EFFECTIVE TSUNAMI PROTECTION IN JAPAN - REVIEW AND DISCUSSION OF NEEDED MEASURES.

The 11 March 2011 Tohoku earthquake and tsunami, also known as the Great Sendai severe disaster and as the "Heisei" tsunami, occurred off the northeastern coast of Japan's main Island of Honshu, resulting in extensive destruction and the death of 22,000 people. Also, tsunami waves struck the Fukushima nuclear power plant on the coast, thus setting in motion a major accident and spreading long-lasting radioactive material in the ocean, with farreaching impact on marine life in the North-West Pacific Ocean. Besides the large magnitude of the destructive earthquake, the main factors responsible for the great loss of life was due to the fact that existing tsunami protective countermeasures, such as seawalls, were inadequate in providing protection given the extreme height of the 2011 tsunami waves. The seawall was overtopped by these waves and large sections were destroyed by the accompanying debris flow, thus reaching further into the harbor. Subsequently, waves traveling up the river, transformed into a river-type of tsunami, overtopping river embankments, flooding the surrounding areas, and causing great loss of life and destruction, as in the past 115 years caused by great magnitude earthquakes and destructive tsunami events. These were: 1) The magnitude Mw=8.5 tsunami generating Meiji Sanriku earthquake of 15 June 1896 in Japan; 2) The magnitude Mw=8.4 tsunami generating Showa Sanriku earthquake of 3 March 1933 in Japan; 3) The magnitude Mw= Mw=7.7 Hokkaido Nansei-Oki tsunami generating earthquake of 12 July 1993; and 4) The magnitude Mw=9.4-9 Valdivia-Chile earthquake and tsunami of 22 May1960. The present study examines Japan's government countermeasures in providing effective tsunami predictive and protection measures from such extreme and catastrophic tsunami recurrences in the future, and particularly against the threat of river tsunamis. [ABSTRACT FROM AUTHOR]