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31.
Crustal structure beneath the Songpan—Garze orogenic belt 总被引:2,自引:0,他引:2
The Benzilan-Tangke deepseismic sounding profile in the western Sichuan region passes through the Song-pan-Garze orogenic belt with trend of NNE.Based on the travel times and the related amplitudes of phases in the record sections,the 2-D P-wave crustal structure was ascertained in this paper.The velocity structure has quite strong lateral variation along the profile.The crust is divided into 5layers,where the first,second and third layer belong to the upper crust,the forth and fifth layer belong to the lower crust.The low velocity anomaly zone gener-ally exists in the central part of the upper crust on the profile,and it integrates into the overlying low velocity basement in the area to the north of Ma‘erkang.The crustal structure in the section can be divided into 4parts:in the south of Garze-litang fault,between Garze-Litang fault and Xianshuihe fault,between Xianshuihe fault and Longriba fault and in the north of Longriba fault,which are basically coincided with the regional tectonics division.The crustal thickness decreases from southwest to northeast along the profile,that is ,from62km in the region of the Jinshajiang River to 52km in the region of the Yellow River.The Moho discontinuity does not obviously change across the Xianshuihe fault basesd on the PmP phase analysis.The crustal average velocity along the profile is lower,about 6.30 km/s.The Benzilan-Tangke profile reveals that the crust in the study area is orogenic.The Xianshuihe fault belt is located in the central part of the profile,and the velocity is positive anomaly on the upper crust,and negative anomaly on the lower crust and upper mantle.It is considered as a deep tectonhic setting in favor of strong earthquake‘s accumulation and occurrence. 相似文献
32.
Using methods of discontinuous deformation analysis and finite element (DDA+FEM), this paper simulates dynamic processes of the Tangshan earthquake of 1976, which occurred in the northern North China where its internal blocks apparently interacted. Studies focus upon both the movement and deformation of the blocks, in particular, the Ordos block, and variations of stress states on the boundary faults. The Tangshan earthquake was composed of three events: slipping motions of NNE-striking major fault, NE-striking fault near the northeastern end of the NNE-striking fault, and NW-striking fault on the southeastern side of the NNE-striking fault. Compared with previous studies, our model yields a result that is more agreeable with the configuration of aftershock distributions. A number of data are presented, such as the principle stress field during the earthquake, contours of the maximum shear stress, the strike-slip deformation between blocks near the earthquake focus, time-dependent variations of slips of earthquake-triggered faulting, the maximum slip distance, and stress drops. These results are in accord with the earthquake source mechanism, basic parameters from earthquake wave study, macro-isoseismic line, observed horizontal displacement vectors, etc. The Tangshan earthquake exerted different influences on the adjacent blocks and boundary faults between them, thus resulting in differential movement and deformation. The Ordos block seems to have experienced the small-scale counterclockwise rotation and deformation, but its northeast part, bounded on the east by the Taihangshan and on the north by the Yanshan and Yinshan belts, underwent relatively stronger deformation. The Tangshan earthquake also changed the stress state of boundary faults of the North China, leading to an increase in shear stress and a decrease in normal stress in the NW-trending Zhangjiakou-Penglai fault through Tangshan City and the northern border faults of the Ordos block, and therefore raises the potential risk of earthquake occurrence. This result is supported by the facts that a series of Ms ≥ 6 earthquakes took place at the northern margin of the Ordos block after the Tangshan earthquake. 相似文献
33.
本文主要根据水泉湾泉和李家庄泉泉域的地质和水文地质资料,分析了本区内岩溶的发育特征和岩溶地下水的循环规律.研究分析了水泉湾泉和李家庄泉的形成原因。 相似文献
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35.
应用单多普勒雷达资料反演风场作暴雨中尺度分析 总被引:7,自引:2,他引:7
针对2002年6月23日发生在安徽西部的一次暴雨过程,以有限的探空资料作为大尺度背景场,应用合肥CINRAD-98D多普勒雷达资料,通过准四维变分分析方法进行反演,获得了不易被常规探测到的中小尺度三维风场,由此分析了引起强降水的中尺度天气系统。指出暴雨中心位于风速切变的下方,同时上空也伴随辐合中心,以及正涡度极大值。分析结果表明,变分法是一种较为准确的从雷达资料中提取三维风场的方法。利用雷达资料反映中尺度天气系统,同时又加入大尺度的背景场作为基础,两者相互弥补,能较真实地反映实际天气状况。在气象预报中有效地应用多普勒雷达资料,有助于研究更为细致的中小尺度天气系统结构,而且也可为中小尺度数值预报模式提供准确的初始场。 相似文献
36.
位于川西地区的奔子栏——唐克深地震测深剖面以NNE走向穿越松潘——甘孜造山带.根据人工地震记录分析得到的震相走时和相关的振幅信息,确定了该剖面二维P波地壳速度结构.剖面的地壳结构可分为5层,其中第1,2,3层为上地壳;第4,5层为下地壳.上地壳中部普遍存在低速异常带,但龙日坝以北,这一低速带与其上覆的低速基底合为一体.同时,沿剖面的地壳速度结构具有较强的横向变化.据此,可将剖面分为4段,即甘孜——理塘断裂以南、甘孜——理塘断裂至鲜水河断裂、鲜水河断裂至龙日坝断裂和龙日坝断裂以北. 这与区域构造划分基本一致. 地壳厚度沿测线从南西向北东逐渐减薄,即从金沙江畔的62 km减小到黄河附近的52 km. 根据PmP震相分析,莫霍界面深度在鲜水河断裂两侧没有明显变化.全剖面的地壳平均速度较低,为6.30 km/s.奔子栏——唐克剖面揭示了该地区的造山带型地壳上地幔结构特征.鲜水河断裂带位于剖面的中部,该地区的上地壳速度为正异常,而下地壳和上地幔顶部存在负异常.笔者认为,这是一类有利于强震孕育和发生的深部构造环境. 相似文献
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38.
本文叙述了S系列双频道数字激电仪在使用中常遇到的问题及易发生的故障,提供了排除方法。 相似文献
39.
Zheng Feili Tang Keli Zhang Keli Cha Xuan Bai Hongying Northwest Institute of Soil Water Conservation CAS Ministry of Water Resources Yangling Shaanxi People''s Republic of China 《地理学报(英文版)》1997,(2)
Forlongtime,theproblemaboutnaturalerosionandartificiallyacceleratederosionisindispute.HistoricalgeographersconsiderthathumaninducedecoenvironmentaldestructionisaccountablefortheseveresoilerosionandecoenvironmentdeteriorationonLoessPlateau[7,8].Somegeolog… 相似文献
40.
采用调速稳速集成电路通过电位调节买现自反馈电子稳速,克服了实验过程中溶液阻尼变化对电机转速的影响,并利用高精度时钟信号与十进制记数器完成光电测速过程。 相似文献