The late quaternary slip rate and paleoearthquakes of the Cuopuhu section of the Litang-Yidun fault, western Sichuan
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摘要: 理塘—义敦断裂是川滇菱形块体内部一条延伸约130km的左旋走滑活动断裂,研究理塘—义敦断裂的构造活动历史有助于理解青藏高原物质向东逃逸—滑移场理论。将理塘—义敦断裂措普湖段作为研究对象,运用野外勘察、高精度测绘、探槽与14C测年等方法对措普湖段进行古地震探究。开挖2处探槽于冬欧山坡麓处,通过识别探槽内断裂与地层的切割关系,地层沉积特征,断层运动性质等标志,结合14C测年结果,共识别出4次古地震事件:事件Ⅰ发生于BC3382±60a之前;事件Ⅱ发生于BC3382±60a~BC1094±51a之间;事件Ⅲ与事件IV均发生于AD1330±44a之后。根据测绘断错地貌和末次冰期冰碛垄推算出晚更新世以来措普湖段平均滑动速率为4.15±0.5mm/a。Abstract: The Litang-Yidun fault is a left-hand strike-slip active fault that extends for about 130 km in the Sichuan-Yunnan rhombic block. Studying the tectonic activity history of the Litang-Yidun fault is helpful to understand the theory of material eastward escape-slip of the Qinghai-Tibet Plateau. In this paper, the Cuopuhu section of the Litang-Yidun fault is selected as the research object, and the paleo-seismic events of the Cuopuhu section are explored using methods such as field survey, trenching and 14C dating. Two exploration trenches were excavated at the foothills of Dongou mountain to identify the cutting relationship between faults, the strata, the sedimentary characteristics, the fault motion and other characteristics, combined with the 14C dating results, a total of 4 paleo-seismic events were identified. Event I occurred before BC3382±60a; Event II occurred between BC3382±60a~BC1094±51a; Event III and Event IV both occurred after AD1330±44a. According to the last glacial moraine ridge, the average slip rate of the Cuopuhu section since the Late Pleistocene is 4.15±0.5mm/a.
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Key words:
- active fault /
- Litang-Yidun fault /
- paleo-earthquake /
- slip rate /
- Cuopuhu /
- Eastern Tibetan Plateau
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