Seismotectonic, rupture process, and earthquake-hazard aspects of the 2003 December 26 Bam, Iran, earthquake
Seismotectonic, rupture process, and earthquake-hazard aspects of the 2003 December 26 Bam, Iran, earthquake
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DOI：
10.1111/j.1365-246x.2006.03056.x
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发表时间：
2006-09
影响因子：
2.8
通讯作者：
J. Jackson;M. Bouchon;E. Fielding;G. Funning;M. Ghorashi;D. Hatzfeld;H. Nazari;B. Parsons;K. Priestley;M. Talebian;M. Tatar;R. Walker;T. Wright
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文献类型：
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作者：
J. Jackson;M. Bouchon;E. Fielding;G. Funning;M. Ghorashi;D. Hatzfeld;H. Nazari;B. Parsons;K. Priestley;M. Talebian;M. Tatar;R. Walker;T. Wright
摘要2003年伊朗南部巴姆发生的M w 6.6灾难性地震引起了广泛关注，并通过合成孔径雷达、远震地震学、余震研究、强地面运动、地貌学、遥感和地面野外工作等大量观测进行了研究。许多报告都集中在一个或其他数据类型的细节上，产生的解释要么与其他数据冲突，要么没有答案。本文试图将所有可用的数据类型放在一起，以产生2003年同震断层的连贯图像，并研究其对该地区活动构造和持续地震危险的影响。我们的结论是，主震中超过80%的力矩释放发生在从巴姆市向南延伸约15 km的近垂直右行走滑断层上，最大滑动量为o2 mb，主要限于2 - 7 km的深度范围。对巴姆强地面运动记录的分析与这一观点一致，并表明该市的极端破坏至少部分可归因于巴姆地面运动的增强，因为巴姆位于向北传播的破裂的末端。主震中的滑动很少到达地球表面，更重要的是，余震揭示了断层系统较深部分的12 km垂直范围在同震破裂面下方8 - 20 km深度处保持未破裂。这可能对重建后的巴姆市构成巨大的地震危险。我们认为，在Bam-Baravat悬崖（一个不对称的背斜脊，是该地区最突出的地貌特征）处，在一个向西倾斜的盲断层上，在5 - 7公里的有限深度处发生了一些逆冲滑动（高达2米，不到释放的地震矩的20%）。该断层在2003年没有在浅层发生明显破裂，它也可能代表着持续的地震危险。城市北部广泛分布的地表破裂显然与深度的大量滑动无关，可能是与破裂向北传播有关的地面运动增强的结果。在巴姆断层可能是在一个空间分离（“分区”）的早期阶段之间的反向和走滑组件的斜收敛跨区域。这样的分离在大陆上很常见，尽管在这种情况下，两个断层之间的滑动矢量仅相差2000万，因为在逆冲断层上仍然存在大量的走滑分量。巴姆地震是一系列涉及沿着卢特沙漠西部边缘沿着断层的大地震之一。除了巴姆本身附近断层的未破裂部分外，邻近未破裂的断层，特别是南部沿着杰贝勒巴雷兹山脉的盲冲断层和西部萨尔维斯坦的走滑断层，也代表了持续和重大的危险。
SUMMARY The catastrophic 2003 M w 6.6 Bam earthquake in southern Iran attracted much attention, and has been studied with an abundance of observations from synthetic aperture radar, teleseismic seismology, aftershock studies, strong ground motion, geomorphology, remote sensing and surface field work. Many reports have focused on the details of one or other data type, producing interpretations that either conflict with other data or leave questions unanswered. This paper is an attempt to look at all the available data types together, to produce a coherent picture of the coseismic faulting in 2003 and to examine its consequences for active tectonics and continuing seismic hazard in the region. We conclude that more than 80 per cent of the moment release in the main shock occurred on a near-vertical right-lateral strike-slip fault extending from the city of Bam southwards for about 15 km, with slip of up t o2mb utmostly restricted to the depth range 2‐7 km. Analysis of the strong ground motion record at Bam is consistent with this view, and indicates that the extreme damage in the city can be attributed, at least in part, to the enhancement of ground motion in Bam because of its position at the end of the northward-propagating rupture. Little of the slip in the main shock reached the Earth’s surface and, more importantly, aftershocks reveal that ∼12 km vertical extent of a deeper part of the fault system remained unruptured beneath the coseismic rupture plane, at depths of 8‐20 km. This may represent a substantial remaining seismic hazard to the reconstructed city of Bam. We believe that some oblique-reverse slip (up to 2 m, and less than 20 per cent of the released seismic moment) occurred at a restricted depth of 5‐7 km on a blind west-dipping fault that projects to the surface at the Bam-Baravat escarpment, an asymmetric anticline ridge that is the most prominent geomorphological feature in the area. This fault did not rupture significantly at shallow levels in 2003, and it may also represent a continuing seismic hazard. Widespread distributed surface ruptures north of the city are apparently unrelated to substantial slip at depth, and may be the result of enhanced ground motion related to northward propagation of the rupture. The faulting at Bam may be in the early stages of a spatial separation (‘partitioning’) between the reverse and strike-slip components of an oblique convergence across the zone. Such a separation is common on the continents, though in this case the slip vectors between the two faults differ only by ∼20 ◦ as a substantial strike-slip component remains on the obliquereverse fault. The Bam earthquake is one in a series of large earthquakes involving faulting along the western edge of the Lut desert. In addition to the unruptured parts of the faults near Bam itself, continuing and substantial hazard is represented by unruptured neighbouring faults, particularly blind thrusts along the Jebel Barez mountains to the south and strike-slip faulting at Sarvestan to the west.