Extreme Soil ‘Liquefaction’ Is Key Factor in Japan Earthquake Damage

Extreme soil liquefaction over hundreds of miles was responsible for much of the damage in Japan following the recent earthquake and tsunami, according to a new report. While it is common for major earthquakes to produce some liquefaction — a phenomenon in which soils lose their strength and act more like liquids, causing structures to shift or sink — the extent of soil shifting caused by the nearly five-minute earthquake on March 11 surprised even members of a Geotechnical Extreme Events Reconnaissance, or GEER, advance team that studied the recent earthquake. In a preliminary report, they say the duration of the recent temblor should make researchers reassess the threats of future earthquakes in regions such as the U.S. Pacific Northwest. “With such a long-lasting earthquake, we saw how structures that might have been OK after 30 seconds just continued to sink and tilt as the shaking continued for several more minutes,” said Scott Ashford, a professor of geotechnical engineering at Oregon State University and a member of the research team. According to the report, the shifting soil destroyed water, sewer, and gas pipelines, knocked out utilities and infrastructure, and caused some areas to sink as much as four feet.