Observation Results of the 2007 Noto Peninsular Earthquake by the Advanced Land Observing Satellite "Daichi"
At around 9:42 a.m. on March 25, 2007, Japan Standard Time (JST, all dates and times hereinafter are in JST,) a major earthquake, later named the "2007 Noto Peninsular Earthquake," hit the Noto region of Japan. The epicenter was offshore from the Noto Peninsular (about 40 km west-south-west of the city of Wajima.) The Japan Aerospace Exploration Agency (JAXA) detected a rise in the surface of the land due to the earthquake by analyzing observation images acquired by the Advanced Land Observing Satellite "Daichi" on April 10.Figure 1 shows the diastrophism by processing the image taken by one of the Daichi onboard sensors, the PALSAR*1, at 10:27 p.m. on April 10 and one also taken by the PALSAR on February 23, 2007, (Figure 2) using the differential interferometric method*2. The change of distance between the Daichi and the Earth in 47 days between Feb. 23 and April 10 is indicated by the two-dimensional colors in the image. We can observe a maximum of 45 centimeters of rise mainly in the western part of Monzen Town in the city of Wajima. The rises were concentrated within about a 40 km radius around the town. The Geographical Survey Institution of Japan also detected the diastrophism through GPS observations of a gap in a fault and other methods, and we were able to support their detection through data acquisition by the Daichi.
*1 PALSAR, Phased Array type L-band Synthetic Aperture Radar, is a microwave sensor receiving radio wave reflections transmitted from the satellite. It can acquire image data regardless of the weather and time of day.
*2 Differential interferometric process: Radars measure the distance to the Earth; therefore, we can find a rise or a cave-in caused by a subsidence of the land by the difference in distance between two observations.