比萨斜塔为何能经历4次大地震而不倒？
<p>虽然有5度的倾斜度，但58米高的比萨斜塔自1280年以来经历至少4次大地震，为何还能屹立不倒？科学家最近给出了答案。</p><p><span word="New">New</span> <span word="research">research</span> <span word="has">has</span> <span word="revealed">revealed</span> <span word="how">how</span> <span word="the">the</span> <span word="iconic">iconic</span> <span word="Leaning">Leaning</span> <span word="Tower">Tower</span> <span word="of">of</span> <span word="Pisa">Pisa</span> <span word="has">has</span> <span word="managed">managed</span> <span word="to">to</span> <span word="stay">stay</span> <span word="standing">standing</span> – <span word="and">and</span> <span word="intact">intact</span> – <span word="in">in</span> <span word="the">the</span> <span word="face">face</span> <span word="of">of</span> <span word="four">four</span> <span word="strong">strong</span> <span word="earthquakes">earthquakes</span> <span word="and">and</span> <span word="a">a</span> <span word="precarious">precarious</span> <span word="lean">lean</span> <span word="of">of</span> <span word="five">five</span> <span word="degrees">degrees</span>.</p><p>意大利的标志性建筑比萨斜塔有5度的倾斜度，而且还历经4次大地震，却依然屹立不倒，完好无损，最新的研究揭开了这个谜底。</p><p><span word="The">The</span> <span word="vulnerability">vulnerability</span> <span word="of">of</span> <span word="the">the</span> <span word="Unesco">Unesco</span> <span word="World">World</span> <span word="Heritage">Heritage</span> <span word="Site">Site</span> <span word="has">has</span> <span word="mystified">mystified</span> <span word="engineers">engineers</span> <span word="and">and</span> <span word="scientists">scientists</span> <span word="for">for</span> <span word="millennia">millennia</span>. <span word="Moderate">Moderate</span> <span word="seismic">seismic</span> <span word="activity">activity</span> <span word="was">was</span> <span word="expected">expected</span> <span word="to">to</span> <span word="significantly">significantly</span> <span word="damage">damage</span> <span word="the">the</span> 58<span word="m">m</span> <span word="tall">tall</span> <span word="Tower">Tower</span>, <span word="or">or</span> <span word="even">even</span> <span word="result">result</span> <span word="in">in</span> <span word="collapse">collapse</span> <span word="but">but</span>, <span word="incredibly">incredibly</span>, <span word="this">this</span> <span word="has">has</span> <span word="not">not</span> <span word="happened">happened</span>.</p><p>比萨斜塔高58米，被评为联合国教科文组织世界遗产。一千年来，比萨斜塔的脆弱性一直令工程师和科学家们困惑不已。按说，中度地震活动应该就能导致它严重受损甚至倒塌，但现实中这样的情形并未发生，令人不可思议。</p><p><span word="A">A</span> <span word="research">research</span> <span word="group">group</span> <span word="of">of</span> 16 <span word="engineers">engineers</span> <span word="at">at</span> <span word="the">the</span> <span word="University">University</span> <span word="of">of</span> <span word="Bristol">Bristol</span> <span word="has">has</span> <span word="now">now</span> <span word="discovered">discovered</span> <span word="that">that</span> <span word="the">the</span> <span word="considerable">considerable</span> <span word="height">height</span> <span word="and">and</span> <span word="stiffness">stiffness</span> <span word="of">of</span> <span word="the">the</span> <span word="Tower">Tower</span>, <span word="combined">combined</span> <span word="with">with</span> <span word="the">the</span> <span word="softness">softness</span> <span word="of">of</span> <span word="the">the</span> <span word="foundation">foundation</span> <span word="soil">soil</span>, <span word="ensure">ensure</span> <span word="it">it</span> <span word="doesn">doesn</span>’<span word="t">t</span> <span word="resonate">resonate</span> <span word="with">with</span> <span word="earthquake">earthquake</span> <span word="ground">ground</span> <span word="motion">motion</span>.</p><p>英国布里斯托尔大学一个由16名工程师组成的研究小组如今发现，比萨斜塔如此的高度及其坚硬的建筑材料与松软的地基土壤结合在一起，使它不会与地震发生时的地表活动产生共振。</p>
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