以闡明2004年印度洋大地震及海嘯成因為目標的國際海洋鑽探計畫

原文網址：www.sciencedaily.com/releases/2016/08/160808091256.htm

International ocean drilling expedition to understand causes of the Indian Ocean 2004 earthquake and tsunami

以闡明2004年印度洋大地震及海嘯成因為目標的國際海洋鑽探計畫

The devastating earthquake that struck North Sumatra and the Andaman and Nicobar Islands on Boxing Day (26 December) in 2004 caused a tsunami that inundated coastal communities around the Indian Ocean, killing over 250,000 people in 14 countries. That earthquake was caused by a slip on a subduction zone plate boundary fault beneath the eastern Indian Ocean.

在2004年節禮日(12月26日)當天，一場毀天滅地的大地震襲擊了蘇門答臘北部和安達曼—尼科巴群島(Andaman and Nicobar Islands)，同時引發的海嘯淹沒了印度洋周遭的沿海地帶，造成14個國家超過25萬人因此罹難。這場地震的成因是位於東印度洋板塊邊界，隱沒帶內部的斷層發生滑移所造成。

Now, over the coming weeks, a team of international researchers are returning to offshore Sumatra to collect marine sediments, rocks and fluids from this particular zone for the first time to gain a better understanding of the materials and to collect data for predicting how they behave in fault zones to generate large earthquakes.

時至今日，一組國際研究團隊在接下來的數周將會返回蘇門答臘外海，首次針對此區域的海洋沉積物、岩石和流體進行採樣，以更加瞭解這些物質的性質，並且蒐集數據來預測它們在斷層帶的行為如何導致大地震發生。

Throughout August and September the researchers, including experts from Ocean and Earth Science at the University of Southampton will spend two months on board the drilling vessel JOIDES Resolution as part of the International Ocean Discovery Programme (IODP). The Expedition, number 362 of the IODP, involves 33 scientists and two educators from 13 countries including Professors Lisa McNeill and Tim Henstock from the University of Southampton. Professor McNeill is one of the Expedition leaders along with Associate Professor Brandon Dugan of the Colorado School of Mines and Dr Katerina Petronotis of the IODP.

作為國際海洋發現計畫(IODP)中的一部分，包含南安普敦大學海洋與地球科學專家在內的研究人員，將會利用八月及九月兩個月的時間在鑽探船「聯合果敢號」上進行研究。來自13個國家的33名科學家和2名教育學者參與了這班IODP中編號為362的研究航次，其中包括了南安普敦大學的教授 Lisa McNeill和Tim Henstock。 McNeill教授是這次科學考察的主持人之一，另外兩名主持人則是科羅拉多礦業學院的副教授Brandon Dugan和 IODP的 Katerina Petronotis博士。

"We are very excited that the project is about to start as it has taken many years of preparation and the dedication of a large team of scientists from around the world," said Professor McNeill. "We have an excellent team onboard and we hope the results will help us understand what controls the size of the very largest earthquakes on Earth, particularly following the enormous numbers of casualties due to subduction earthquakes and tsunamis in the last 10-15 years.

「由世界各地科學家組成的團隊投注大量心力籌備多年的計畫終於要開始實行，對此我們感到十分興奮。」 McNeill教授表示。「我們在這艘船上擁有一組相當優秀的團隊，希望成果可以讓我們瞭解是什麼機制決定了地球上超大規模地震的大小，尤其是在過去10到15年來有許多人於隱沒帶產生的地震及伴隨的海嘯事件中罹難之後。」

"The Boxing Day earthquake of 2004 and the Japan Tohoku-oki earthquake in 2011 both ruptured to much shallower depths than expected, producing very large earthquakes and tsunami, and prompting a re-evaluation of earthquake slip potential and of the properties of shallow subduction faults," Professor McNeill continued. "Subsequent large magnitude earthquakes have struck this margin since 2004, including unusually large earthquakes in the Indian plate offshore North Sumatra in 2012. Therefore developing a better understanding of earthquake and tsunami behavior and potential is a priority for local communities, for the wider Indian Ocean, and for related subduction zones."

「2004年節禮日地震和2011年日本東北衝地震產生的破裂都延伸至比預期中淺了許多的地方，因而造成晃動相當劇烈的地震及巨型海嘯。這促使我們去重新評估淺層隱沒帶斷層發生滑移而產生地震的可能性及斷層本身的性質。」 McNeill教授繼續說。「自2004年開始這道板塊邊界後來也發生了數起大規模地震，包括2012年發生在蘇門答臘北部，印度板塊外海地區一場非常大型的地震。因此對當地居民，甚至是生活在印度洋周遭及其他類似隱沒帶附近的人民而言，當務之急是要更深入了解地震與海嘯的模式和發生的可能性。」

Professor McNeill explained that the North Sumatran subduction margin has an unusual structure and morphology that is likely influenced by the properties of the sediments and rocks forming the margin.

據McNeill教授解釋，蘇門答臘北部的隱沒性板塊邊界可能受到岩石及沉積物組成的性質影響，造成其構造與形貌相當特殊。

"Although our understanding of this margin's structure and development has increased enormously since 2004 due to marine geophysical data collection, as yet very little is known of the properties of the materials that make up this subduction zone," she continued. "This project will investigate how materials coming into the system drive shallow earthquake rupture and influence the shape of the continental margin. Our ultimate goal is to understand the hazard potential for this margin, and eventually others with similar material properties and margin morphology.

「雖然自2004年以來從當地海域蒐集了大量地球物理觀測數據，讓我們對此板塊邊界的構造及發育增加了許多瞭解，但是關於隱沒帶組成物質的性質我們仍所知甚少。」她繼續解釋。「這項計畫將會研究這些物質如何參與誘發淺層地震發生的系統，以及對板塊邊界形貌的影響。我們的終極目標是瞭解這段板塊邊緣可能發生的潛在災害，最後可以推及其他組成性質和型態類似的板塊邊緣。」

"This ocean drilling expedition will for the first time drill scientific boreholes within the sediments entering this subduction zone, including the layer of sediment that eventually develops into the earthquake-generating fault," Professor Henstock explained. "We know the sediments are of deep sea and terrestrial origin, including those eroded from the high Himalayas and transported thousands of kilometres into the Bay of Bengal and eastern Indian Ocean. But we do not know how the sediments change as they become physically and chemically altered as the sediment section builds up to 4-5 km thickness before reaching the subduction zone.

「這次的海洋鑽探計畫是史上首度對進入這條隱沒帶的沉積物進行鑽井的科學計畫。包括沉積物在內，鑽探深度最終會到達產生地震的斷層所在位置。」 Henstock教授如此解說。「我們知道這些沉積物的來源為深海及陸源，甚至含有從高聳的喜馬拉雅山侵蝕下來，傳輸數千公里直到孟加拉灣和東印度洋的沉積物。但我們仍不瞭解在到達隱沒帶之前，這些沉積物在累積4-5公里厚的過程中發生的物理化學變化。」

"Burial and increased temperatures also affect fluids within the sediment pile, and these are very important for earthquake fault behavior," Professor Henstock concluded. "Sampling and measuring the properties of the materials in situ and then extrapolating their properties to greater burial depths using modeling techniques and lab experiments will be important goals of this project."

「埋藏作用跟逐漸升高的溫度會影響沉積物當中的流體，而流體會對地震斷層的行為產生深遠影響。」 Henstock教授總結。「從現地採集這些物質的樣本並且測量其性質之後，利用模擬技術和實驗室試驗來外推這些性質在埋藏深度極深時的數值，是這項計畫的重要目標之一。」

引用自：University of Southampton. "International ocean drilling expedition to understand causes of the Indian Ocean 2004 earthquake and tsunami." ScienceDaily. ScienceDaily, 8 August 2016.