李文巧1,
苏鹏2,
梁朋3
1. 中国地震局地震预测研究所, 地震预测重点实验室, 北京 100036
2. 中国地震局地质研究所, 北京 100029
3. 中国科学院地理科学与资源研究所, 北京 100101
基金项目: 中国地震局地震预测研究所基本科研业务费专项项目（批准号：2017IES010105、2013IES010101和2014IES010104）资助
详细信息
作者简介: 王林, 男, 35岁, 副研究员, 构造地质学专业, E-mail:2609759749@qq.com
中图分类号: P542;P931.1 收稿日期:2017-07-30
修回日期:2017-11-15
刊出日期:2018-01-30
Tectonic response of the river and layered landform surface in the Lushan Basin and its implication
Wang Lin1,,Li Wenqiao1,
Su Peng2,
Liang Peng3
1. Key Laboratory of Earthquake Prediction, Institute of Earthquake Forecasting, China Earthquake Administration, Beijing 100036
2. Institute of Geology, China Earthquake Administration, Beijing 100029
3. Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101
MSC: P542;P931.1
--> Received Date: 30 July 2017
Revised Date: 15 November 2017
Publish Date: 30 January 2018
摘要
摘要:基于芦山盆地之内的天全河（R1）、老场河（R2）、灵关河（R3）、西川河（R4）、沫河（R5）这5条横穿芦山地震震区河流的水系及相关层状地貌面的构造响应，反演了芦山盆地山前逆冲断层的构造运动。基于Google Earth影像、国产高分卫星数据（GF2）以及SRTM-30 m的DEM地形数据，首先对水系及层状地貌面进行了遥感解译和野外考察验证，然后基于GIS平台的构建多重缓冲区、生成离散化点集以及空间投影等主要技术方法最终生成了能够反映出水系河床、层状地貌面顺河同步地形变化的综合剖面，并利用野外差分GPS实测验证了剖面图结果的准确性。综合剖面揭示出芦山盆地内的河流两侧普遍发育了5级层状地貌面，而且水系河床上主要发育着两类构造成因的裂点，第一类裂点主要沿着芦山向斜西北翼边缘的走向分布，是由于向斜西北翼相对于向斜核部的整体抬升而形成的，而第二类裂点主要在芦山向斜内部分布，是由于芦山向斜内次级活动褶皱的逆冲运动而形成的。芦山盆地内的构造裂点对层状地貌面的空间分布具有"割裂"效应，不同宽谷洼地之内的层状地貌面往往以构造裂点为界各自独立地分布。随着双石-大川断裂对芦山向斜推挤作用的增强，芦山向斜从西南部的复式向斜转变为东北部的单式向斜并直至最终尖灭，并有可能形成了一条盲逆断层，而芦山地震的发震构造应该与之密切相关。
关键词: 芦山向斜/
水系/
层状地貌面/
裂点/
构造响应/
山前断裂/
活动褶皱/
发震构造
Abstract:The seismogenic tectonic of the Lushan erathquake is still uncertain until now. The front of the enveloping line of the Lushan earthquake aftershocks has broken away from the main range-front fault and extended into the Lushan basin, and therefore the seismogenic fault of the Lushan earthquake may belong to the piedmont thrust fault system, but it need more evidence to prove this viewpoint further. There are 5 rivers in the Lushan basin which flow across the Lushan basin and the Lushan earthquake zone, namely the Tianquan River (R1), the Laochang River (R2), the Lingguan River (R3), the Xichuan River (R4)and the Mohe River (R5). In this paper, based on the tectonic response of the drainage and layered landform surface on these rivers, we make an inversion study of the tectonic movement of the piedmont thrust fault in the Lushan basin, and try to find out the active tectonic or fault corresponding to the distribution of the Lushan earthquake aftershocks, so we can explore the seismogenic tectonic of the Lushan earthquake.
Based on Google Earth online image and domestic high resolution satellite image (GF2), firstly, we make a detailed and accurate interpretation of the 5 levels of layered landform surfaces along both sides of each river by means of remote sensing interpretation and field geological investigation, namely the first level of alluvial terrace (T1), the second level of alluvial terrace (T2), the third level of proluvial terrace (S3), the fourth level of fluvioglacial terrace (S4)and the fifth level of fluvioglacial terrace (S5). Then, based on SRTM-30 m DEM data and the powerful function of the GIS platform, we establish the multiple buffer zones, generate the discrete point sets, make the spatial projection and finally obtain an integrated topographic profile, and this kind of integrated topographic profile can reflect the synchronous topographic variation along the river flow direction of the river bed and every level of the layered landform surface at the same time, and we test and verify the accuracy of the profile through differential GPS field measurement. On one hand, this kind of integrated profile can reflect the distribution along the river of the 5 levels of layered landform surface above clearly, while on the other hand, it can also reveal various and specific forms of tectonic response of the drainage and the layered landform surface intuitively, and this method can be token as an simple and effective way of the analysis of the regional landform surfaces.
Through the analysis of the integrated topographic profile above, we find that there exist 2 kinds of knick point on the riverbed of every river due to tectonic factor. The first kind of knick point is located along trend of the NW limb border of the Lushan syncline which is caused by the overall uplifting of the NW limb relative to the syncline nucleus. Specifically, Shuangshi-Dachuan Fault (SDF)is a Holocene fault with weak activity which continually thrust toward the Lushan basin, and the NW limb of the Lushan syncline adjoining the SDF uplift gradually due to the lateral compression of the SDF accordingly, and this uplifting caused the formation of the first kind of knick point along the NW limb trend.The second kind of knick point is located within the Lushan basin which is caused by the thrusting of the secondary fold in the Lushan basin. Specifically, an secondary active anticline thrust upwards along the Shiyang Fault which has broken onto the ground suface, and the top of the anticline nucleus uplift accordingly, and this uplifting caused the formation of the second kind of knick point on the top of the nucleus.
The second kind of knick point usually separate the layered landform surface on the river into different segments, causing the alternative distribution of the deeply-incised canyon and the broad-valley depression along the river. Every level of layered landform surface along the same river are all cut into two independent segment by this kind of knick point, and each river segment between the knick point looks like a small depression with broad valley, and the alluvial material, the proluvial material and the fluvioglacial material all deposit in this valley because of the local stable sedimentary environment and depressed terrain, and finally the layered landform surface formed in this depression between the knick point. The terrain of the river segment near the knick point mainly comprise of steep deeply-incised valley which is unfavorable for the deposition and is hard to keep enough material to form the layered landform surface of a certain scale.
The whole Lushan syncline is subjected to the lateral compression by the SDF and thus deforms, and meanwhile a series of secondary active fold form accordingly in the Lushan syncline. Due to the strength difference of the compression by the SDF, these secondary folds evolve in different ways. In the southwest part of the Lushan basin, the compression is week, and several secondary folds and fault develop within the broad composite Lushan syncline, and the fault has broken onto the ground surface. While in the northeast of the Lushan basin, the compression is much stronger, and the broad composite Lushan syncline has transformed into a single syncline which totally disappears towards northeast, and the fault has no longer broken onto the ground surface which may has evolved into an blind thrust F'. If fault F' really exists, then it should be closely related to the seismogenic tectonic of the Lushan earthquake.
Key words:Lushan basin/
river system/
layered landform surface/
knick point/
tectonic response/
piedmont thrust fault/
active fold/
seismogenic tectonic
PDF全文下载地址:
http://www.dsjyj.com.cn/data/article/export-pdf?id=dsjyj_11439
