Subarya Cecep, Chlieh Mohamed, Prawirodirdjo Linette, Avouac Jean-Philippe, Bock Yehuda, Sieh Kerry, Meltzner Aron J, Natawidjaja Danny H, McCaffrey Robert
National Coordinating Agency for Surveys and Mapping, Cibinong 16911, Indonesia.
Nature. 2006 Mar 2;440(7080):46-51. doi: 10.1038/nature04522.
The Sumatra-Andaman earthquake of 26 December 2004 is the first giant earthquake (moment magnitude M(w) > 9.0) to have occurred since the advent of modern space-based geodesy and broadband seismology. It therefore provides an unprecedented opportunity to investigate the characteristics of one of these enormous and rare events. Here we report estimates of the ground displacement associated with this event, using near-field Global Positioning System (GPS) surveys in northwestern Sumatra combined with in situ and remote observations of the vertical motion of coral reefs. These data show that the earthquake was generated by rupture of the Sunda subduction megathrust over a distance of >1,500 kilometres and a width of <150 kilometres. Megathrust slip exceeded 20 metres offshore northern Sumatra, mostly at depths shallower than 30 kilometres. Comparison of the geodetically and seismically inferred slip distribution indicates that approximately 30 per cent additional fault slip accrued in the 1.5 months following the 500-second-long seismic rupture. Both seismic and aseismic slip before our re-occupation of GPS sites occurred on the shallow portion of the megathrust, where the large Aceh tsunami originated. Slip tapers off abruptly along strike beneath Simeulue Island at the southeastern edge of the rupture, where the earthquake nucleated and where an M(w) = 7.2 earthquake occurred in late 2002. This edge also abuts the northern limit of slip in the 28 March 2005 M(w) = 8.7 Nias-Simeulue earthquake.
2004年12月26日的苏门答腊-安达曼地震是现代天基大地测量学和宽带地震学出现以来发生的首例矩震级M(w)>9.0的特大地震。因此，它为研究这些巨大且罕见事件之一的特征提供了前所未有的机会。在此，我们报告与该事件相关的地面位移估计值，这些估计值是利用苏门答腊岛西北部的近场全球定位系统（GPS）测量，并结合对珊瑚礁垂直运动的现场和遥感观测得出的。这些数据表明，此次地震是由巽他俯冲带巨型逆冲断层在超过1500公里的距离和小于150公里的宽度上破裂产生的。在苏门答腊岛北部近海，巨型逆冲断层的滑动超过20米，大部分发生在深度小于30公里处。大地测量和地震推断的滑动分布比较表明，在长达500秒的地震破裂后的1.5个月内，断层额外滑动了约30%。在我们重新占领GPS站点之前，地震滑动和非地震滑动都发生在巨型逆冲断层的浅部，这里也是亚齐大海啸的发源地。在破裂东南边缘的锡默卢岛下方，滑动沿走向突然减小，这里是地震的震源，2002年末曾发生过一次M(w)=7.2的地震。这个边缘也紧邻2005年3月28日M(w)=8.7的尼亚斯-锡默卢地震的滑动北界。
