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81.
沈阳2×200兆瓦低温核供热站厂址基准地面运动参数的确定   总被引:2,自引:0,他引:2  
本文在综合厂址、近区域及区域地震地质资料的基础上,根据有关规范的要求,采用地震构造法、最大历史地震法和概率法分别计算了沈阳2×200兆瓦低温核供热站厂址的极限安全地震动SL-2,计算结果分别为200Gal、125Gal和170Gal。取三者最大值,厂址SL-2应当是200gal。厂址基岩地面运动SL-2水平向加速度反应谱取确定性法和概率法计算曲线的外包线作为用于厂址的基岩加速度反应谱。  相似文献   
82.
强震观测建筑结构的地震反应分析   总被引:5,自引:0,他引:5  
选择取得强震观测资料的建筑结构为研究对象,采用有限元法建立结构的动力反应分析模型,利用SAP2000程序分析了结构的地震反应,并同实际记录到的结构地震反应进行了对比分析,讨论了结构模型参数估计和一些不确定因素对模型精度的影响。  相似文献   
83.
利用常规天气图、物理量诊断分析、逐时红外云图、单站资料等,对2003年4月12日影响鹰潭市的强对流、暴雨天气过程进行分析,认为该过程是在一定的大尺度环流背景下,由不同层次的天气系统共同作用下产生的;其触发机制是冷空气从近地层楔入暖空气中,在高、低空急流、层结不稳定等诸多有利条件下,由几个小尺度对流云团合并发展成1个中尺度对流复合体(MCC).  相似文献   
84.
1 INTRODUCTION Most of the conventional sea surface wind data are measurements from ships, buoys and islands, with coverage and spatial resolution far below the requirements of research and application. At present, due to limited understanding of physical processes and efficient exploitation of data, numerical prediction models have not been used as they should be, although routine procedures are able to give sea surface wind fields at the intervals of 6 hours. With the development of sp…  相似文献   
85.
用TRMM/TMI估算HUBEX试验区的云中液态水   总被引:4,自引:3,他引:4  
文中应用热带降雨测量卫星微波成像仪的微波遥感资料反演云中液态水。由于微波成像仪85.5 GHz通道对云中液态水非常敏感,通过离散纵坐标矢量辐射传输模式,运用迭代的方法可以有效地反演出陆地上空非降水云中的液态水路径。在淮河流域能量与水分循环试验中,分别运用微波成像仪85.5 GHz垂直极化单通道和微波成像仪85.5 GHz极化亮温差两种方法来估算陆地上空的云中液态水路径,反演结果与地基微波辐射计的测量结果是较为一致的。当地表比辐射率或地表温度误差较大时,用极化亮温差法估算云中液态水路径相对较好,尤其是对于低云,因为该方法对地表温度不敏感。  相似文献   
86.
数字地震数据的处理研究—真实地面运动的复原   总被引:2,自引:1,他引:2  
讨论了在频域中真实地面运动的复原问题,借助于一个稳定的六阶带通滤波器可使地震仪反演系统趋于稳定,最后由关分方程递归求出真实地动位移,结果表明,对同一个地震,不同的仪器其原始响应不同,但由其复原的真实地面运动结果却有相当好的一致性。这证明了所采用的复原方法的可用性。  相似文献   
87.
王向东  廖洞贤 《气象学报》1997,55(4):484-491
从原始方程出发,应用大气运动的对称反对称性理论,就赤道地区一呈偶极子分布的反对称冷热源对越赤道气流的形成和维持作用进行了定性分析。结果表明,非绝热加热的反对称分布对越赤道气流的影响是通过诱发和维持反对称的气压场分量来实现的。即在热源上空低层形成低压,高层形成高压;在热汇上空形成相反的气压场。这样,在赤道上空高、低层就将形成与相应气压梯度方向一致的越赤道气流  相似文献   
88.
An analysis of the Zihuatanejo, Mexico, earthquake of 1994 December 10 ( M = 6.6), based on teleseismic and near-source data, shows that it was a normal-faulting, intermediate-depth ( H = 50 ± 5 km) event. It was located about 30 km inland, within the subducted Cocos plate. The preferred fault plane has an azimuth of 130°, a dip of 79° and a rake of −86°. The rupture consisted of two subevents which were separated in time by about 2 s, with the second subevent occurring downdip of the first. The measured stress drop was relatively high, requiring a Δσ of about a kilobar to explain the high-frequency level of the near-source spectra. A rough estimate of the thickness of the seismogenic part of the oceanic lithosphere below Zihuatanejo, based on the depth and the rupture extent of this event, is 40 km.
This event and the Oaxaca earthquake of 1931 January 15 ( M = 7.8) are the two significant normal-faulting, intermediate-depth shocks whose epicentres are closest to the coast. Both of these earthquakes were preceded by several large to great shallow, low-angle thrust earthquakes, occurring updip. The observations in other subduction zones show just the opposite: normal-faulting events precede, not succeed, updip, thrust shocks. Indeed, the thrust events, soon after their occurrence, are expected to cause compression in the slab, thus inhibiting the occurrence of normal-faulting events. To explain the occurrence of the Zihuatanejo earthquake, we note that the Cocos plate, after an initial shallow-angle subduction, unbends and becomes subhorizontal. In the region of the unbending, the bottom of the slab is in horizontal extension. We speculate that the large updip seismic slip during shallow, low-angle thrust events increases the buckling of the slab, resulting in an incremental tensional stress at the bottom of the slab and causing normal-faulting earthquakes. This explanation may also hold for the 1931 Oaxaca event.  相似文献   
89.
Vertical seismic compressional- and shear-wave (P-and S-wave) profiles were collected from three shallow boreholes in sediment of the upper Mississippi embayment. The site of the 60-m hole at Shelby Forest, Tennessee, is on bluffs forming the eastern edge of the Mississippi alluvial plain. The bluffs are composed of Pleistocene loess, Pliocene-Pleistocene alluvial clay and sand deposits, and Tertiary deltaic-marine sediment. The 36-m hole at Marked Tree, Arkansas, and the 27-m hole at Risco, Missouri, are in Holocene Mississippi river floodplain sand, silt, and gravel deposits. At each site, impulsive P- and S-waves were generated by man-made sources at the surface while a three-component geophone was locked downhole at 0.91-m intervals.

Consistent with their very similar geology, the two floodplain locations have nearly identical S-wave velocity (VS) profiles. The lowest VS values are about 130 m s−1, and the highest values are about 300 m s−1 at these sites. The shear-wave velocity profile at Shelby Forest is very similar within the Pleistocene loess (12 m thick); in deeper, older material, VS exceeds 400 m s−1.

At Marked Tree, and at Risco, the compressional-wave velocity (VP) values above the water table are as low as about 230 m s−1, and rise to about 1.9 km s−1 below the water table. At Shelby Forest, VP values in the unsaturated loess are as low as 302 m s−1. VP values below the water table are about 1.8 km s−1. For the two floodplain sites, the VP/VS ratio increases rapidly across the water table depth. For the Shelby Forest site, the largest increase in the VP/VS ratio occurs at 20-m depth, the boundary between the Pliocene-Pleistocene clay and sand deposits and the Eocene shallow-marine clay and silt deposits.

Until recently, seismic velocity data for the embayment basin came from eartquake studies, crustal-scale seismic refraction and reflection profiles, sonic logs, and from analysis of dispersed earthquake surface waves. Since 1991, seismic data for shallow sediment obtained from reflection, refraction, crosshole and downhole techniques have been obtained for sites at the northern end of the embayment basin. The present borehole data, however, are measured from sites representative of large areas in the Mississippi embayment. Therefore, they fill a gap in information needed for modeling the response of the embayment to destructive seismic shaking.  相似文献   

90.
We present an overview of our recent results on utilizing small earthquakes in the earthquake engineering practice. Site-specific ground motion time-histories of large earthquakes can be successfully simulated using recordings of small earthquakes which are often referred to as 'empirical Green's functions' in seismology. Another important practical problem is whether and how these observations can be used in seismic risk studies which are based on empirical attenuation relations for ground motion parameters. We study a possibility of extrapolating attenuation relations for small earthquakes, to larger magnitudes using the data from the Garner Valley downhole array in Southern California. Finally we introduce efficient ground motion processing techniques in frequency- and time-domains and apply them to site response estimation.  相似文献   
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