acquired before and after the earthquake using the DInSAR technique. A color pattern illustrates changes of satellite-ground distance for the period (402: 2010/9/29-2011/4/1, 405: 2011/2/19-2011/4/6). Figure 2 right shows two tracks of PALSAR amplitude images acquired after the earthquake. In Fig. 2-left, there are so many color fringes over the whole area in the images, and we can count at least 34 cycles of fringes. We interpret that ground movements away from the satellite at the tip of Ojika Peninsula are about 4m. Considering a mechanism of this earthquake, the color pattern indicates a subsidence or eastward displacement in the area.
Fig.2: PALSAR interferograms indicating crustal deformation
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Fig.2: PALSAR amplitude images observed after the earthquake
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JAXA plans to continue ALOS observations of the afflicted area.

The color changes from blue to red, yellow, green, and back to blue indicate an extension (and an opposite pattern indicates a shortening) of the satellite-ground distance. One color cycle is equal to 11.8 cm.
Fig.3: Mosaicked PALSAR interferogram (ascending orbits) showing deformation map.
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