MARUM-Center for Marine Environmental Sciences, University of Bremen, Post Office Box 330 440, D-28334 Bremen, Germany.
College of Earth, Ocean and Atmospheric Sciences, Oregon State University, 104 CEOAS Administration Building, Corvallis, OR 97331-5503, USA.
Science. 2017 May 26;356(6340):841-844. doi: 10.1126/science.aal3429.
Plate-boundary fault rupture during the 2004 Sumatra-Andaman subduction earthquake extended closer to the trench than expected, increasing earthquake and tsunami size. International Ocean Discovery Program Expedition 362 sampled incoming sediments offshore northern Sumatra, revealing recent release of fresh water within the deep sediments. Thermal modeling links this freshening to amorphous silica dehydration driven by rapid burial-induced temperature increases in the past 9 million years. Complete dehydration of silicates is expected before plate subduction, contrasting with prevailing models for subduction seismogenesis calling for fluid production during subduction. Shallow slip offshore Sumatra appears driven by diagenetic strengthening of deeply buried fault-forming sediments, contrasting with weakening proposed for the shallow Tohoku-Oki 2011 rupture, but our results are applicable to other thickly sedimented subduction zones including those with limited earthquake records.
2004 年苏门答腊-安达曼俯冲地震期间的板块边界断层破裂比预期更接近海沟，从而增大了地震和海啸的规模。国际大洋发现计划第 362 次考察队在苏门答腊北部近海采集了进入的沉积物，揭示了最近深部沉积物中淡水的释放。热模拟将这种淡水化与过去 900 万年中快速埋藏引起的温度升高驱动的无定形二氧化硅脱水联系起来。在板块俯冲之前预计会完全脱硅，这与流行的俯冲地震成因模型形成对比，后者认为在俯冲过程中会产生流体。苏门答腊近海的浅层滑移似乎是由深埋形成断层的沉积物的成岩强化驱动的，这与 2011 年东北-千岛浅层破裂所提出的弱化形成对比，但我们的结果适用于其他沉积层较厚的俯冲带，包括那些地震记录有限的俯冲带。
