Throughgoing crustal faults along the northern margin of the South China Sea and their role in crustal extension
Throughgoing crustal faults along the northern margin of the South China Sea and their role in crustal extension
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DOI：
10.1029/95jb01867
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发表时间：
1995-11
影响因子：
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通讯作者：
D. Hayes;S. Nissen;P. Buhl;J. Diebold;Yao Bochu;W. Zeng;Yong-shun Chen
中科院分区：
文献类型：
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作者：
D. Hayes;S. Nissen;P. Buhl;J. Diebold;Yao Bochu;W. Zeng;Yong-shun Chen
根据新的单船和双船多通道地震资料，对南海北部边缘进行了研究，发现存在贯穿整个地壳的高反射、陡倾正断层。这些断层倾角为~ 25°-40°，与局部地壳减薄~ 5-15公里有关，代表了数十公里的水平延伸。沿个别断层测得的水平延伸范围为~ 5-20公里。虽然这些断层所占的水平伸展的相对量与整个边缘的伸展量相比是适度的（只有大约15%或更少），但沿着这些断层表面发生的局部地壳减薄的量是相当显著的。在一个断层位置，地壳厚度减少了约40%。尽管所描述的断层是在沿断层边缘的三个不同位置发现的，但它们的走向似乎各不相同。在两个例子中，断层与推断的大致南北伸展方向相倾斜。考虑到这一特征，再加上一些地壳断层似乎是地壳厚度和下地壳反射率不同的广阔区域之间的突然边界，这表明至少其中一些断层在裂谷作用之前就存在了。这些断层被认为是以前的逆冲断层，可能与三叠纪缝合带和/或白垩纪俯冲边缘有关，在随后的裂谷作用中被重新激活为正断层。另外，一些贯穿断层可能代表最初由于地壳伸展的简单剪切反应而形成的地壳剥离面。
A study of the rifled northern margin of the South China Sea, based on new single-ship and two-ship multichannel seismic data, has revealed the presence of highly reflective, steeply dipping normal faults which cut through the entire crust. These faults, with dips of ∼25°–40°, are associated with localized crustal thinning of ∼5–15 km and represent horizontal extension of the order of tens of kilometers. A range of ∼5–20 km of horizontal extension has been measured along individual faults. Although the relative amount of horizontal extension taken up by these faults is modest compared to the total extension across the margin (only about 15% or less), the amount of localized crustal thinning which takes place along these fault surfaces is quite significant. At one fault location, the crustal thickness is reduced by ∼40%. Although the faults described have been recognized at three separate locations along the margin, their trends appear to differ at each. In two examples, the faults are oblique to the inferred, general north-south extension direction of the margin. This characteristic, taken with the fact that some of the crustal faults also appear to serve as abrupt boundaries between broad regions of differing crustal thickness and reflectivity of the lower crust, suggests that at least some of these faults were present prior to rifting. Such faults are postulated to have been former thrust faults, perhaps associated with a Triassic suture zone and/or Cretaceous subduction margin, which have been reactivated as normal faults during subsequent rifting. Alternatively, some of the throughgoing faults may represent crustal detachment surfaces that first formed as the result of a simple shear response to crustal extension.