The 1994 Sefidabeh (eastern Iran) earthquakes revisited: new evidence from satellite radar interferometry and carbonate dating about the growth of an active fold above a blind thrust fault
The 1994 Sefidabeh (eastern Iran) earthquakes revisited: new evidence from satellite radar interferometry and carbonate dating about the growth of an active fold above a blind thrust fault
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DOI：
10.1111/j.1365-246x.2005.02655.x
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发表时间：
2006
影响因子：
2.8
通讯作者：
B. Parsons;T. Wright;P. Rowe;J. Andrews;J. Jackson;R. Walker;M. Khatib;M. Talebian;E. Bergman-E.
中科院分区：
文献类型：
--
作者：
B. Parsons;T. Wright;P. Rowe;J. Andrews;J. Jackson;R. Walker;M. Khatib;M. Talebian;E. Bergman-E.
1994年，伊朗东部塞菲达贝附近发生了三起Mw～6级浅源地震，这些地震是在盲目逆冲作用下紧密相连的。在对震中地区远震波形、地貌和断层的早期研究中，有人认为这些地震与盲冲断层系统上方山脊的生长有关，该断层系统的活动可以通过其对地表排水的影响来检测。在这项研究中，我们提出了一个SAR干涉图，它可以精确确定同震表面位移的位置和数量，表明Sefidabeh序列中的地震可能发生在与三个阶梯脊相关的梯形断层段上。我们还提供了由生长的山脊抬升的湖泊沉积物的 U/Th 日期，约为 100 ka。根据累积的、过时的隆起和对地震序列引起的地表位移的了解，我们估计在过去的 100 ka 中发生了约 120 起此类事件，平均复发间隔为 830 年，Sefidabeh 逆冲断层的平均收敛率为 1.5 mm yr−1；无论哪种方式，每个估计都有两倍的不确定性。我们认为，Sefidabeh 断层最初是由许多小断层段合并而成，在过去 100 ka 中长度增长了约 2 cm yr−1。尽管在 SAR 干涉图中观察到的同震表面变形与折叠非常相似，但总体地形却并非如此，因为继承地形与早期地质变形相关。尽管如此，埋藏逆冲断层的活动可以很容易地通过其对地表排水的影响来检测：在解释不完全由当今变形造成的景观时，这是一个重要的教训。
In 1994, three shallow earthquakes of Mw∼ 6 occurred close together on blind thrusts near Sefidabeh in eastern Iran. In an earlier study of the teleseismic waveforms, the geomorphology and the faulting in the epicentral region, it was suggested that these earthquakes were associated with the growth of a ridge above a blind thrust fault system, whose activity could be detected by its effect on the surface drainage. In this study we present a SAR interferogram that precisely determines the location and amount of coseismic surface displacements, showing that the earthquakes in the Sefidabeh sequence probably occurred on en-echelon fault segments associated with three stepping ridges. We also present U/Th dates of ∼100 ka for lake deposits uplifted by the growing ridge. From the cumulative, dated uplift and knowledge of the surface displacements due to an earthquake sequence, we estimate that ∼120 such events have occurred in the past 100 ka, with an average recurrence interval of 830 yr, and an average convergence rate of 1.5 mm yr−1 on the Sefidabeh thrust; each estimate has an uncertainty of a factor of two, either way. We argue that the Sefidabeh fault originally formed by coalescence of many small fault segments, and has grown in length at about 2 cm yr−1 in the past 100 ka. Though the coseismic surface deformation observed in the SAR interferogram closely resembles folding, the overall topography does not, because of inherited topography associated with earlier geological deformation. In spite of this, the activity of the buried thrust fault can easily be detected by its effect on the surface drainage: a significant lesson when interpreting landscapes that are not entirely due to the present-day deformation.