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A study on the evolutionary process of a large-scale strike-slip fault

大型走滑断裂演化过程研究

基本信息

批准号：
18500776
负责人：
IKEDA Yasutaka
金额：
$ 2.59万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18500776/
关键词：
active fault Tibetan Plateau strike-slip fault international cooperative research China

项目摘要

The evolutionary process of a fault includes several stages, starting from a set of fractures in intact rocks, through a somewhat integrated zone of fractures and minor faults, finally to a single strand of matured fault. This process has been studied by comparing different faults at different evolutionary. Because the faults used in these studies have different tectonic setting, it was difficult to differentiate the evolutionary process from variation in tectonic setting. In this study, we tried to clarify the process through a study of the Kanding-Xianshuihe-Xiaojiang Fault Zone (KXXFZ) in southeastern Tibetan Plateau.A big bend exists in the middle portion of this fault zone. The Dalianshan Fault Zone (DFZ) develops east of, and shortcutting, this big bend. We made precise mapping and field observations of tectonic landforms. The following results were obtained:1. The total amount of slip on DFZ is found to be 3-7 km, which is one order of magnitude smaller than that on KXXFZ. The slip rate on DFZ in Holocene time is estimated at 4 mm/yr or more. These imply that the initiation of DFZ is younger than 1-2 Ma, which again is one order of magnitude younger than KXXFZ.2. The DFZ consists of many fault strands that are arranged en echelon ; the sheared zone of each fault strand is much narrower than that associated with the main fault zone. This, coupled with the above observations, indicates that the Dalianshan Fault Zone is at the juvenile stage of a fault with less integrated fault strands.3. The DFZ develop in a Precambrian platform without any signs of inheritance from preexisting structures. It is therefore inferred that, in association with the formation of a big bend, a new fault was created in intact continental crust in recent geologic time, shortcutting the big bend.

断层的演化过程包括几个阶段，从完整岩石中的一组断裂开始，经过断裂和小断层的某种整合带，最后到一条成熟断层。通过对比不同演化阶段的断层，研究了这一过程。由于所研究的断层具有不同的构造背景，很难区分其演化过程和构造背景的变化。本文通过对青藏高原东南部康定-鲜水河-小江断裂带的研究，试图阐明这一过程。大连山断裂带在这个大弯的东面发育，并缩短了这个大弯.我们对构造地貌进行了精确的测绘和实地观察。获得了以下结果：1. DFZ上的总滑移量为3-7 km，比KXXFZ上的滑移量小一个数量级。全新世DFZ上的滑动速率估计为4 mm/yr或更大。这意味着DFZ的起始时间小于1-2 Ma，比KXXFZ年轻一个数量级。DFZ由许多断层链组成，这些断层链呈雁列排列;每个断层链的剪切带比与主断层带相关的剪切带窄得多。结合上述观测结果，表明大连山断裂带正处于断裂的幼年阶段，断裂带的完整性较差. DFZ在前寒武纪地台中发育，没有任何继承先前存在结构的迹象。因此，可以推断，与大弯的形成有关，在现代地质时期，在完整的陆壳中产生了一条新的断层，缩短了大弯。