Three-dimensional surface displacement of the 2008 May 12 Sichuan earthquake (China) derived from Synthetic Aperture Radar: evidence for rupture on a blind thrust
Three-dimensional surface displacement of the 2008 May 12 Sichuan earthquake (China) derived from Synthetic Aperture Radar: evidence for rupture on a blind thrust
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DOI：
10.1111/j.1365-246x.2010.04807.x
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发表时间：
2010-12
影响因子：
2.8
通讯作者：
M. Michele;D. Raucoules;J. Sigoyer;M. Pubellier;N. Chamot‐Rooke
中科院分区：
文献类型：
--
作者：
M. Michele;D. Raucoules;J. Sigoyer;M. Pubellier;N. Chamot‐Rooke
摘要2008年5月12日，中国四川省龙门山（LMS）发生了7.9级地震，影响了一个中等历史地震活动的地区，此前几乎没有报道过主动缩短。近年来基于空间大地测量的研究已成功地反演了地震引起的远场地表位移，但近场（距断层±25 km）同震地表位移的约束条件仍然很差。因此，浅层断层几何形状和浅层同震滑动仍然很难解决。本文首次针对四川地震，结合联合收割机C波段和L波段合成孔径雷达（SAR）的上升道和下降道炮检距资料，反演了四川地震近同震区的三维地表位移。我们的数据，再加上一个简单的弹性位错模型，提供了新的结果，强烈建议存在一个盲目的逆冲断层罢工沿着范围前，并在地震期间的深度活跃。断裂的存在下，一个盲目的逆冲断层带来了新的证据，一个序列外的逆冲事件和新的元素来解释构造应变分配在LMS，这对地震危险性评估和长期演化的山区带具有重要意义。
SUMMARY The Sichuan earthquake, Mw 7.9, struck the Longmen Shan (LMS) range front, China, on 2008 May 12, affecting an area of moderate historical seismicity where little active shortening has been previously reported. Recent studies based on space geodesy have succeeded in retrieving the far field surface displacements caused by the earthquake, but the near field (±25 km from the faults) coseismic surface displacement is still poorly constrained. Thus, shallow fault geometry and shallow coseismic slip are still poorly resolved. Here, for the first time for this earthquake, we combine C and L-band Synthetic Aperture Radar offsets data from ascending and descending tracks to invert for the 3-D surface displacement in the near coseismic field of the Sichuan earthquake. Our data, coupled with a simple elastic dislocation model, provide new results strongly suggesting the presence of a blind thrust striking along the range front and being active at depth during the earthquake. The presence of a rupture on a blind thrust brings new evidence for an out-of-sequence thrusting event and new elements for interpreting the tectonic strain partitioning in the LMS, which has important implications both for seismic hazard assessment and long-term evolution of the mountain belt.