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位于南北地震带南段的云南地区是中国大陆内部地震活动最强的地区之一,近年来该区地震活动频繁,展开对该区的探测与研究对人们认识地震孕震背景及板块相互运动具有重要意义.在中国地震局“中国地震科学台阵探测——南北地震带南段”行业专项的支持下,2011年底中国地震局地球物理勘探中心在滇南沿镇康—泸西一线布设一条近东西向的深地震宽角反射/折射探测剖面.该探测剖面跨越三江褶皱系、扬子地台、华南地块等多个地质构造单元,同时穿越南汀河断裂、澜沧江断裂、红河断裂带、小江断裂带等多个重要断裂带.探测剖面长600km,沿线共布设11个炮点和400余台三分量地震数字仪进行爆破和接收.本文利用有限差分和时间项方法对沿线11炮初至波资料进行了计算处理,获取了探测剖面的基底速度结构.研究结果表明:沿线不同地质构造单元基底界面形态起伏变化剧烈,其深度在1.0~7.0km范围内变化,速度横向不均匀性明显.在测线西端地表速度约4.6km·s-1,基底深度较浅,起伏变化不大;地表速度在三江褶皱系下降至4.3km·s-1,而基底埋深达7.0km左右.在扬子地台基底埋深有一个缓慢的变浅,基底深度约5.0km,地表速度约4.5km·s-1.测线在东端进入华南块体,基底深度迅速变浅,甚至出露于地表,地表速度增至约5.2km·s-1.在速度等值线变化剧烈的地方与该区分布的断裂带有很好的对应关系,尤其是在红河断裂带两侧速度等值线及界面形态变化剧烈,该特征在首波的记录截面图上也能清晰的体现.本结果为进一步研究该区强震发生背景及深部动力学意义提供了重要的科学依据.
The Yunnan area located in the southern segment of the North-South Seismic Belt is one of the areas with the highest seismic activity in mainland China. In recent years, the area has been characterized by frequent earthquakes and exploration and research on this area. It is of great significance for people to understand the earthquake seismogenic background and the reciprocal movement of the plate Important meaning.Under the support of China Earthquake Administration “China Earthquake Science Array Detector - South-North Seismic Belt South ” industry specifics, by the end of 2011 China Earthquake Administration Geophysical Exploration Center in Southern Yunnan along the town Kang - Luxi layout A near-to-deep deep seismic wide-angle reflection / refraction detection profile that spans a number of geological tectonic units such as the Sanjiang fold system, the Yangtze platform and the South China block, passes through the Nantinghe fault, the Lancangjiang fault, the Honghe fault zone , Xiaojiang fault zone, etc. The detection profile is 600km long, with 11 shots and more than 400 three-component seismographs along the line for blasting and receiving.In this paper, finite difference method To-wave data were calculated and processed to obtain the basement velocity structure of the exploration profile.The results show that: along the line of different geological formations basement interface morphology The depth of which varies in the range of 1.0-7.0km, and the horizontal heterogeneity of velocity is obvious.When the surface velocity is about 4.6km · s-1 at the west end of the line, the depth of basement is shallow and the undulation does not change much. The fold decreases to 4.3 km · s-1, while the depth of the basement reaches about 7.0 km. The basement depth of the Yangtze platform decreases slowly with a depth of about 5.0 km and a surface velocity of about 4.5 km · s-1. The line entered the South China block at the east end, and the depth of the basement rapidly became shallow and even exposed to the surface. The surface velocity increased to about 5.2km · s-1. Where the velocity contour changed drastically, This feature is clearly reflected in the recorded cross-section of the first wave.This result is very useful for further study of the strong earthquakes in the area Occurrence of background and deep kinetic significance provides an important scientific basis.