Persistent elastic behavior above a megathrust rupture patch: Nias island, West Sumatra
Persistent elastic behavior above a megathrust rupture patch: Nias island, West Sumatra
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巨型逆冲破裂带上方的持续弹性行为：西苏门答腊岛尼亚斯岛
DOI：
10.1029/2008jb005684
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发表时间：
2008
影响因子：
--
通讯作者：
T. Farr
中科院分区：
文献类型：
--
作者：
R. Briggs;K. Sieh;W. Amidon;J. Galetzka;D. Prayudi;I. Suprihanto;N. Sastra;B. Suwargadi;D. Natawidjaja;T. Farr
我们量化弧前变形使用化石礁来测试地震周期模型中通常假设的弧前滞弹性变形可以忽略不计。升高的珊瑚微环礁，古珊瑚礁的单位，和贝壳滩平原表明，苏门答腊外弧岛尼亚斯经历了一个复杂的模式，相对缓慢的长期隆起和沉降在全新世。在2005年Mw8.7的Sunda巨型逆冲断层破裂期间，同一个岛屿上升到2.9米。2005年和全新世隆起模式之间的不匹配，沿着整体低速率的全新世变形，反映了主导的弹性应变积累和释放沿着这一部分的巽他外弧高和相对次要的作用，上部板块变形，以适应长期的板块收敛。对于经历了超过0.25 m同震隆起的场地，2005年隆起的部分将被永久保留，通常<4%。中全新世以来的平均抬升速率介于1.5至-0.2毫米/年之间，最高的是尼亚斯东海岸，2005年同震抬升几乎为零。长期的隆升和沉降模式与北部的尼亚斯沿着密集褶皱的缓慢变形和东南部的向沟倾斜逆冲断层相一致。低全新世构造抬升率提供了良好的地貌和地层保存中全新世相对海平面高，这是正在进行的0.7.3万年，并持续到0.22万年。
We quantify fore-arc deformation using fossil reefs to test the assumption commonly made in seismic cycle models that anelastic deformation of the fore arc is negligible. Elevated coral microatolls, paleoreef flats, and chenier plains show that the Sumatran outer arc island of Nias has experienced a complex pattern of relatively slow long-term uplift and subsidence during the Holocene epoch. This same island rose up to 2.9 m during the Mw 8.7 Sunda megathrust rupture in 2005. The mismatch between the 2005 and Holocene uplift patterns, along with the overall low rates of Holocene deformation, reflects the dominance of elastic strain accumulation and release along this section of the Sunda outer arc high and the relatively subordinate role of upper plate deformation in accommodating long-term plate convergence. The fraction of 2005 uplift that will be retained permanently is generally <4% for sites that experienced more than 0.25 m of coseismic uplift. Average uplift rates since the mid-Holocene range from 1.5 to −0.2 mm/a and are highest on the eastern coast of Nias, where coseismic uplift was nearly zero in 2005. The pattern of long-term uplift and subsidence is consistent with slow deformation of Nias along closely spaced folds in the north and trenchward dipping back thrusts in the southeast. Low Holocene tectonic uplift rates provide for excellent geomorphic and stratigraphic preservation of the mid-Holocene relative sea level high, which was under way by ∼7.3 ka and persisted until ∼2 ka.