2007～2010年云南GPS观测大气可降水量特征分析   总被引：2，自引：0，他引：2  

海云莎  孙绩华  陈新梅 《云南地理环境研究》2011,23(2):78-84

利用最新云南地基GPS站观测和探空观测资料分析表明:GPS/PWV和探空大气可降水量变化趋势一致,相关性好;云南省GPS/PWV年内干湿季气候特征分明,湿季开始前GPS/PWV月变率小于干季开始前的月变率;全省GPS/PWV年平均日变化峰值和谷值出现时间一致,勐腊、蒙自和昆明具有准双峰型特征;勐腊站干季、湿季日变化明显不同,其余测站干季和湿季的PWV日变化特征与全年平均日变化特征基本一致。GPS/PWV资料能够反应云南雨季开始期时空演变趋势。  相似文献   

布尔莎模型在GPS时间序列融合中的应用     

王紫燕  林树  武艳强  占伟  丁晓光 《中国地震》2013,29(1):68-74

利用“中国地壳运动观测网络”基准网与全球IGS站的公共站点,采用布尔莎模型求取坐标转换7参数,将地壳观测网络工程基准站点位时间序列与全球解进行绑定.结果显示,转换得到的时间序列N、E向中误差约为2、3mm,与直接融合得到的时间序列的单天误差水平相当,转换得到的站间大地线误差大部分在6mm内,表明该转换方法是可行的.  相似文献   

中国东南屯溪-温州宽角地震资料去广角效应成像     

张智  董超  李飞  王海燕 《地球物理学进展》2013,28(3)

由于长排列广角地震采集中必定存在超临界角的广角反射信息,广角反射信息相对临界角内反射信息存在随偏移距变化的时移现象.本文研究了去广角效应下的走时反演成像,并将其应用到东南屯溪—温州的宽角地震资料.通过拾取中国东南屯溪—温州剖面宽角实际地震资料中P波垂直分量拾取到的反射P波走时,继而使用遗传反演方法进行处理,得到了该区丰乐、新安江、松阳、青田以及洞头五炮去广角效应与未考虑广角效应情况下的一维速度深度曲线,并对比了去广角效应前后的地壳结构界面形态.结果表明,广角效应去除前后影响主要体现在壳内层速度差异,地壳浅层界面深度的广角效应明显强于深层界面.  相似文献   

Research on wind-induced responses of a large-scale membrane structure   总被引：1，自引：1，他引：0  

Zhou Xuanyi  Han Zhihui  Gu Ming  Zhang An-an  Zhang Weiyu  Fang Wei 《地震工程与工程振动(英文版)》2013,12(2):297-305

The wind-induced responses of a large-scale membrane structure, Expo Boulevard, are evaluated in this study. To obtain the wind pressure distribution on the roof surface, a wind tunnel test is performed. A brief analysis of wind pressure on the membrane roof is conducted first and then an analysis of the wind-induced responses of the structure is carried out using a numerical integral method in the time domain. In the process of calculation, the geometrical nonlinearity is taken into account. Results indicate that mean, RSM and peak values of the structure responses increase nonlinearly while the approaching flow velocity increases. Strong nonlinear characteristics are observed in the displacement responses, whereas the responses of nodal stress and cable axial force show minimal nonlinear properties when the membrane structure is subjected to wind loads. Different values of the damping ratio only have a minimal impact on the RSM response of the structure because the background component is a dominant part of the total dynamic response and the resonant component is too small. As the damping ratio increases from 0.02 to 0.05, the RMS responses of vertical displacement, nodal stress and cable axial force decrease by 8.1%, 6.7% and 17.9%, respectively. Since the mean component plays a significant role in the wind-induced response, the values of the gust response factor are not high for Expo Boulevard.  相似文献   

Dynamic interaction numerical models in the time domain based on the high performance scaled boundary finite element method     

Jianbo Li  Jun Liu  Gao Lin 《地震工程与工程振动(英文版)》2013,12(4):541-546

Consideration of structure-foundation-soil dynamic interaction is a basic requirement in the evaluation of the seismic safety of nuclear power facilities. An efficient and accurate dynamic interaction numerical model in the time domain has become an important topic of current research. In this study, the scaled boundary finite element method （SBFEM） is improved for use as an effective numerical approach with good application prospects. This method has several advantages, including dimensionality reduction, accuracy of the radial analytical solution, and unlike other boundary element methods, it does not require a fundamental solution. This study focuses on establishing a high performance scaled boundary finite element interaction analysis model in the time domain based on the acceleration unit-impulse response matrix, in which several new solution techniques, such as a dimensionless method to solve the interaction force, are applied to improve the numerical stability of the actual soil parameters and reduce the amount of calculation. Finally, the feasibility of the time domain methods are illustrated by the response of the nuclear power structure and the accuracy of the algorithms are dynamically verified by comparison with the refinement of a large-scale viscoelastic soil model.  相似文献   

Statistical moment-based structural damage detection method in time domain     

J.Zhang  Y.L.Xu  J.Li  Y.Xia  J.C.Li 《地震工程与工程振动(英文版)》2013,12(1):13-23

A novel structural damage detection method with a new damage index,i.e.,the statistical moment-based damage detection(SMBDD) method in the frequency domain,has been recently proposed.The aim of this study is to extend the SMBDD method in the frequency domain to the time domain for building structures subjected to non-Gaussian and non-stationary excitations.The applicability and effectiveness of the SMBDD method in the time domainis verified both numerically and experimentally.Shear buildings with various damage scenarios are first numerically investigated in the time domain taking into account the effect of measurement noise.The applicability of the proposed method in the time domain to building structures subjected to non-Gaussian and non-stationary excitations is then experimentally investigated through a series of shaking table tests,in which two three-story shear building models with four damage scenarios aretested.The identified damage locations and severities are then compared with the preset values.The comparative results are found to be satisfactory,and the SMBDD method is shown to be feasible and effective for building structures subjected to non-Gaussian and non-stationary excitations.  相似文献   

库车坳陷复杂高陡构造地震成像研究   总被引：2，自引：1，他引：1       下载免费PDF全文

符力耘  肖又军  孙伟家  吴超  管西竹  张敬洲 《地球物理学报》2013,56(6):1985-2001

复杂构造地震成像主要取决于叠前地震数据品质、偏移速度可靠性和偏移算子成像精度. 库车坳陷异常复杂的近地表条件导致极低信噪比的地震采集数据. 该区逆冲推覆高陡构造刺穿盐体大面积分布, 盐层厚度变化大、顶底面形态复杂, 盐下断裂带破碎、小断块发育, 形成异常复杂的地震成像问题. 本文重点研究三个关键环节:(1)精细的叠前地震预处理研究: 根据该区地震地质复杂性和地震资料特征, 采用一些新的方法技术和技术组合从振幅与时移的大、中、小尺度变化三个层次来解决资料信噪比问题, 重建深部反射信号; (2)三级偏移速度分析研究:利用库车坳陷盐刺穿逆冲推覆构造建模理论及变速成图配套技术解决叠前时间偏移速度场时深转换问题,利用井约束低频速度地震迭代反演技术解决连井层速度场与偏移速度场的融合问题,实现从DMO速度分析、叠前时间偏移速度分析到叠前深度偏移速度分析的有机衔接,建立拓扑结构相对保持的叠前深度偏移速度模型;(3)基于退化Fourier偏移算子的半解析波动方程叠前时间和深度偏移研究, 极大地改善了地震偏移过程中高波数波的成像问题. 通过对库车坳陷大北、博孜、却勒、西秋4和西秋10等复杂高陡构造的叠前时间和深度偏移地震成像处理,取得了较好的应用效果.  相似文献   

Validation of ground‐motion simulations for historical events using MDoF systems     

Carmine Galasso  Peng Zhong  Farzin Zareian  Iunio Iervolino  Robert W. Graves 《地震工程与结构动力学》2013,42(9):1395-1412

The study presented in this paper addresses the issue of engineering validation of Graves and Pitarka's (2010) hybrid broadband ground motion simulation methodology with respect to some well‐recorded historical events and considering the response of multiple degrees of freedom (MDoF) systems. Herein, validation encompasses detailed assessment of how similar is, for a given event, the seismic response due to comparable hybrid broadband simulated records and real records. In the first part of this study, in order to investigate the dynamic response of a wide range of buildings, MDoF structures are modeled as elastic continuum systems consisting of a combination of a flexural cantilever beam coupled with a shear cantilever beam. A number of such continuum systems are selected including the following: (1) 16 oscillation periods between 0.1 and 6 s; (2) three shear to flexural deformation ratios to represent respectively shear‐wall structures, dual systems, and moment‐resisting frames; and (3) two stiffness distributions along the height of the systems, that is, uniform and linear. Demand spectra in terms of generalized maximum interstory drift ratio (IDR) and peak floor acceleration (PFA) are derived using simulations and actual recordings for four historical earthquakes, namely, the 1979 M_w 6.5 Imperial Valley earthquake, 1989 M_w 6.8 Loma Prieta earthquake, 1992 M_w 7.2 Landers earthquake, and 1994 M_w 6.7 Northridge earthquake. In the second part, for two nonlinear case study structures, the IDR and PFA distributions over the height and their statistics, are obtained and compared for both recorded and simulated time histories. These structures are steel moment frames designed for high seismic hazard, 20‐story high‐rise and 6‐story low‐rise buildings. The results from this study highlight the similarities and differences between simulated and real records in terms of median and intra‐event standard deviation of logs of seismic demands for MDoF building systems. This general agreement, in a broad range of moderate and long periods, may provide confidence in the use of the simulation methodology for engineering applications, whereas the discrepancies, statistically significant only at short periods, may help in addressing improvements in generation of synthetic records. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Reducing the non-axisymmetry of a planetary dynamo and an application to saturn     

D. J. Stevenson 《地球物理与天体物理流体动力学》2013,107(1-2):113-127

Abstract

If a conducting fluid shell is undergoing spin-axisymmetric differential rotation and overlies the dynamo generating region of a planet then it is capable of greatly reducing the non-spin-axisymmetric components of the generated field, provided the appropriate magnetic Reynolds number is large. The model, closely related to the electromagnetic skin effect, is quantified and applied to Saturn. The observed small dipole tilt (～ 1°) of Saturn's magnetic field can be explained because of the presence of a stably stratified conducting layer overlying the dynamo region. This layer is a predicted consequence of the thermal evolution, arises because of the limited solubility of helium in metallic hydrogen (Stevenson, 1980), and appears to be required by the Voyager infrared observations indicating depletion of helium from Saturn's atmosphere. The much larger dipole tilt angles of Jupiter and the Earth indicate the absence of any such stable, differentially rotating layer with a large magnetic Reynolds number.  相似文献   

Generalized autoregressive conditional heteroscedasticity modelling of hydrologic time series   总被引：1，自引：0，他引：1  

R. Modarres  T. B. M. J. Ouarda 《水文研究》2013,27(22):3174-3191

The existence of time‐dependent variance or conditional variance, commonly called heteroscedasticity, in hydrologic time series has not been thoroughly investigated. This paper deals with modelling the heteroscedasticity in the residuals of the seasonal autoregressive integrated moving average (SARIMA) model using a generalized autoregressive conditional heteroscedasticity (GARCH) model. The model is applied to two monthly rainfall time series from humid and arid regions. The effect of Box–Cox transformation and seasonal differencing on the remaining seasonal heteroscedasticity in the residuals of the SARIMA model is also investigated. It is shown that the seasonal heteroscedasticity in the residuals of the SARIMA model can be removed using Box–Cox transformation along with seasonal differencing for the humid region rainfall. On the other hand, transformation and seasonal differencing could not remove heteroscedasticity from the residuals of the SARIMA model fitted to rainfall data in the arid region. Therefore, the GARCH modelling approach is necessary to capture the heteroscedasticity remaining in the residuals of a SARIMA model. However, the evaluation criteria do not necessarily show that the GARCH model improves the performance of the SARIMA model. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献