Comprehensive Multi-Level Exploration of Buried Active Faults： an Example of the Yinchuan Buried Active Fault     

Chai Chizhang 《中国地震研究》2007,21(3):225-235

The paper introduces the steps and methods of multi-approach,multi-level exploration of buried faults in thick Quaternary sediment regions by taking the test exploration of the Yinchuan active fault as example.Based on the comprehensive analyses of previous data,we choose the Xinqushao Village of Xingqing District of Yinchuan City as the test site for the comprehensive exploration.Firstly,we adopted shallow seismic investigation with group intervals of 10m,5m and 1m to gradually trace layer by layer the master fault of the Yinchuan buried fault from a deep depth to a shallow depth where drilling could be used.Then,with composite geological profile drilling,we determined the precise location and dip angle of the fault.The drilling show the buried depth of the upper offset point is 8.3m.Finally,large-scale trenching revealed that the actual buried depth of the upper offset point of the fault is 1.5m from the ground surface and there are paleoearthquake events of 5 stages.Combined with the preliminary result of corresponding sample age,we conclude the Yinchuan buried fault is a mid to late Holocene active fault.  相似文献   

Three-dimensional thermal structure of the Chinese continental crust and upper mantle   总被引：3，自引：0，他引：3  

An MeiJian  Shi YaoLin 《中国科学D辑(英文版)》2007,50(10):1441-1451

We invert S-wave velocities for the 3D upper-mantle temperatures, in which the position with a temperature crossing the 1300℃ adiabat is corresponding to the top of the seismic low velocity zone. The temperatures down to the depth of 80 km are then calculated by solving steady-state thermal conduction equation with the constraints of the inverted upper-mantle temperatures and the surface temperatures, and then surface heat flows are calculated from the crustal temperatures. The misfit between the calculated and observed surface heat flow is smaller than 20% for most regions. The result shows that, at a depth of 25 km, the crustal temperature of eastern China (500―600℃) is higher than that of western China (<500℃). At a depth of 100 km, temperatures beneath eastern and southeastern China are higher than the adiabatic temperature of 1300℃, while that beneath west China is lower. The Tarim craton and the Sichuan basin show generally low temperature. At a depth of 150 km, temperatures beneath south China, eastern Yangtze craton, North China craton and around the Qiangtang terrane are higher than the adiabatic temperature of 1300℃, but is the lowest beneath the Sichuan basin and the regions near the Indian-Eurasian collision zone. At a depth of 200 km, very low temperature occurs beneath the Qinghai-Tibet Plateau and the south to the Tarim craton.  相似文献   

瑞利散射激光雷达探测平流层和中间层低层大气温度   总被引：4，自引：0，他引：4       下载免费PDF全文

吴永华  胡欢陵  胡顺星  周军  张民 《大气科学》2002,26(1):23-29

介绍了一台瑞利散射激光雷达,它能够探测22～60 km范围内大气温度的垂直分布;比较了两种反演温度的数据处理方法.该激光雷达分别与UARS/HALOE卫星和无线电探空仪观测结果进行了对比,均表现了较好的一致性.同时还模拟分析了平流层低层气溶胶对计算温度的影响.  相似文献   

THE STUDY OF STORM RAINFALL CAUSED BY INTERACTION BETWEEN THE NON-ZONAL HIGH LEVEL JET STREAK AND TYPHOON IN THE DISTANCE   总被引：1，自引：1，他引：1  

丁治英  张兴强  何金海  徐海明 《热带气象学报(英文版)》2001,7(2):187-198

In this paper, statistics were analyzed concerning correlation between the storm rainfall far from typhoon and non-zonal upper-level jet stream. The results show that the jet stream at 200 hPa is constantly SW (90.2 %) during the period in which storm rainfall occurs. Rainfall area lies in the right rear regions of the jet axes. While the storm intensifies, the jet tends to be stronger and turn non-zonal. With the MM4 model, numerical simulation and diagnosis were carried out for Typhoon No.9711 (Winnie) on August 19 to 20, 1997. The distant storm rainfall is tightly correlative to the jet and low-level typhoon trough. The divergence field of jet is related to the v component. The upper level can cause the allobaric wind convergence at low level. This is the result of the form of low-level typhoon trough and the strength of the storm. By scale analysis, it is found that there is a branch of middle scale transverse inverse circulation in the right entrance regions behind the jet below the 300-hPa level, which is very important to the maintenance and strengthening of storm rainfall. This branch of inverse circulation is relative to the reinforcement of jet's non-zonal characteristics. From the field of mesoscale divergence field and non-zonal wind field, we know that the stronger symmetry caused by transverse circulation in the two sides of the jet, rainfall’s feedback and reinforcement of jet’s non-zonal characteristics had lead to positive feedback mechanism that was favorable of storm rainfall’s strengthening.  相似文献   

中国大陆及邻区上地幔各向异性研究   总被引：7，自引：0，他引：7       下载免费PDF全文

刘希强  周蕙兰  李红  季爱东 《地震学报》2001,23(4):337-348

为了深化对中国大陆及邻区上地幔介质形变强度和方向的空间变化图象、各向异性和剪切波分裂、各向异性以及应变、应变和构造过程关系的认识，我们以剪切波在分层各向异性介质中的传播理论为指导，以分裂剪切波观测为基础，借助数字化地震资料和高分辨率的信号处理技术，给出了对136次地震的分析结果，得到了20个台站下面的上地幔各向异性介质的变形强度和方向的空间变化图象；并结合已有研究结果，对中国大陆及邻区上地幔各向异性特性及其起源问题进行了讨论．   相似文献   

Seismic tomography shows that upwelling beneath Iceland is confined to the upper mantle   总被引：3，自引：0，他引：3  

G. R. Foulger  M. J. Pritchard  B. R. Julian  J. R. Evans  R. M. Allen  G. Nolet  W. J. Morgan  B. H. Bergsson  P. Erlendsson  S. Jakobsdottir  S. Ragnarsson  R. Stefansson  K. Vogfjörd 《Geophysical Journal International》2001,146(2):504-530

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Oceanic upper mantle structure from experimental scaling of V_S and density at different depths     

Mikhail K. Kaban  Peter Schwintzer 《Geophysical Journal International》2001,147(1):199-214

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Effects of vertical boundaries on infinite Prandtl number thermal convection   总被引：1，自引：0，他引：1  

Jun Korenaga  Thomas H. Jordan 《Geophysical Journal International》2001,147(3):639-659

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PGE geochemistry of Jiding ophiolite in Tibet and its constraint on mantle processes   总被引：3，自引：0，他引：3  

XIA Bin  CHEN Genwen  MEI Houjun  GUO Lingzhi  XIAO Xuchang  YU Hengxiang  QI Liang  WANG Guoqiang  Zhong Zhihong 《中国科学D辑(英文版)》2001,44(11):1019-1028

The total PGE amount (σPGE) of mantle peridotite in the Jiding ophiolite is slightly higher than that of the primitive mantle, but the PGE contents of basalt are higher than those of the mid-ocean ridge basalt (MORB), with obviously lower Pd/Ir ratios. The accumulates, dyke swarm and basalts show remarkable negative Pt and positive Rh anomalies, resulting in the special N-type PGE patterns. Mantle peridotite and crustal rocks have similar distribution patterns. It is proposed that the PGE distribution patterns in the Jiding ophiolite are closely related with a higher degree of partial melting of the mantle in this region. Magmatic crystallization-differentiation led to PGE fractionation, thus making the contents of PGE in the accumulates decrease in the ascending direction. The higher content of Au in the Jiding ophiolite is the result of metasomatic alteration at later stages. Pt-Pd fractionation indicates that both the PGEs are controlled by their alloy and sulfide phases. Positive Rh anomalies seem to be related with higher oxygen fugacity in the melts.  相似文献   

气旋爆发性发展过程的动力特征及能量学研究   总被引：19，自引：3，他引：19  

吕筱英  孙淑清 《大气科学》1996,20(1):90-100

本文对不同路径的爆发性气旋进行了动力特征及能量学研究。发现高空大值位涡空气的下伸是气旋爆发性发展的一个重要条件。初生气旋逐渐向强位涡区移近并形成上下位涡区相接的形势。使气旋迅速发展。高空急流与气旋发展有密切关系。发展中的气旋明显地向着急流左侧的辐散区移动。急流的突然加强及高空强风动量的不断下传，构成了下层的强风带及上下一致的急流结构。能量学研究指出在气旋发展前气旋内散度风动能向旋转风动能的转换突然增强。散度风动能在爆发气旋发展时有明显增长。  相似文献