"Liquefaction" Key to Much of Japanese Earthquake Damage
The massive subduction zone1 earthquake in Japan caused a significant level of soil "liquefaction"2 that has surprised researchers with its 1 severity, a new analysis shows.
　　"We’ve seen localized3 examples of soil liquefaction as extreme as this before, but the distance and 2 of damage in Japan were unusually severe," said Scott Ashford, a professor of geotechnical engineering4 at Oregon State University5. "Entire structures were tilted and sinking into the sediments," Ashford said. "The shifts in soil destroyed water, drain and gas pipelines6, crippling the utilities and infrastructure these communities need to 3 . We saw some places that sank as much as four feet."
　　Some degree of soil liquefaction7 is common in almost any major earthquake. It’s a phenomenon in which soils soaked with water, particularly recent sediments or sand, can lose much of their 4 and flow during an earthquake. This can allow structures to shift or sink or 5 .
　　But most earthquakes are much 6 than the recent event in Japan, Ashford said. The length of the Japanese earthquake, as much as five minutes, may force researchers to reconsider the extent of liquefaction damage possibly occurring in situations such as this8.
　　"With such a long-lasting earthquake, we saw 7 structures that might have been okay after 30 seconds just continued to sink and tilt as the shaking continued for several more minutes," he said. "And it was clear that younger sediments, and especially areas built on 8 filled ground, are much more vulnerable."
　　The data provided by analyzing the Japanese earthquake, researchers said, should make it possible to improve the understanding of this soil 9 and better prepare for it in the future. Ashford said it was critical for the team to collect the information quickly, 10 damage was removed in the recovery efforts9.
　　"There’s no doubt that we’ll learn things from what happened in Japan10 that11 will help us to reduce risks in other similar 11 ," Ashford said. "Future construction in some places may make more use of techniques known to reduce liquefaction, such as better compaction to make soils dense, or use of reinforcing stone columns."
　　Ashford pointed out that northern California have younger soils vulnerable to liquefaction ---on the coast, near river deposits or in areas with filled ground. The "young" sediments, in geologic terms, may be those 12 within the past 10,000 years or more. In Oregon, for instance, that describes much of downtown Portland, the Portland International Airport and other cities.
　　Anything 13 a river and old flood plains is a suspect12, and the Oregon Department of Transportation has already concluded that 1,100 bridges in the state are at risk from an earthquake. Fewer than 15 percent of them have been reinforced to 14 collapse. Japan has suffered tremendous losses in the March 11 earthquake, but Japanese construction 15 helped prevent many buildings from collapse ---even as they tilted and sank into the ground.
　　詞匯：
　　subduction n.俯沖
　　sediment n.沉積;沉淀物
　　liquefaction n.液化
　　infrastructure n.基礎(chǔ)設(shè)施
　　geotecnical adj.巖土技術(shù)
　　compaction n.壓緊的
　　vulnerable ad].易受傷害的
　　注釋：
　　1. subduction zone：俯沖帶。亦稱下降帶、潛沒帶、消亡帶。板塊構(gòu)造說認(rèn)為，當(dāng)大洋板塊移動(dòng)并與大陸板塊相遇時(shí)，由于大洋板塊巖石密度較大，地位也低，便俯沖到大陸板塊之下，這一俯沖部分叫做俯沖帶。俯沖帶兩側(cè)板塊會(huì)聚邊界稱會(huì)聚邊緣(convergent boundary)。俯沖帶上面反映震源活動(dòng)的地帶稱"貝尼奧夫地震帶(Benioff seismic zone)"。
　　2. soil "liquefaction"：土壤液化。土壤液化現(xiàn)象是指由于孔隙水壓力上升，有效應(yīng)力減小所導(dǎo)致的土壤從固態(tài)到液態(tài)的變化，飽水的疏松的粉、細(xì)砂土在振動(dòng)作用下突然破壞而呈現(xiàn)液態(tài)的現(xiàn)象。
　　3. localized：小范圍的
　　4. geotechnical engineering：巖土工程。
　　5. Oregon State University：俄勒岡州立大學(xué)，建校于1858年，位于美國俄勒岡州科瓦利斯，全校設(shè)11個(gè)學(xué)院，80多個(gè)專業(yè)，尤以農(nóng)科和工程最為突出。2008年俄勒岡州立大學(xué)的核能工程專業(yè)在全美大學(xué)中排名第9名。
　　6. water, drain and gas pipelines：自來水管道、排水管道和煤氣管道。"water, drain and gaspipelines" 即"water pipelines, drain pipelines and gas pipelines"。
　　7. some degree of soil liquefaction：某種程度的土壤液化
　　8. to reconsider the extent of liquefaction damage possibly occurring in situations such as this：本句的意思是：重新審視類似這次(持續(xù)時(shí)間長的)地震中因土壤液化而可能造成的毀壞的規(guī)模。