Do dams cause earthquakes in Japan?
Bad planning in the construction of dams in Japan makes the areas in which they are built more vulnerable to landslides and damage caused by earthquakes, argues environmental journalist Masano Atsuko. Tremors and volcanic eruptions are common on the Japanese archipelago and since much of the soil in certain regions is composed of tuff – a light, porous, rock formed from volcanic ash – mixed with other igneous rock, seismic activity can trigger landslides. In an article featured on the environmental news website China Dialogue, Masano Atsuko cites various instances in which the existence and/or construction of dams and reservoirs have apparently made several sites susceptible to landslides and may even cause earthquakes.
‘A few days after the earthquake, Tokyo University professor Konagai Kazuo appeared on NHK television’s Close-up Gendai special, “The Mountain that Disappeared: The Iwate-Miyagi Nairiku Earthquake”. He explained that, because ground water near the dam was high and snowmelt had permeated the ground, the violent shaking of the earthquake had caused the massive landslide.’
–Masano Atsuko, China Daily
The nature of tuff is that it is filled with crevices that collect water, making the rock prone to cave-ins. A case in point is the Aratozawa Dam, which experienced a major landslide three months after the Iwate-Miyagi Nairiku Earthquake occurred on northern Honshu, Japan’s principle island. Fallout from the quake included 13 deaths, 450 injured and 10 people unaccounted for as well as huge financial losses and extensive property damage.
Dams exacerbating the destructive power of earthquakes – and even ‘causing’ them – is not a phenomenon limited to Japan, according to Masano. It is believed that the Hoover Dam in the United States and India’s Koya Dam have contributed to similar occurrences. Other examples in Japan include 1984′s Nagano Seibu Earthquake and landslides at Magio Dam in Ōtaki, Chiba Prefecture. The Japanese government has continued to pursue other dam building projects, yet a footnote following another article by Masano Atsuko in the Asia Pacific Journal states: ‘The newly elected Democratic Party government announced a freeze on dam construction and canceled the Yamba dam in September, 2009′ partly for reasons given in the article. So it appears the new administration in Japan is considering the problem.
by Graham Land