Beach ridge patterns in West Aceh, Indonesia, and their response to large earthquakes along the northern Sunda trench
Beach ridge patterns in West Aceh, Indonesia, and their response to large earthquakes along the northern Sunda trench
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印度尼西亚西亚齐的海滩山脊模式及其对巽他海沟北部大地震的响应
DOI：
10.1016/j.quascirev.2014.10.014
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
S. U. Sudrajat
中科院分区：
文献类型：
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作者：
K. Monecke;C. Templeton;W. Finger;B. Houston;S. Luthi;B. McAdoo;E. Meilianda;J. Storms;D. Walstra;Razali Amna;N. Hood;Francis J. Karmanocky;Nurjanah;I. Rusydy;S. U. Sudrajat
沿着活动边缘的海滩脊平原的形态可用于重建大型逆冲断层地震期间的海岸沉降。在这里，我们使用卫星图像和自动水平测量重建一个新的海滩脊沿着亚齐西部海岸10公里长的延伸后，在苏门答腊-安达曼大地震和连续的海啸在2004年12月完全摧毁的海滩。西部亚齐海岸的特点是山脊和洼地地形反映了海岸线的长期扩张。从山脊之间的沼泽沉积物中获得的放射性碳年代显示，在过去的1000年中，平均每年的降水量为1.3-1.8米。由于2004年同震沉降0.5-1 m和海啸淹没，最向海的海滩山脊被破坏，海岸线平均向陆地后退110 m，代表65-85年的平均海退。然而，到2006年，一个新的22米宽的山脊已经形成。在接下来的几年里，海岸线又增加了30米，但尚未恢复到2004年12月之前的位置。除了空间数据外，2009年、2012年和2013年进行的地形调查表明，新形成的海滩脊的脊顶比更内陆的老海滩脊的脊顶高0.8-1.3米。新海脊的源物质很可能是2004年海啸的回流向海输送并储存在上海岸面的沙子。在海啸发生后的几个月或几年里，这些沉积物被常规的海岸过程重新加工，并被运回海岸，导致重建一个较高的海滩脊，与海岸的垂直位移和由此产生的较高的相对海平面相平衡。新形成的海脊的保存潜力取决于海岸系统内沉积物的可用性，以平衡由于震后快速抬升而引起的海岸剖面调整。在亚齐，地震改变的海滩山脊形态似乎可能得到保存，在距离海岸线640米处可以发现另一个突出的山脊。它很可能是在大约600年前的一次特大逆冲地震和海啸之后形成的，与该地区的沉积物和珊瑚记录相匹配。
The morphology of beach ridge plains along active margins can be used to reconstruct coastal subsidence during large megathrust earthquakes. Here we use satellite imagery and automatic level surveys to reconstruct the build-up of a new beach ridge along a 10 km long stretch of the western Acehnese coast after the complete destruction of the beach during the great Sumatra -Andaman earthquake and successive tsunami in December 2004. The western Acehnese coast is characterized by ridge and swale topography reflecting the long-term progradation of the coastline. Radiocarbon dates obtained from marshy deposits in between ridges indicate an average progradation rate of 1.3–1.8 m per year over the last 1000 years. As a result of coseismic subsidence of 0.5–1 m and tsunami inundation in 2004, the most seaward beach ridge was destroyed and the coastline receded on average 110 m landward representing 65–85 years of average progradation. However, by 2006 a new 22 m wide ridge had formed. In the following years the coast prograded by an additional 30 m, but has not yet recovered to its pre-December 2004 position. In addition to the spatial data, topographic surveys conducted in 2009, 2012 and 2013 indicate that the crest of the newly formed beach ridge is 0.8–1.3 m higher than the crests of older beach ridges further inland. The source material for the new ridge is most likely sand transported seaward by the back flow of the 2004 tsunami and stored on the upper shoreface. In the months and years after the tsunami, this sediment is reworked by regular coastal processes and transported back to shore, leading to the reconstruction of a higher beach ridge in equilibrium with the vertical displacement of the coast and the resulting higher relative sea level. The preservation potential of the newly formed ridge depends on sediment availability within the coastal system to balance coastal profile adjustments due to rapid postseismic uplift. In Aceh, the preservation of seismically modified beach ridge morphology seems likely and another prominent ridge can be found in 640 m distance to the shoreline. It most likely formed in the aftermath of a previous megathrust earthquake and tsunami about 600 years ago matching sediment and coral records for this region.