布谷鸟马尔科夫链蒙特卡洛混合高斯地质统计学随机反演

地质统计学随机反演可以获得比常规反演更高分辨率的结果,目前已成为储层高分辨率预测的主流方法.地下不同岩相储层参数存在明显差异,本文在地质统计学反演框架下构建了岩相和储层参数同步反演目标函数,实现不同岩相条件下储层参数分布精细描述.在求解该高维数据多参数同步反演问题时,本文将可以动态调节搜索步长的布谷鸟算法与马尔科夫链蒙...     

基于Born散射理论的二维黏声介质高斯波束正演

Born散射理论可以通过省略高阶项实现针对一次散射波场的模拟.在这一理论的基础上,本文提出了一种针对二维黏声介质的一次散射波场高斯束Born正演方法.在该方法中,格林函数通过一系列不同初射方向的高斯波束累加获得,可以计算多至走时波场,保证了正演算法的计算精度.同时为了提高计算效率,正演方法使用了wavelet-bank方式合成局部平面波.区别于针对声波介质正演的wavelet-bank使用方法,文中将介质黏滞性信息融入了局部平面波的wavelet-bank合成方法中,以此实现针对黏声介质的快速一次散射波场模拟.两个模型的计算结果表明：本文提出的黏声介质高斯波束正演方法具有良好的计算精度以及较高的计算效率.

     

Estimation of base motion in instrumented steel buildings using output‐only system identification

A procedure to estimate the seismic motion at the base of a building from measured acceleration response at two or more floors is presented. The proposed method is comprised of two steps. In the first step, the dynamic characteristics of the building are inferred by using an output‐only system identification procedure. In the second step, the motion of the base of the building is estimated by using the transfer function of a simplified building model consisting of a shear and flexural continuous beam together with dynamic properties obtained in the first step. The proposed method is validated first with an analytical model subjected to the 1940 El Centro ground motion and then with an instrumented building in California that experienced the 1994 Northridge earthquake, and the ground motions at the base of the building are available. It is shown that the proposed method is capable of providing very good estimates of the motion at the base. The use of the proposed method is finally illustrated on an instrumented building, where the sensor at the base of the building did not function during the 1994 Northridge earthquake. Copyright © 2013 John Wiley & Sons, Ltd.     

Gabor‐frame‐based Gaussian packet migration

We present a Gaussian packet migration method based on Gabor frame decomposition and asymptotic propagation of Gaussian packets. A Gaussian packet has both Gaussian‐shaped time–frequency localization and space–direction localization. Its evolution can be obtained by ray tracing and dynamic ray tracing. In this paper, we first briefly review the concept of Gaussian packets. After discussing how initial parameters affect the shape of a Gaussian packet, we then propose two Gabor‐frame‐based Gaussian packet decomposition methods that can sparsely and accurately represent seismic data. One method is the dreamlet–Gaussian packet method. Dreamlets are physical wavelets defined on an observation plane and can represent seismic data efficiently in the local time–frequency space–wavenumber domain. After decomposition, dreamlet coefficients can be easily converted to the corresponding Gaussian packet coefficients. The other method is the Gabor‐frame Gaussian beam method. In this method, a local slant stack, which is widely used in Gaussian beam migration, is combined with the Gabor frame decomposition to obtain uniform sampled horizontal slowness for each local frequency. Based on these decomposition methods, we derive a poststack depth migration method through the summation of the backpropagated Gaussian packets and the application of the imaging condition. To demonstrate the Gaussian packet evolution and migration/imaging in complex models, we show several numerical examples. We first use the evolution of a single Gaussian packet in media with different complexities to show the accuracy of Gaussian packet propagation. Then we test the point source responses in smoothed varying velocity models to show the accuracy of Gaussian packet summation. Finally, using poststack synthetic data sets of a four‐layer model and the two‐dimensional SEG/EAGE model, we demonstrate the validity and accuracy of the migration method. Compared with the more accurate but more time‐consuming one‐way wave‐equation‐based migration, such as beamlet migration, the Gaussian packet method proposed in this paper can correctly image the major structures of the complex model, especially in subsalt areas, with much higher efficiency. This shows the application potential of Gaussian packet migration in complicated areas.     

Copula‐based uncertainty modelling: application to multisensor precipitation estimates

The multisensor precipitation estimates (MPE) data, available in hourly temporal and 4 km × 4 km spatial resolution, are produced by the National Weather Service and mosaicked as a national product known as Stage IV. The MPE products have a significant advantage over rain gauge measurements due to their ability to capture spatial variability of rainfall. However, the advantages are limited by complications related to the indirect nature of remotely sensed precipitation estimates. Previous studies confirm that efforts are required to determine the accuracy of MPE and their associated uncertainties for future use in hydrological and climate studies. So far, various approaches and extensive research have been undertaken to develop an uncertainty model. In this paper, an ensemble generator is presented for MPE products that can be used to evaluate the uncertainty of rainfall estimates. Two different elliptical copula families, namely, Gaussian and t‐copula are used for simulations. The results indicate that using t‐copula may have significant advantages over the well‐known Gaussian copula particularly with respect to extremes. Overall, the model in which t‐copula was used for simulation successfully generated rainfall ensembles with similar characteristics to those of the ground reference measurements. Copyright © 2010 John Wiley & Sons, Ltd.     

VTI介质角度域转换波高斯束偏移成像方法研究

转换波偏移可以利用纵横波波场信息,得到高分辨率的成像结果,从而为油藏描述提供高质量的地震资料.目前的研究主要是利用纵波波场信息进行偏移成像,然而,传统的纵波方法在复杂探区成像时具有一定的局限性.为此,本文在各向异性介质声波射线追踪算法的基础上,推导出各向异性介质转换波射线追踪方程,发展了一种转换波射线追踪算法;并将研究的追踪算法应用到偏移成像中,提出了一种各向异性VTI介质角度域转换波高斯束偏移成像方法.通过各向异性VTI介质断块模型和复杂构造模型试算,说明了本文方法的正确性和有效性.模型试算的结果表明,在考虑地下各向异性时,本文研究的方法具有更好的成像效果,提取的角道集结果可以为偏移速度分析提供依据.

     

黏弹介质VSP高斯射线正演模拟

为了研究黏弹介质中VSP地震勘探地震波的波场特征,在理论分析地震波在黏弹介质中传播特性的基础上,采用高斯射线束方法对黏弹介质VSP地震进行波场正演模拟.正演结果与各向同性介质及VTI介质VSP正演对比,体现了地震波在黏弹介质中传播的特点.同时VSP高斯束正演方法能够解决复杂构造正演盲区问题,其动力学特征更能反映黏弹介质对地震波传播的影响,计算速度又优于波动方程类正演方法,正演结果能有效分辨地震波场特征,为VSP数据处理与解释提供了借鉴.     

方钢管混凝土柱-不等高钢梁框架节点抗剪承载力分析

为研究方钢管混凝土柱-H型不等高钢梁框架节点的抗剪承载力,分析其破坏机理,建立适用于不等高钢梁节点的抗剪计算模型,提出了节点的抗剪承载力计算公式,比较了基于不同抗剪模型建立的抗剪承载力计算值与试验值的差异性。结果表明:节点域的破坏模式主要为上核心区的剪切斜压破坏;节点域抗剪承载力主要由钢管腹板、核心区混凝土主斜压杆及约束斜压杆共同承担。对比分析表明:提出的节点屈服抗剪承载力和极限抗剪承载力理论公式计算值更为接近试验值,验证了方钢管混凝土柱-不等高钢梁框架节点传力机理和承载力计算公式的正确性。     

巢湖藻类高斯垂向分布结构参数的遥感估算

藻类垂向分布异质性导致了遥感反演的湖泊表层叶绿素a浓度结果与单元水柱内藻类生物量间不存在一一对应的关系,因此有效确定藻类垂向分布结构是遥感反演湖泊藻类生物量的基础.受自身因素和外环境条件的影响,藻类垂向分布结构呈现出多种类型,其中高斯类型应用最广.本文基于3200组HydroLight模拟的高斯垂向数据构建BP神经网络,实现用MODIS数据相对应的3个波段的遥感反射比R_(rs)(469)、R_(rs)(555)、R_(rs)(645)和表层叶绿素a浓度共同估算高斯垂向分布结构参数h和σ.经巢湖地面实测数据验证显示,h和σ的估算值与实测值的相关系数分别为0.97和0.95,对应的相对误差分别为13.20%和12.36%,两者相对误差同时小于30%的占总数据量的87.5%,表明该BP神经网络估算巢湖藻类高斯垂向分布结构的有效性和准确性,为基于卫星遥感数据获取湖泊藻类生物量提供了重要的理论基础.     

基于光流校正的复杂地形区多时相遥感影像配准

几何配准是影像后续处理的重要前提,是遥感信息处理领域研究的热点之一.复杂地形区多时相遥感影像的高精度配准一直是难以突破的难题,光流估计法通过逐像素位移增量解算为此提供了可行的解决思路,但光流法对地物变化异常敏感,经常导致计算的光流场及配准影像存在异常.为此,本文提出一种基于光流校正的复杂地形区多时相遥感影像配准方法,采...