12:00 PM - 12:15 PM
[SGD01-06] Ground deformation in the Kyoto-Osaka-Kobe area and the Nara basin durin 2014 - 2021
Keywords:ground deformation, Sentinel-1, Kyoto-Osaka-Kobe area, InSAR time series analysis, Nara basin, ALOS-2
I processed SAR data during 1992 - 2010 and revealed ground deformation in the Kyoto basin and the Osaka plain (Hashimoto, 2014; Hashimoto, 2017). Among the detected deformations, the uplift is the southern Kyoto basin and the subsidence along the Arima-Takatsuki fault zone in the northern Osaka plain were the most remarkable. Hashimoto (2017) pointed out the latter might have been triggered by the 1995 Kobe earthquake. The termination of operation of ALOS-1 and Envisat after 2011 prevented us from tracking these deformations. Since 2014 when the Sentinel-1 and ALOS-2 were launched, however, we benefit a lot of abundant SAR images. In this report, I show the recent development of ground deformation in the Kyoto-Osaka-Kobe area and the Nara basin using these data.
I utilize unwrapped interferograms of Sentinel-1 opened in the LiCSAR site of the Leeds University (Lazecy et al., 2020) and perform time series analysis with LiCSBAS developed by Morishita et al. (2020). Tracks of images are T017D (descending) and T010A (ascending). I process images of P20-F2920 (beam U2-8 and U2-9) (descending) and P127-F680 (U2-6, scence shift -4) (ascending) of ALOS-2 with Gamma applying ionospheric correction. After unwrapping interferograms, I converted them to readable format of LiCSBAS to perform time series analysis. Finally, I convert average LOS velocities to quasi-EW and UD components.
I obtained the following results:
(1) Uplift became noticeable in the central part of the Osaka plain. Its peak is located in the middle of the cities of Osaka and Yao after 2018. Uplift was accelerated on the both sides of the Yodo river.
(2) Subsidence, which had been persistent since 1995, turned to uplift in the area between two active faults near the cities of Minoo and Takarazuka.
(3) Uplift became fast in area of the Koryo, Tawaramoto towns and the Tenri city in the southern Nara basin.
(4) Subsidence along the Arima-Takatsuki fault zone between the Takatsuki and Minoo cities, uplift in the area of the Ikoma and Nara cities are persistent. Subsidence of 10 mm/year or larger is going on in the southern Kyoto basin, especially in the Ogura reclaimed land, area along the Kizu river in the Yawata, Kyo-Tanabe and Kizugawa cities.
(5) Uplift of 10 mm/year or large that was detected by ALOS-1 in the southern Kyoto basin decelerated and its area shrank.
In 2018, they have suffered from several large disasters such as the Northern Osaka prefecture earthquake in June, the Western Japan torrential rain in July and the Typhoon Jebi (No.21) in September, which may have affected ground deformation. Shigemitsu et al. (2021) discussed the relationship with the earthquake. Taking a look at time series of LOS change, however, change in trend is found before the earthquake at some points and step-like change is seen after September at others. We recognize changes in the Nara basin in the similar period and consider not only earthquake but rainfall and structure may affect the deformation.
ALOS-2 images were provided by Japan Aerospace Exploration Agency under the following programs; JAXA 2nd Research Announcement on the Earth Observations (PI#: PI3052), Earthquake SAR Analysis Working Group of CCEP, GSI, and the Joint Reseach (B) "Study of crustal and ground deformation high frequent SAR observations" (Leader: Satoshi Okuyama) of the ERI Joint Usage/Research Program. Ownership and copyright belong to JAXA. Sentinel-1 interferograms are obtained from the LiCSAR site of the Comet project, the Leed University. I appreciate for these agencies and related personnels.
Figure. Average rate of ground deformation during 2018-2021. (a) Quasi-EW component. (b) Quasi-vertical component.
I utilize unwrapped interferograms of Sentinel-1 opened in the LiCSAR site of the Leeds University (Lazecy et al., 2020) and perform time series analysis with LiCSBAS developed by Morishita et al. (2020). Tracks of images are T017D (descending) and T010A (ascending). I process images of P20-F2920 (beam U2-8 and U2-9) (descending) and P127-F680 (U2-6, scence shift -4) (ascending) of ALOS-2 with Gamma applying ionospheric correction. After unwrapping interferograms, I converted them to readable format of LiCSBAS to perform time series analysis. Finally, I convert average LOS velocities to quasi-EW and UD components.
I obtained the following results:
(1) Uplift became noticeable in the central part of the Osaka plain. Its peak is located in the middle of the cities of Osaka and Yao after 2018. Uplift was accelerated on the both sides of the Yodo river.
(2) Subsidence, which had been persistent since 1995, turned to uplift in the area between two active faults near the cities of Minoo and Takarazuka.
(3) Uplift became fast in area of the Koryo, Tawaramoto towns and the Tenri city in the southern Nara basin.
(4) Subsidence along the Arima-Takatsuki fault zone between the Takatsuki and Minoo cities, uplift in the area of the Ikoma and Nara cities are persistent. Subsidence of 10 mm/year or larger is going on in the southern Kyoto basin, especially in the Ogura reclaimed land, area along the Kizu river in the Yawata, Kyo-Tanabe and Kizugawa cities.
(5) Uplift of 10 mm/year or large that was detected by ALOS-1 in the southern Kyoto basin decelerated and its area shrank.
In 2018, they have suffered from several large disasters such as the Northern Osaka prefecture earthquake in June, the Western Japan torrential rain in July and the Typhoon Jebi (No.21) in September, which may have affected ground deformation. Shigemitsu et al. (2021) discussed the relationship with the earthquake. Taking a look at time series of LOS change, however, change in trend is found before the earthquake at some points and step-like change is seen after September at others. We recognize changes in the Nara basin in the similar period and consider not only earthquake but rainfall and structure may affect the deformation.
ALOS-2 images were provided by Japan Aerospace Exploration Agency under the following programs; JAXA 2nd Research Announcement on the Earth Observations (PI#: PI3052), Earthquake SAR Analysis Working Group of CCEP, GSI, and the Joint Reseach (B) "Study of crustal and ground deformation high frequent SAR observations" (Leader: Satoshi Okuyama) of the ERI Joint Usage/Research Program. Ownership and copyright belong to JAXA. Sentinel-1 interferograms are obtained from the LiCSAR site of the Comet project, the Leed University. I appreciate for these agencies and related personnels.
Figure. Average rate of ground deformation during 2018-2021. (a) Quasi-EW component. (b) Quasi-vertical component.