Earlier this month, Japanese scientists warned that the Fukushima Daiichi nuclear station was at a greater risk from future earthquakes than previously estimated. The March 11th earthquake was the most powerful known earthquake ever to have hit Japan, and one of the five most powerful earthquakes in the world since modern record-keeping began in 1900.
The huge scale of the Great East Japan Earthquake has resulted in forcing the Japanese government to review the basic principles of its earthquake risk assessment system and may have far-reaching consequences for anti-quake measures in homes, offices and nuclear power plants across the country.
A group of Japanese scientists and prefectural officials by University of Tokyo Professor Shinji Sato have found that a tsunami more than 21 meters high hit the coast near the Fukushima Daiichi nuclear plant on March 11th last year. Prior to these findings, many experts had held the opinion that the tsunami waves were less than 10 meters high in many spots.
This is the first study of tsunami in the area since last year’s earthquake as no one was allowed to enter the zones due to radiation from the plant. Sato said it is necessary to study why the tsunami were so high in the area around the plant, as this will help in drawing up preventive measures.
The tsunami brought destruction along the Pacific coastline of Japan’s northern islands and resulted in the loss of thousands of lives and devastated entire towns. The shape of the coastlines along Kamaishi Bay, Ishinomaki Bay and four other areas in Tohoku may have amplified the power of the tsunami that struck there last March.
The tsunami walls at several of the affected cities were based on much smaller tsunami heights. A joint research team from Yokohama National University and the University of Tokyo also reported that the tsunami at Ryōri Ōfunato was about 30 m high. They found fishing equipment scattered on the high cliff above the bay.
The tsunami caused by the 2011 off the Pacific coast of Tohoku Earthquake on 11th March 2011 inflicted massive damage to the tsunami and tide level observation stations in the Pacific coast of Tohoku region and northern part of Kanto region (Aomori, Iwate, Miyagi Fukushima and Ibaraki Prefectures). For comparison, on March 23rd 2011, the Port and Airport Research Institute reported their estimated tsunami height by at various sites from offshore observations as follows:
- Port of Hachinohe area – 8–9 m (26–29 ft)
- Port of Kuji – 8–9 m (26–29 ft)
- Mooring GPS wave height meter at offshore of central Iwate (Miyako) – 6 m (20 ft)
- Port of Kamaishi – 7–9 m (23–30 ft)
- Mooring GPS wave height meter at offshore of southern Iwate (Kamaishi) – 6.5 m (22 ft)
- Port of Ōfunato – 9.5 m (31 ft)
- Run up height, port of Ōfunato area – 24 m (79 ft)
- Mooring GPS wave height meter at offshore of northern Miyagi – 5.6 m (18 ft)
- Fishery port of Onagawa – 15 m (50 ft)
- Port of Ishinomaki – 5 m (16 ft)
- Mooring GPS wave height meter at offshore of central Miyagi – could not measure
- Shiogama section of Shiogama–Sendai port – 4 m (13 ft)
- Sendai section of Shiogama-Sendai port – 8 m (26 ft)
- Sendai Airport area – 12 m (39 ft)