Great earthquakes in low strain rate continental interiors: An example from SE Kazakhstan
Great earthquakes in low strain rate continental interiors: An example from SE Kazakhstan
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DOI：
10.1002/2015jb011925
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发表时间：
2015-08-01
影响因子：
3.9
通讯作者：
Schwenninger, J. -L.
中科院分区：
文献类型：
--
作者：
Campbell, G. E.;Walker, R. T.;Schwenninger, J. -L.
位于哈萨克斯坦东南部天山北部的Lepsy断层，从天山北部的一个分支——保加利亚Ala-tau的高山向东西向延伸120公里，进入低洼的哈萨克斯坦地台。这是一个活跃构造的例子，它连接了一个快速变形的山区和一个明显稳定的大陆地区，并遵循一个已知的古生代构造。现场观测和卫星观测显示，沿整个断层长度异常地保留了大约10米的垂直偏移。利用放射性碳和光学激发发光测年方法进行地貌分析和年代控制，表明该断崖形成于全新世，至少由两次大地震造成。最近的一次地震发生在距今大约400年之后的某个时候，很可能在一场里里外外的7.5-8.2级地震中使整个大约120公里长的断层破裂。利用数字高程模型和高分辨率卫星图像对Lepsy断层的运动学特征进行了表征，结果表明，该断层的主要运动方向为右反侧向运动，断层走向、倾角和滑动矢量方位角分别约为110°、50°S和317-343°S，与印度-欧亚板块碰撞相关的主要南北向缩短运动相一致。根据这些观察，并且由于如果在最近的过去它没有破裂，那么麻风断层的活动将很难确定，我们注意到，在低起伏和低应变率大陆内部没有已知的活动断层并不总是意味着没有地震危险。
The Lepsy fault of the northern Tien Shan, SE Kazakhstan, extends E-W 120km from the high mountains of the Dzhungarian Ala-tau, a subrange of the northern Tien Shan, into the low-lying Kazakh platform. It is an example of an active structure that connects a more rapidly deforming mountain region with an apparently stable continental region and follows a known Palaeozoic structure. Field-based and satellite observations reveal an approximate to 10m vertical offset exceptionally preserved along the entire length of the fault. Geomorphic analysis and age control from radiocarbon and optically stimulated luminescence dating methods indicate that the scarp formed in the Holocene and was generated by at least two substantial earthquakes. The most recent event, dated to sometime after approximate to 400years B.P., is likely to have ruptured the entire approximate to 120km fault length in a M-w 7.5-8.2 earthquake. The Lepsy fault kinematics were characterized using digital elevation models and high-resolution satellite imagery, which indicate that the predominant sense of motion is reverse right lateral with a fault strike, dip, and slip vector azimuth of approximate to 110 degrees, 50 degrees S, and 317-343 degrees, respectively, which is consistent with predominant N-S shortening related to the India-Eurasia collision. In light of these observations, and because the activity of the Lepsy fault would have been hard to ascertain if it had not ruptured in the recent past, we note that the absence of known active faults within low-relief and low strain rate continental interiors does not always imply an absence of seismic hazard.