[STT50-05] Ups and downs in the Osaka metropolitan area, Japan, detected by LiCSBAS InSAR time-series analysis
Keywords:InSAR, Osaka Plain, Crustal Deformation
I processed 369 interferograms having formed from 128 Sentinel-1 SAR descending data (Frame ID: 017D_05514_131312, mean incidence angle 38.6 degrees looking from ESE) acquired between 23 November 2014 and 8 January 2020. The coherence was generally good in the urban areas, whereas the forest areas were automatically masked by the processor based on multiple criteria including coherence. The average LOS (line-of-sight) velocity in the area of interest (135/136/34.5/35.1) showed that the velocity fluctuation was within 10 mm/year (peak to trough) on most of the parts (Figure a). There are fluctuations of ups and downs (precisely, decrease and increase in the LOS displacements in a relative sense) in circular areas of typical diameter of 1-2 km. Since the time-series of displacements of all of these deformed areas exhibit clear secular trend and seasonal variations (Figure b), the signals probably reflect the real deformation. It was found that most of the subsiding areas (blue in the figures) was rice fields in the alluvial plain, possibly indicating the location of marsh areas before habitation (Figure c). Across the Arima-Takatsuki fault zone, a LOS velocity contrast of approximately 1.5 mm/year is observed across the fault (Figure d), but the sense of displacements is opposite to the long-term right-lateral displacements of the fault. Since the fault is located on the edge of a mountain region, there may be significant amount of atmospheric noise causing artifacts.
Acknowledgements: I am grateful to the European Space Agency for making Sentinel-1 data open, and Dr. Yu Morishita and his colleagues in the Centre for Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET) who contributed in developing the LiCSAR and LiCSBAS and made the code available online through https://github.com/yumorishita/LiCSBAS.