Melted snow permeating the soil of a mountain was likely the cause of a landslide in northeastern Japan last week that left two dead, according to an expert who conducted an on-site probe.
Hiroshi Yagi, professor emeritus of geomorphology at Yamagata University, also called Thursday for caution about lifting evacuation orders for residents of Tsuruoka in Yamagata Prefecture, citing the risk of further disasters given the snowfall in December.
The survey, joined by prefectural and municipal governments, confirmed that subsoil on the mountain has weathered and loosened over time, making it easily collapsible, according to Yagi, adding that the risk of landslides will increase when snow melts.
The city has issued evacuation orders to 20 people in seven households near the affected zone, but Yagi, who is also a former president of the Japan Landslide Society, said a full-scale investigation spanning several months is necessary to confirm the safety of the area.
"Vigilance is needed until the snow melts in early spring," said Yagi. "Without taking time to investigate, it is difficult to tell people that they can return home with a feeling of assurance."
About 10 buildings were destroyed or damaged when landslide occurred at around dawn on New Year's Eve, killing a man in his 80s and his wife in her 70s.
The landslide measured 20 to 30 meters in height, 100 meters in width and moved about 20,000 cubic meters of sediment, local authorities said.
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