Application of trishear fault-propagation folding to active reverse faults: examples from the Dalong Fault, Gansu Province, NW China
Application of trishear fault-propagation folding to active reverse faults: examples from the Dalong Fault, Gansu Province, NW China
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DOI：
10.1016/j.jsg.2005.10.006
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发表时间：
2006-02
影响因子：
3.1
通讯作者：
R. Gold;E. Cowgill;Xiao-feng Wang;Xuanhua Chen
中科院分区：
文献类型：
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作者：
R. Gold;E. Cowgill;Xiao-feng Wang;Xuanhua Chen
确定准确的断层滑动速率在1 ka至1 Ma的时间尺度需要良好的约束palmostastic重建可定年的地貌和/或地质标志。虽然一般的运动学模型已被开发，以同时重建基岩（如层理和断层产状）和新构造标志（如斯特拉特阶地）沿沿着活跃的走滑和逆冲断层，目前尚不清楚这些模型是否也可以解释变形沿沿着陡倾角（>45°）逆断层。为了解决这个问题，我们调查了活动的，倾角为150 °的大隆逆断层系统。该断裂系统长约40 km，是中国西北阿尔金断裂带活动的一部分，该断裂带沿着阿克塞限制步距。我们的几何和运动学分析表明，传统的断层弯曲褶皱模型不能满足我们观察到的基岩记录中的陡倾角断层几何形状。同样，标准的断层传播褶皱模型也无法与我们对一组河流阶地的测量结果相匹配。然而，通过扩展断层传播褶皱的三剪模型来跟踪基岩和新构造标志，我们能够匹配这两组记录。特别是，我们已经开发了三剪切运动学模型的两个网站（刘陈子和青崖子）使用的数值模拟程序，断层/褶皱V.5.0。这一工作表明，活动性三剪断层传播褶皱的一个重要含义是阶地变形在断层迹两侧延伸超过1 km。因此，为了精确测量上盘和下盘中匹配阶地之间的垂直分离的总量，横跨活动逆断层的阶地剖面必须在该变形带的两侧延伸1-2km。
Determining accurate fault slip rates at 1ka to 1Ma timescales requires well-constrained palinspastic reconstructions of dateable geomorphic and/or geologic markers. Although general kinematic models have been developed to simultaneously reconstruct both bedrock (e.g. bedding and fault attitudes) and neotectonic markers (e.g. strath terraces) along active strike-slip and thrust faults, it is not clear if these models can also account for deformation along steeply dipping (>45°) reverse faults. To address this problem, we have investigated the active, ∼50° dipping, Dalong reverse fault system. This ∼40-km-long fault system forms part of the Aksai restraining stepover along the active, left-slip Altyn Tagh Fault in northwestern China. Our geometric and kinematic analyses show that conventional fault-bend fold models cannot satisfy the steeply-dipping fault geometry we observe in the bedrock record. Likewise, standard fault-propagation fold models fail to match our measurements of a set of fluvial terraces. However, by expanding the trishear model of fault-propagation folding to track both bedrock and neotectonic markers, we are able to match both sets of records. In particular, we have developed trishear kinematic models for two sites (Liuchenzi and Qingyazi) using the numerical modeling program, Fault/Fold v.5.0. This work indicates that an important implication of active trishear fault-propagation folding is that terrace deformation extends for over 1km on either side of the fault trace. Thus, to accurately measure the total magnitude of vertical separation between matching terraces in the hanging wall and footwall, terrace profiles across active reverse faults must extend 1–2km on either side of this zone of deformation.