Variability in surface rupture between successive earthquakes on the Suusamyr Fault, Kyrgyz Tien Shan: implications for palaeoseismology
Variability in surface rupture between successive earthquakes on the Suusamyr Fault, Kyrgyz Tien Shan: implications for palaeoseismology
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DOI：
10.1093/gji/ggy457
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发表时间：
2018-10
影响因子：
2.8
通讯作者：
E. Ainscoe;K. Abdrakhmatov;S. Baikulov;A. Carr;A. Elliott;C. Grützner;R. Walker
中科院分区：
文献类型：
--
作者：
E. Ainscoe;K. Abdrakhmatov;S. Baikulov;A. Carr;A. Elliott;C. Grützner;R. Walker
地表断层陡坎和古地震槽的解释是估计断层滑动率、地震复发率和灾害评估最大震级的关键组成部分。这些分析通常依赖于这样一种假设，即连续的地震都破坏了地表，而这些破坏是由地形记录的，或者是由暴露在海沟中的沉积物记录的。1992年吉尔吉斯斯坦苏萨米尔Mw 7.2地震显然是这种分析的一个有问题的案例，因为它的破裂显示出明显的位移，但只被映射为沿着断层的沿着小的、不同的部分破坏了表面。在这里，我们提出的调查结果进行了沿着苏萨米尔故障，以确定是否是这样的情况。地震后发现了两组破裂艾德。它们的位移异常短，并被25公里的差距分开。利用卫星图像、高分辨率数字高程模型和古地震槽探，我们首先重新评估了1992年断裂的分布，然后重建了全新世地震记录，以确定1992年地震在多大程度上代表了该断层的断裂行为。我们发现了至少两个史前地表破裂地震在全新世的证据：一个是3000万年和一个> 8000万年，沿着现代事件，给出了13000年和15000年的复发间隔。在1992年破裂段之间的空间间隙内，有明显的史前地表破裂，每次史前地震的破裂都是不连续的。我们的结论是，在Suusamyr断层上连续地震的表面破裂模式存在显著的变化，这对从逆冲断层崖获得的古地震记录的完整性有影响。
Interpretation of surface fault scarps and palaeoseismic trenches is a key component of estimating fault slip rates, earthquake recurrence rates and maximum magnitudes for hazard assessments. Often these analyses rely on the assumption that successive earthquakes all breached the surface and that the ruptures are recorded topographically, or by the deposits exposed in a trench. The M w 7.2 1992 Suusamyr earthquake, Kyrgyzstan, is an apparently problematic case for such analyses because its ruptures show significant displacement but are only mapped as having broken the surface along small, disparate portions of the fault. Here we present the results of surveys conducted along the Suusamyr Fault to establish whether that is the case. Two sets of ruptures were identified following the earthquake. They are unusually short for their displacement and are separated by a 25 km gap. Using satellite imagery, high-resolution digital elevation models and palaeoseismic trenching we first reassess the distribution of the 1992 ruptures and then reconstruct the Holocene earthquake record to establish the extent to which the 1992 earthquake is representative of the rupture behaviour of this fault. We find evidence for at least two prehistoric surface rupturing earthquakes in the Holocene: one ∼ 3 ka and one > 8 ka that, along with the modern event, gives recurrence intervals of ∼ 3 kyr and ∼ 5 kyr. Within spatial gaps between segments of the 1992 ruptures there are clear prehistoric surface ruptures and the ruptures in each prehistoric earthquake were discontinuous. We conclude that there is significant variability in the surface rupture pattern of successive earthquakes on the Suusamyr Fault, with implications for the completeness of palaeoseismic records obtained from thrust scarps.