The 2011 Tohoku-Oki (Japan) tsunami inundation and liquefaction investigated through optical, thermal and SAR data

Abstract

We studied the disastrous effects of the tsunami triggered by the Mw 9.0 earthquake that occurred on 11 March 2011 offshore the Honshu island (Japan). The tsunami caused a huge amount of casualties and severe damage along most of the eastern coastline of the island. The dataset used is composed of images from ASTER (visible and thermal) and ENVISAT SAR sensors. The processing and the analysis of data from different sources were performed in order to obtain the tsunami inundation map of the Sendai coastal area, to analyze inland factors driving the tsunami inundation, and to detect the liquefaction effects in the Chiba bay area as well. The obtained inundation line, with a maximum value of about 6 km, has been jointly analyzed with DEM providing the run-up values, which are generally below 21 m in the ca. 60-km-long study area of Sendai. The analysis highlights that the coastal topography influences the inundation process: high-relief zones record the lowest inundation distances, while within the plain the waves entered inland for at least 4 km. We did not observe significant direct effects of the vegetation cover on the inland water penetration along the whole investigated area, nor of the different orientation of the coastline. Moreover, from SAR coherence and intensity correlation a wide area of subsidence is mapped at Chiba bay, which is reasonably related to strong ground shaking and pervasive liquefaction.