Fault slip in the 1997 Manyi, Tibet earthquake from linear elastic modelling of InSAR displacements
Fault slip in the 1997 Manyi, Tibet earthquake from linear elastic modelling of InSAR displacements
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DOI：
10.1111/j.1365-246x.2006.03318.x
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发表时间：
2007-06
影响因子：
2.8
通讯作者：
G. Funning;B. Parsons;T. Wright
中科院分区：
文献类型：
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作者：
G. Funning;B. Parsons;T. Wright
摘要 1997年曼依7.6级地震发生在西藏中北部地区，该地区植被稀疏，缺乏人类居住，为干涉合成孔径雷达（InSAR）研究提供了良好的条件。我们使用 ESA ERS-2 卫星获取的同震雷达图像对来构建地震引起的表面位移场的干涉图。结合光学卫星图像、高分辨率数字地形、干涉相关和方位偏移测量来绘制同震断层破裂的位置和范围；通过这样做，我们能够将断层带中突出的地貌特征与断层的弯曲联系起来。然后，我们使用与所映射的断层轨迹一致的弹性位错模型，测试一系列断层几何形状和滑移条件，以找到最能解释 InSAR 位移的组合。我们喜欢的模型包含断层倾角的反转，大约沿其长度的一半，发生在限制弯曲的位置。该模型断层上的滑动是不均匀的，有两个峰值滑动区域为 7 m 或更大，并且倾角滑动位移分量沿走向变化很大。该模型在拟合数据方面的成功意味着，同震干涉图中观察到的不对称性可以用局部断层几何形状来解释，而不是像早期作者建议的那样使用非线性弹性流变学。
SUMMARY The Mw 7.6 1997 Manyi earthquake occurred in an area of central northern Tibet where sparse vegetation coverage and a lack of human habitation provide excellent conditions for Interferometric Synthetic Aperture Radar (InSAR) studies. We use coseismic pairs of radar images acquired by the ESA ERS-2 satellite to construct interferograms of the surface displacement field due to the earthquake. The location and extent of the coseismic fault rupture are mapped using a combination of optical satellite imagery, high-resolution digital topography, interferometric correlation and azimuth offset measurements; in so doing, we are able to relate prominent geomorphic features in the fault zone to bends in the fault. Using elastic dislocation models consistent with this mapped fault trace, we then test a range of fault geometries and slip conditions to find the combination which best explains the InSAR displacements. Our favoured model contains a reversal in fault dip, approximately halfway along its length, occurring at the location of a restraining bend. Slip on this model fault is heterogeneous, with two areas of peak slip of 7 m or greater, and components of dip-slip displacement which vary significantly along-strike. The success of this model in fitting the data implies that an observed asymmetry in the coseismic interferograms can be explained in terms of the local fault geometry, rather than by using non-linear elastic rheologies as suggested by earlier authors.