Reports of “earthquake lights,” like the ones seen in videos captured before last Friday’s 6.8-magnitude earthquake in Morocco, go back centuries to ancient Greece. These outbursts of bright, dancing light in different colors have long puzzled scientists, and there’s still no consensus on what causes them, but they are “definitely real,” said John Derr, a retired geophysicist who used to work at the U.S. Geological Survey. He has coauthored several scientific papers on earthquake lights, or EQL. “Seeing EQL depends on darkness and other favorability factors,” he explained in an email. He said the recent video from Morocco shared online looked like the earthquake lights caught on security cameras during a 2007 quake in Pisco, Peru. Juan Antonio Lira Cacho, a physics professor at Universidad Nacional Mayor de San Marcos in Peru and the Pontifical Catholic University of Peru, who has studied the phenomenon, said cell phone video and the widespread use of security cameras has made studying earthquake lights easier. Earthquake lights can take several different forms.Sometimes, the lights may appear similar to ordinary lightning, or they may be like a luminous band in the atmosphere akin to polar aurora. Other times they resemble glowing spheres floating midair. They may also look like small flames flickering or creeping along or near the ground or larger flames emerging from the ground. To better understand earthquake lights, Derr and his colleagues gathered information on 65 American and European earthquakes associated with trustworthy reports of earthquake lights dating back to 1600. They shared their work in a 2014 paper published in the journal Seismological Research Letters. The researchers found that some 80% of the EQL occurrences studied were observed for earthquakes with magnitudes greater than 5.0. In most cases, the phenomenon was observed shortly before or during the seismic event, and it was visible up 600 kilometers from the quake epicenter. The 2014 study also found that the vast majority of earthquakes linked to luminous phenomena occurred within tectonic plates, rather than at their boundaries. One theory explains that when certain defects or impurities in crystals in rocks are put under mechanical stress — such as during the build-up of tectonic stresses before or during a major earthquake — they instantly break apart and generate electricity. Rock is an insulator that, when mechanically stressed, becomes a semiconductor. Other theories about what causes earthquake lights include static electricity produced by the fracturing of rock and radon emanation, among many others. (SD-Agencies) Words to Learn 相關詞匯 【地震的】dìzhèn de seismic relating to or caused by an earthquake 【絕緣體】juéyuántǐ insulator a material that is a poor conductor (as of electricity or heat) 有人在上周五摩洛哥6.8級地震前拍攝到的視頻中看到了“地震光”，事實上，關于這一現象的報道可以追溯到幾個世紀前的古希臘。曾在美國地質調查局工作的退休地球物理學家約翰?德爾說地震光“絕對真實存在”。他曾與他人合作撰寫了多篇關于地震光的科學論文。 他在一封電子郵件中解釋說：“能否看到地震光取決于周圍環境的黑暗程度和其他因素。他說最近網上流傳的摩洛哥視頻看起來很像2007年秘魯皮斯科地震時監控攝像頭捕捉到的地震光。 秘魯國立圣馬科斯大學和秘魯天主教宗座大學的物理學教授胡安?安東尼奧?里拉?卡喬曾研究過這一現象。他說手機視頻和遍布的監控攝像頭使得研究地震光更容易。 地震光有幾種不同的形式。它有時看起來像普通閃電或者大氣中的發光帶，類似極光。其他時候，它們就像漂浮在半空中的發光球體，也可能像沿著地面或靠近地面閃爍蠕動的小火焰，或者從地下冒出的大火焰。 為了更好地了解這個現象，德爾和同事收集了65次此前發生在美國和歐洲的地震信息，都有關于地震光的可信報道，最早可追溯到 1600 年。2014 年他們在《地震學研究快報》雜志上發表了一篇論文來分享研究成果。 研究發現，在有記錄的地震光事件中，約 80% 是在震級大于 5.0 的地震中觀察到的。在大多數情況下，地震光是在地震發生前不久或地震期間觀測到的，在距離震中600公里的范圍內都能看見。 2014 年的研究還發現，絕大多數有地震光的地震都發生在板塊構造內部，而非板塊邊緣。 有一種理論解釋說，當巖石中晶體的某些缺陷或雜質受到機械應力時--例如在大地震前或大地震時積累的構造應力--它們會瞬間破裂并產生電能。巖石是絕緣體，但受到機械應力時會變成半導體。 關于地震發光原因，其他理論包括巖石斷裂產生的靜電和氡散發等。 (Translated by Debra) | 