Ground Deformation in the Kyoto Basin and Osaka Plain Detected with PS-InSAR
DPRI, Kyoto University, JAPAN
We have been conducting a persistent scatterer interferometry (PS-InSAR) of SAR images acquired by ALOS/PALSAR to reveal ground deformation and the configuration of basement of the Kyoto basin and the Osaka plain. We have analyzed PALSAR images from both ascending and descending orbits with the StaMPS software (e.g. Hooper et al., 2007) and applied a 2.5 dimension analysis to the interferograms.
We analyzed 20 SAR images from the path 414 (frame 680) acquired during the period from October 11, 2007 to October 19, 2010, and 15 images from the path 65 (frame2920) during the period from January 9, 2007 to October 20, 2010 to obtain LOS velocities of PS. Since this area is very urbanized, we found more than 1 million PSfs. There are several PSfs of significant LOS velocity.
We found differences in LOS change rates of up to 5cm/yr between both sides of the Uemachi fault that crosses from north to south in the Osaka plain. The LOS decrease dominates on the west side of the fault. This observation suggests that thickness of alluvium on the west side is larger than the east side. There are two traces of the Uemachi fault. The region of LOS decrease reaches the eastern trace of the fault.
We applied 2.5-dimension analysis to these interferograms to decompose LOS velocities in two directions into E-W and quasi-vertical components. Finally, we obtained uplift of about 1 cm/yr in the southern part of Kyoto basin and 5mm/yr subsidence along Arima – Takatsuki Tectonic Line, an ENE-WSW trending active fault zone. In these areas, we did not recognize notable horizontal components, which suggests that they are purely uplift or subsidence. It is noteworthy that the uplift in southern Kyoto is bounded by two active faults.
It is speculated that changes in groundwater table may affect the ground deformation in the Kyoto basin. The local government stopped pumping up groundwater in 2000. Therefore the recovery of groundwater table may have caused uplift. Subsidence along ATTL may also be related to change in groundwater level and associated compaction of soil.
PALSAR level 1.0 data were obtained from JAXA (Japan Aerospace Exploration Agency) under MEXTfs (Ministry of Education, Culture, Sports, and Science and Technology) research project gIntensive Observation of the Uemachi Faulth. The ownership of PALSAR data belongs to METI (Ministry of Economy, Trade and Industry) and JAXA.