Large river offsets and Plio‐Quaternary dextral slip rate on the Red River fault (Yunnan, China)
Large river offsets and Plio‐Quaternary dextral slip rate on the Red River fault (Yunnan, China)
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DOI：
10.1029/2000jb900135
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发表时间：
2001-01
影响因子：
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通讯作者：
A. Replumaz;R. Lacassin;P. Tapponnier;P. Leloup
中科院分区：
文献类型：
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作者：
A. Replumaz;R. Lacassin;P. Tapponnier;P. Leloup
利用多光谱SPOT影像和1/100，000地形数据，我们提出了一个改进的地图活动红河断裂带之间的弥渡（中国云南）和河内（越南）。该断裂带由多条平行线组成，其中之一的元江断裂以前未被发现。也似乎有一个组成部分的伸展所有沿着断裂带。这种伸展从云南到南海沿岸向东南方向增加，描述华南相对于印度支那运动的矢量在N45°-135 ° E象限内。我们试图通过恢复大的河流偏移量和寻找最大的，合理的一个来评估红河断层（RRF）的上新世-第四纪右旋滑动速率。在云南大部分地区，该断层垂直于排入红河的当地集水区。从SPOT卫星图像和1/100，000地形图上精确绘制的河道图中，可以检测和重建沿断层沿着的许多多重偏移。明显的偏移量和断层上游河流长度之间缺乏相关性，这表明，要么是在沿着断层发生右旋滑动之前就已建立了大部分排水系统，要么是发生了频繁的捕获。因此，我们试图通过逐步恢复右旋位移，以500 m的增量，最多偏移50 km，来找到断层上游和下游一系列河道之间的最佳拟合。对于每个增量，我们测量上游和下游通道之间的失配（均方根，RMS）。最佳拟合和最小RMS获得的偏移量为25±0.5 km，我们解释为代表最清晰，大的右侧位移记录在地貌沿着活动红河故障。由于右旋运动很可能在500万年左右开始，断层上上新世-第四纪最可能的平均滑动速率为5 mm/年。我们将断层上一大片区域明显缺乏地震活动归因于大地震之间的千年复发时间。我们的研究表明，相对较小的排水系统可以很好地记录相当大的累积断层偏移。
Using multispectral SPOT images and 1/100,000 topographic data, we present an improved map of the active Red River fault zone between Midu (Yunnan, China) and Hanoi (Vietnam). The fault zone is composed of parallel strands, one of which, the Yuanjiang fault was previously undetected. There also appears to be a component of extension all along the fault zone. Such extension increases toward the SE, from Yunnan to the south China sea coast, and the vector describing the motion of south China relative to Indochina points within the N45°–135°E quadrant. We attempt to assess the Plio-Quaternary dextral slip rate on the Red River fault (RRF) by restoring large river offsets and searching for the largest, plausible one. Across much of Yunnan, the fault is perpendicular to local catchments that drain into the Red River. From precise mapping of the river courses on SPOT satellite images and on 1/100,000 topographic maps, numerous multiple offsets along the fault can be detected and reconstructed. The lack of correlation between the apparent offsets and the lengths of the rivers upstream from the fault suggests either that the drainage system was in large part established prior to the onset of dextral slip along the fault or that frequent captures have occurred. We thus try to find the best fit between series of river channels upstream and downstream from the fault by progressively restoring the dextral displacement in increments of 500 m, up to an offset of 50 km. For each increment we measure the misfits (root mean squares, RMS) between the upstream and downstream channels. The best fit and smallest RMS are obtained for an offset of 25±0.5 km that we interpret to represent the clearest, large right-lateral displacement recorded in the geomorphology along the active Red River fault. Since dextral motion is likely to have started around 5 Myr, the most probable average Plio-Quaternary slip rate on the fault is of order of 5 mm/yr. We attribute the apparent lack of seismic activity on a large stretch of the fault to millennial recurrence times between great earthquakes. Our study shows that relatively small drainage systems can keep a good record of fairly large cumulative fault offsets.