Shoreline Changes along Northern Ibaraki Coast after the Great East Japan Earthquake of 2011

In this study, we analyze the influence of Great East Japan Earthquake, which occurred on 11 March 2011, shoreline northern Ibaraki Coast. After earthquake, area experienced subsidence approximately 0.4 m. Shoreline changes at eight sandy beaches along coast are estimated using various satellite images, including ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer), ALOS AVNIR-2 Land Observing Satellite, Advanced Visible Near-infrared Radiometer type 2), Sentinel-2 (a multispectral sensor). Before earthquake (for period 2001–January 2011), even though fluctuations in position were observed, shorelines quite stable, with averaged change rates range ±1.5 m/year. The suddenly retreated due to by 20–40 Generally, amount retreat shows a strong correlation land caused moderate tsunami run-up height. ground started uplift gradually after sudden subsidence, positions advanced accordingly. recovery speed varied from +2.6 m/year +6.6 m/year, depending beach conditions.