非均匀套管井中的过套管电阻率测井响应   总被引：13，自引：2，他引：11       下载免费PDF全文

高杰  刘福平  包德洲  程希  杨长春 《地球物理学报》2008,51(4):1255-1261

套管井壁的电势分布包含了金属套管和地层模型的信息,套管电阻率的变化对过套管电阻率测井有重要影响,本文考虑了套管电阻率的变化对传输线方程系数的影响,给出了非均匀套管壁电势分布的计算方法．利用套管井壁电势分布实现了非均匀套管测井响应的计算,考察了套管电阻率变化对过套管电阻率测井响应的影响,模拟结果表明,套管的变薄或变厚对测井响应均有一定影响,当套管电阻突然变小（套管变厚）或突然变大（套管变薄）时过套管电阻率测井异常发生在套管电阻突变界面附近．模拟结果还显示电极距对测井结果有明显影响．  相似文献   

Ground-motion Attenuation Relation from Strong-motion Records of the 2001 Mw 7.7 Bhuj Earthquake Sequence (2001–2006), Gujarat, India     

Prantik Mandal  N. Kumar  C. Satyamurthy  I. P. Raju 《Pure and Applied Geophysics》2009,166(3):451-469

Predictive relations are developed for peak ground acceleration (PGA) from the engineering seismoscope (SRR) records of the 2001 M_w 7.7 Bhuj earthquake and 239 strong-motion records of 32 significant aftershocks of 3.1 ≤ M_w ≤ 5.6 at epicentral distances of 1 ≤ R ≤ 288 km. We have taken advantage of the recent increase in strong-motion data at close distances to derive new attenuation relation for peak horizontal acceleration in the Kachchh seismic zone, Gujarat. This new analysis uses the Joyner-Boore’s method for a magnitude-independent shape, based on geometrical spreading and anelastic attenuation, for the attenuation curve. The resulting attenuation equation is, where, Y is peak horizontal acceleration in g, M_w is moment magnitude, r_jb is the closest distance to the surface projection of the fault rupture in kilometers, and S is a variable taking the values of 0 and 1 according to the local site geology. S is 0 for a rock site, and, S is 1 for a soil site. The relation differs from previous work in the improved reliability of input parameters and large numbers of strong-motion PGA data recorded at short distances (0–50 km) from the source. The relation is in demonstrable agreement with the recorded strong-ground motion data from earthquakes of M_w 3.5, 4.1, 4.5, 5.6, and 7.7. There are insufficient data from the Kachchh region to adequately judge the relation for the magnitude range 5.7 ≤ M_w ≤ 7.7. But, our ground-motion prediction model shows a reasonable correlation with the PGA data of the 29 March, 1999 Chamoli main shock (M_w 6.5), validating our ground-motion attenuation model for an M_w6.5 event. However, our ground-motion prediction shows no correlation with the PGA data of the 10 December, 1967 Koyna main shock (M_w 6.3). Our ground-motion predictions show more scatter in estimated residual for the distance range (0–30 km), which could be due to the amplification/noise at near stations situated in the Kachchh sedimentary basin. We also noticed smaller residuals for the distance range (30–300 km), which could be due to less amplification/noise at sites distant from the Kachchh basin. However, the observed less residuals for the longer distance range (100–300 km) are less reliable due to the lack of available PGA values in the same distance range.  相似文献   

横向各向同性介质弹性波多分量叠前逆时偏移   总被引：17，自引：5，他引：12       下载免费PDF全文

杜启振  秦童 《地球物理学报》2009,52(3):801-807

随着油气勘探程度的提高,隐蔽油气藏在增储上产方面起到了重要作用,因此发展基于各向异性介质的多分量偏移方法是非常必要的.本文基于横向各向同性（VTI）介质,从二维弹性波速度\|应力方程出发,通过在时间上的二阶差分和空间上的交错网格高阶差分对方程进行离散,得到弹性波交错网格高阶差分的多分量逆时偏移算子.在激发时间成像条件的应用过程中引入Poynting矢量进行成像并消除逆时偏移所引起的低频干扰,在此基础上实现了VTI介质中二维弹性波叠前多分量逆时深度偏移.理论模型的偏移处理表明,该方法能够对地层进行准确成像,并可以消除逆时偏移所引起的低频噪声.  相似文献   

用积分方程法模拟各向异性地层中三维电性异常体的电磁响应   总被引：11，自引：5，他引：6       下载免费PDF全文

陈桂波  汪宏年  姚敬金  杨守文 《地球物理学报》2009,52(8):2174-2181

本文研究并建立了一种模拟各向异性地层中三维电性异常体电磁响应的积分方程算法.首先讨论了并矢Green函数及其相关积分的计算,将水平层状各向异性地层中的电场并矢Green函数分解成含有奇异项的直达波与非奇异的来自各个层界面的反射和透射波两个部分,再应用等效体积单元和表面积分技术对积分方程的奇异核进行离散化处理以便提高离散方程的精度.然后为了节省计算机内存以及计算时间,引入基于Krylov子空间的迭代算法求解积分方程的离散化矩阵方程.最后通过与现有文献中的结果作对比从而检验了所述算法的有效性,并结合具体算例考察分析了地层的各向异性对三维电性异常体电磁响应的影响特征和规律.  相似文献   

A cluster-optimizing regression-based approach for precipitation spatial downscaling in mountainous terrain     

Huade Guan  John L. Wilson  Hongjie Xie 《Journal of Hydrology》2009,375(3-4):578-588

Precipitation temporal and spatial variability often controls terrestrial hydrological processes and states. Common remote-sensing and modeling precipitation products have a spatial resolution that is often too coarse to reveal hydrologically important spatial variability. A statistical algorithm was developed for downscaling low-resolution spatial precipitation fields. This algorithm auto-searches precipitation spatial structures (rain-pixel clusters), and orographic effects on precipitation distribution without prior knowledge of atmospheric setting. It is composed of three components: rain-pixel clustering, multivariate regression, and random cascade. The only required input data for the downscaling algorithm are coarse-pixel precipitation map and a topographic map. The algorithm was demonstrated with 4 km × 4 km Next Generation Radar (NEXRAD) precipitation fields, and tested by downscaling NEXRAD-aggregated 16 km × 16 km precipitation fields to 4 km × 4 km pixel precipitation, which was then compared to the original NEXRAD data. The demonstration and testing were performed at both daily and hourly temporal resolutions for the northern New Mexico mountainous terrain and the central Texas Hill Country. The algorithm downscaled daily precipitation fields are in good agreement with the original 4 km × 4 km NEXRAD precipitation, as measured by precipitation spatial structures and the statistics between the downscaling and the original NEXRAD precipitation maps. For three daily precipitation events, downscaled precipitation map reproduces precipitation variance of the disaggregation field, and with Pearson correlation coefficients between the downscaled map and the NEXRAD map of 0.65, 0.71, and 0.80. The algorithm does not perform as well on downscaling hourly precipitation fields at the examined scale range (from 16 km to 4 km), which underestimates precipitation variance of the disaggregation field. For a scale range from 4 km to 1 km, the algorithm has potential to perform well at both daily and hourly precipitation fields, indicated from good regression performance.  相似文献   

Equation on spatial variation of shallow water waves amplitude     

Yang Lian-gui  Hou Yi-jun 《中国海洋湖沼学报》1998,16(3):221-224

Boussinesq’s theory was used in this study on water waves entering shallow water showing that the spacial variation of the wave amplitude is nonlinear, and is governed by the Duffing equation usually applied to describe nonlinear oscillation in nature. Contribution No. 3324 from the Institute of Oceanology, Chinese Academy of Sciences. Project 49471276 supported by NSFC and the Ninth-Five-Year Key Project (KI952-s1-420) of the Chinese Academy of Sciences.  相似文献   

Rainfall and Obtaining Information Regarding Earthquake Development Processes from Groundwater Level     

Li Yong  Fang Wei  Ma Li 《中国地震研究》2008,22(1):52-61

Many factors can cause changes of groundwater level, such as the development process of an earthquake, rainfall, solid earth tides etc. Among these we are interested in information regarding earthquake development processes. Eliminating the influence of various disturbance factors is an effective way to obtain seismic development process information contained in the groundwater level. This paper provides two different ways to remove the rainfall effect, and compares the two methods by means of correlation analysis. Furthermore, based on these a logistic regression model is established to describe the seismicity level.  相似文献   

考虑动水压力影响的单柱式桥墩地震反应分析   总被引：3，自引：1，他引：2  

李富荣  陈国兴  王志华 《地震工程与工程振动》2008,28(2):114-121

在Morison方程的基础上,用附加水质量法考虑动水压力对桥墩的影响,以单柱式桥墩为研究对象,以ABAQUS有限元软件为计算平台,建立了考虑桩-土动力相互作用的单柱式桥墩地震反应分析模型,考虑土体和桥墩混凝土的动力非线性特征,分析了地震动作用下动水压力对单柱式桥墩的墩顶相对墩底位移、加速度、剪力和弯矩反应的影响,并探讨了水位对单柱式桥墩地震反应特性的影响。结果表明:动水压力改变桥墩的地震反应特性,增大了桥墩顶部相对底部的位移、墩顶绝对加速度和墩底的内力,水位变化影响桥墩的地震反应特性。对于深水桥墩抗震设计计算,考虑动水压力效应、水位变化是有必要的。  相似文献   

Modeling the potential distribution of shallow-seated landslides using the weights of evidence method and a logistic regression model： a case study of the Sabae Area, Japan   总被引：5，自引：0，他引：5  

Ru-Hua SONG  Daimaru HIROMU  Abe KAZUTOKI  Kurokawa USIO  Matsuura SUMIO 《国际泥沙研究》2008,23(2):106-118

A number of statistical methods are typically used to effectively predict potential landslide distributions. In this study two multivariate statistical analysis methods were used （weights of evidence and logistic regression） to predict the potential distribution of shallow-seated landslides in the Kamikawachi area of Sabae City, Fukui Prefecture, Japan. First, the dependent variable （shallow-seated landslides） was divided into presence and absence, and the independent variables （environmental factors such as slope and altitude） were categorized according to their characteristics. Then, using the weights of evidence （WE） method, the weights of pairs comprising presence （w^＋（i）） or absence （w^-（i））, and the contrast values for each category of independent variable （evidence）, were calculated, Using the method that integrated the weights of evidence method and a logistic regression model, score values were calculated for each category of independent variable. Based on these contrast values, three models were selected to sum the score values of every gird in the study area. According to a receiver operating characteristic curve analysis （ROC）, model 2 yielded the best fit for predicting the potential distribution of shallow-seated landslide hazards, with 89% correctness and a 54.5% hit ratio when the occurrence probability （OP） of landslides was 70%. The model was tested using data from an area close to the study region, and showed 94% correctness and a hit ratio of 45.7% when the OP of landslides was 70%. Finally, the potential distribution of shallow-seated landslides, based on the OP, was mapped using a geographical information system.  相似文献   

计算断层自发破裂过程的离散网格划分研究          下载免费PDF全文

刘启明  陈晓非 《地震学报》2008,30(5):449-455

离散化网格的空间步长选取在各种数值算法中都是一个很受关注的问题,在全空间均匀介质模型和简单离散化方案下,利用边界积分方程方法研究在自发破裂求解过程中动力学参数组合Dc和Te (Dc为临界滑动弱化位移,Te为有效的断层破裂面上的初始应力)对计算网格划分的影响,初步得到了Dc和Te参数空间中的有效计算网格的选取规律,对合理、有效地运用边界积分方程方法计算地震震源的破裂过程具有重要的指导意义.   相似文献