Tsunami Heights along the Pacific Coast of Northern Honshu Recorded from the 2011 Tohoku and Previous Great Earthquakes

Abstract

The 2011 Tohoku earthquake generated a huge, destructive tsunami with coastal heights of up to 40 m recorded along northern Honshu. The Sanriku coast experienced similar tsunamis and damage from the 1896 and 1933 Sanriku earthquakes, whereas the only damaging tsunamis on both the Ibaraki and Chiba coasts in the previous century were from the 1960 and 2010 Chile earthquakes. We summarized 12 field surveys in which the height of the 2011 tsunami was recorded at 296 points, along with descriptions of the survey method, reliability, and accuracy. We then compared them with the above-mentioned tsunamis at locations for which specific measurements were given in previous reports. On the Sanriku coast, the 2011 tsunami heights are positively correlated with the previous Sanriku tsunamis, indicating that local variations resulting from the irregular coastline were more dominant factors than the earthquake location, type, or magnitude for near-field tsunamis. The correlations with the Chilean tsunami heights are less significant due to the differences between the local and trans-Pacific tsunamis. On the Ibaraki and Chiba coasts, the 2011 Tohoku and the two Chilean tsunami heights are positively correlated, showing the general decrease toward the south with small local variations such as large heights near peninsulas.