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The author:(作者)aaapublished in(发表于) 2013/12/18 9:51:15 Former Vice President of the Chinese Academy of engineering， denied that earthquakes associated with the three gorges project
Frequent earthquakes and the three gorges project related?
"Net smell" play back
On December 16, in Enshi Tujia and Miao autonomous prefecture, Hubei Province, badong County, a 5.1-magnitude earthquake. That evening an earthquake, some netizens issued opinions saying that "this is the fault of the three Gorges Dam."
In recent years, the once strong earthquakes in Western China, about the construction of the three Gorges Dam could trigger speculation and controversy of this earthquake will break out. In April this year, Lushan when the earthquake struck, some netizens have expressed such doubts. Building 20 in the three gorges project, the hub successfully runs the 10 anniversary of the occasion of the successful achievement of the 175-meter water storage for 4 consecutive years, credence to that view again.
Earthquake in Wenchuan earthquake, earthquake in Lushan, Enshi is associated with TGP? Wonder in three gorges project induced earthquake in the Western region? In this regard, the impoundment of three gorges project pilot phase assessment project team leader, former Vice President of the Chinese Academy of engineering academician Shen Guofang appraised to be responded to.
Reporter: in General, the gleaming cities of water conservancy project whether the dam will cause earthquakes?
Shen Guofang appraised: sure is, gleaming cities dam will induce earthquakes, but magnitude is generally small, often dominated by tremors and tremors, because deep penetration of water along the fault may result in reduced its shear strength, intense pressure and filling of the reservoir formed by the dam itself can also cause certain changes in the geological structures.
Current academic recognition, the stereotype of reservoir-induced earthquake, the reservoir may trigger a near distance area and is close to the limit of seismogenic fault, deep penetration of water along the fault result in reduced its shear strength, is the main reason triggering earthquakes. According to hydrogeological conditions, kushui distance does not exceed the Bank's first watershed to the outside, usually about 3 per cent from the Bank, will not be greater than 10-kilometer.
Relative to the geological structure of energy by itself, changes brought pressure on the dam is still relatively small, the dam triggered an earthquake magnitude is quite small. Dam triggered an earthquake occurred early in the dam was built, as time goes by, stabilise following geological structure of the dam, dam is raised further reduces the probability of an earthquake.
Reporter: from the perspective of monitoring data, how earthquakes in three Gorges area?
Shen Guofang appraised: monitoring data indicate that, during the impoundment in three Gorges reservoir area dominated by tremors and tremors of seismic activity, mainly raised by Karst, caves soak, recorded in three Gorges area of M4.1 earthquake was the largest initial impoundment period took place in November 2008, much less than the initial design verification report "M5.5 can be considered" predictive value.
Reporter: Wenchuan earthquake, Lushan earthquake earthquake induced by TGP reservoir?
Shen Guofang appraised: the answer is in the negative, the three Gorges reservoir has no direct relationship with these two strong earthquakes in Southwest China. Wenchuan earthquake caused entirely from the Earth's interior. Artificial water storage reservoir induced seismicity, fall short of such high magnitude, factors of reservoir-induced earthquake, most less than five.
In addition, studies have shown that reservoir of reservoir-induced earthquake magnitude and volume there is no positive relationship, in addition, of three Gorges reservoir water ballast is small, relatively far from Wenchuan, to be sure, the earthquake has no connection with the three gorges project.
In fact, the Wenchuan earthquake and the earthquake in Lushan, in southern section of North-South seismic belt of Longmen mountain fault zone, is India caused by plate collision pushed Asian and European plate. Huangling Anticline, where the three Gorges Dam belonging to the Central Yangtze platform of Yangzi quasi platform fold belt, with two different earthquakes the regional tectonic conditions, there is no regional structural links.
Reporter: after the three Gorges reservoir have the potential to set off earthquakes?
Shen Guofang appraised: currently recorded the biggest earthquake in three Gorges reservoir M4.1, over time, caused by the three Gorges reservoir seismic level will further decline. In addition, sited in stable geological structure in three Gorges reservoir area, had taken into account the factors that might cause earthquakes, three Gorges reservoir induced earthquake possibility is very small. According to the design requirements, the three Gorges Dam able to withstand eight-magnitude earthquake, earthquake that occurred around the area are also generally do not pose a threat to safety of three Gorges reservoir.
At present, the Enshi Padang earthquake did not affect the normal operation of three gorges project. Monitoring shows that current BANK in TGP building and reservoir geology is in good condition, the indicators are within normal range. (Reporter Li Hui subaqueous)
频繁的地震与三峡工程有关吗？
“网闻”回放
12月16日13时4分，湖北省恩施土家族苗族自治州巴东县发生5.1级地震。发生地震的当天晚上，便有网友发布观点称“这又是三峡大坝惹的祸”。
近年来，一旦我国西部地区发生强震，有关建设三峡大坝有可能诱发本次大地震的猜测和争论便此起彼伏。今年4月，芦山地震发生时，有网民也曾表达过这种疑问。在三峡工程兴建20年、枢纽成功运行10周年暨连续4年成功实现175米蓄水之际，这种观点再次甚嚣尘上。
汶川地震、芦山地震、恩施地震是否与三峡工程有关？三峡工程到底会不会诱发西部地区大地震？对此，三峡工程试验性蓄水阶段性评估项目组组长、原中国工程院副院长沈国舫院士对此进行了回应。
记者：一般而言，水利工程兴修的大坝是否会引发地震？
沈国舫：可以肯定的是，兴修大坝一定会诱发地震，但震级一般较小，常以微震和极微震为主，因为库水沿断层深层渗透将导致其抗剪断强度降低，大坝本身和蓄水所形成的巨大压力也会导致地质构造发生一定变化。
目前学术界公认，对构造型水库诱发地震来说，水库蓄水只可能触发距离库区较近且已接近极限状态的发震断层，库水沿断层深层渗透导致其抗剪断强度降低，是触发地震的主要原因。根据水文地质条件，库水向外渗透距离不会超过库岸第一分水岭，一般距库岸边约3到5千米，不会大于10千米。
相对于地质构造本身所蕴含的能量，水库大坝带来的压力改变仍相对较小，因此大坝引发的地震一般震级很小。大坝引发的地震一般发生在大坝建成初期，随着时间推移，大坝下面的地质构造趋向稳定，大坝引发地震的概率会进一步减小。
记者：从监测数据看，三峡库区发生地震的状况如何？
沈国舫：监测数据表明，蓄水期间三峡库区的地震活动以微震和极微震为主，主要由岩溶、矿洞浸水引发，三峡库区记录到的最大地震是蓄水初期2008年11月发生的M4.1级，远小于初步设计论证报告提出的“可按M5.5级考虑”的预测值。
记者：汶川地震、芦山地震等强震是否由三峡水库诱发？
沈国舫：答案是否定的，三峡水库与这两次西南强震没有直接关系。汶川大地震完全由地球内部作用引起。人为蓄水的水库诱发地震，达不到这么高的震级，水库蓄水因素诱发地震，大多为五级以内。
此外，研究表明，水库诱发地震震级与水库容量没有正比关系，另外，三峡水库蓄水压载力小，距离汶川也比较远，因此可以肯定，此次大地震与三峡工程没有关系。
实际上，汶川地震和芦山地震发生在南北地震带南段的龙门山断裂带，是印度板块推挤碰撞亚欧板块造成的。而三峡大坝所在的黄陵背斜属于扬子准地台中部的上扬子台褶带，与这两次地震所处的区域构造条件截然不同，完全没有区域构造上的联系。
记者：三峡水库以后是否有引发大地震的可能？
沈国舫：目前三峡库区记录到的最大地震是M4.1级，随着时间推移，三峡水库可能引发的地震等级将进一步衰减。此外，三峡水库选址在地质构造稳定的地区，已考虑可能引发地震的因素，三峡水库诱发大地震的可能性很小。按照设计要求，三峡大坝能够抵御八级地震，因此库区周边发生的地震一般也不会对三峡水库的安全带来威胁。
目前，恩施巴东地震也未对三峡工程正常运行带来影响。监测显示，目前三峡枢纽建筑物和水库坡岸地质状况良好，各项指标均在正常范围内。(本报记者 李 慧 杨 君)
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