小江断裂带南段全新世活动的地质地貌证据与滑动速率

发布时间：2018-11-11 11:04

【摘要】：小江断裂带南段位于近SN向的鲜水河-小江断裂系与NW向的红河-哀牢山断裂系的交会地带。在遥感影像上,小江断裂带南段线状特征清楚,且连续分布,表现为1条贯通的、单一的断裂构造,全长约70km,总体走向N20°E左右,中间呈略向E凸出的弧形。在龙潭村两岔河一带,沿着该断裂段存在比较典型的山脊、冲沟同步左旋位错现象。在跨断塞塘开挖的探槽剖面上,断裂分布状况、断错地层的沉积学特征、产状变化以及初步年代测试结果揭示了3次明显断错地表的古地震事件,显示了小江断裂带南段具有重复孕育和发生强震的能力。利用Trimble 5800 GPS实时差分测量系统,对两岔河地区存在典型同步位错特征的2条冲沟及其它们中间的台地进行了精细测量,位错量为(18.3±0.5)m;T_2阶地面是断裂西盘2条冲沟之间及其邻近地带的最高层状地貌面,通过不同深度年代数据的线性回归分析,该地貌面停止接受沉积的时代约为2606a BP。根据地质方法获得了小江断裂带南段全新世左旋走滑速率为(7.02±0.20)mm/a,与利用GPS数据获得的结果有着较好的一致性。对小江断裂带南段活动性和滑动速率的初步研究结果表明,在滇东南地区不存在川滇块体向S或SSE方向滑移被曲江断裂和石屏-建水断裂挤压变形吸收、而使得小江断裂带南段左旋走滑速率大幅度减小的现象,该断裂段是1条活动性明显的全新世断裂。这些初步认识为小江断裂带南段的未来地震危险性评价以及川滇地区的地震构造模型建立和检验提供了可以借鉴的基础地质资料。
[Abstract]:The southern section of the Xiaojiang fault zone is located in the intersection zone between the Xianshuihe-Xiaojiang fault system near the SN direction and the Honghe-Ailaoshan fault system in the NW direction. In remote sensing images, the southern section of the Xiaojiang fault zone has clear linear features and continuous distribution, showing a single fault structure with a total length of about 70 km, with an overall strike of about N20 掳E, and a slightly protruding arc in the middle. Along the Liangcha River of Longtan Village, there are typical ridges along this fault section and synchronous left-lateral dislocation phenomenon in gullies. The distribution of faults, the sedimentary characteristics of faulted strata, the changes of occurrence and the preliminary dating results reveal three paleoearthquake events on the surface of obvious fault on the section of the exploration channel excavated across the faulted seawall. It shows that the south section of Xiaojiang fault zone has the ability of repeated preparation and strong earthquake. Using Trimble 5800 GPS real time differential measurement system, two gullies with typical synchronous dislocation characteristics and other platforms in the middle of Liangchahe area were carefully measured. The dislocation amount was (18.3 卤0.5) m. The T _ 2th surface is the highest stratified geomorphologic surface between the two gullies in the western rim of the fault and its adjacent zone. By linear regression analysis of the age data of different depths, the age at which the geomorphologic surface ceased to accept deposition was about 2606a BP.. According to the geological method, the left-lateral strike-slip rate of the southern section of the Xiaojiang fault zone in Holocene is (7.02 卤0.20) mm/a, which is in good agreement with the results obtained from the GPS data. The preliminary study on the activity and slip rate of the southern section of the Xiaojiang fault zone shows that there is no S or SSE direction slip of the Sichuan-Yunnan block in the southeast of Yunnan province, which is absorbed by the compression deformation of Qujiang fault and Shiping-Jianshui fault. However, the left-lateral strike-slip rate of the southern section of the Xiaojiang fault zone is greatly reduced. The fault segment is an active Holocene fault. These preliminary understandings provide basic geological data for the future seismic risk assessment in the southern section of the Xiaojiang fault zone and for the establishment and verification of seismic structural models in Sichuan-Yunnan region.
【作者单位】：中国地震局地质研究所;中国地质大学(北京) 地球科学与资源学院;陕西省地震局;
【基金】：国家自然科学基金(41372219) 地震行业科研专项(201108001)共同资助
【分类号】：P315.2

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