The magnitude 8.8 earthquake that struck Chile on Saturday prompted the Japanese Meteorological Agency to issue "major tsunami" alerts. The quake killed more than 700 people in the South American country. Of the estimated 350 people who died in the seaside resort of Constitucion, it is thought many were killed by the impact of a tsunami.
In Japan, according to Kyodo News, evacuation orders were issued to some 522,000 people from nearly 200,000 households in 10 prefectures. Waves reaching heights of 20 cm to 120 cm hit various parts of the nation's Pacific coast. Although no deaths were reported, the aquaculture industry, especially in the Sanriku coast in the Tohoku region, suffered great damage. The experience is a strong reminder of Japan's tsunami vulnerability.
A tsunami, unlike ordinary waves, is not generated by the wind or tide. In an underwater earthquake, the ocean floor shifts upward or downward along a fault that might measure anything from several kilometers to several hundred. Water around the fault is displaced at speeds approaching that of a jet aircraft, building into a tsunami. The tsunami gradually slows as it nears land, but can be moving as quickly as 30 kph when it breaks the shoreline. If one has not evacuated by the time a tsunami comes into sight, it is too late.