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

Quang Nguyen Hao,Satoshi Takewaka

doi:10.3390/rs13071399

Abstract

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

Highlights

The Great East Japan Earthquake, which occurred on 11 March 2011, with a magnitude of 9.0 on the Richter scale, was ranked among the five most powerful recorded earthquakes on Earth [1]
This paper has shown the effects of the 2011 Great East Japan Earthquake on shoreline change along the northern Ibaraki Coast, based on various satellite imagery sources (ASTER, ALOS AVNIR-2, and Sentinel 2)
Sudden retreats, ranging from 40 to 20 m, were observed along the coast significantly depending on the amount of initial subsidence

Summary

Introduction

The Great East Japan Earthquake, which occurred on 11 March 2011, with a magnitude of 9.0 on the Richter scale, was ranked among the five most powerful recorded earthquakes on Earth [1]. The horizontal movement to the east–southeast, land subsidence, and a tsunami have been observed after the earthquake in eastern Honshu, Japan. An inundation accompanying major land-subsidence caused by the earthquake and massive sediment transport caused by the tsunami resulted in a substantial loss of the coastal land in the eastern Honshu region [2,3]. (Tokyo Peil) data along the Ibaraki Coast, which is the area of interest of this study; the inundation height was approximately 19.5 m at the Sendai Plain in Miyagi Prefecture [4] (Figure 1). The rate of uplift along the northern Ibaraki Coast is different between the northern (+2.7 cm/year) and southern areas (+1.9 cm/year), based on the observed data from Global Navigation Satellite

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Discussion

Conclusion