复波场的实部和虚部对同时源波形反演的影响

高精度的成像需要准确的速度场信息,波形反演被认为是目前具有最高分辨率的速度反演方法之一.计算效率是目前全波形反演需要考虑的一个主要问题.为了很好地解决计算效率的问题,本文引入了一种高效的无串扰同时源反演方法,并详细介绍了其原理与计算流程.同时,基于此多震源同时反演方法,本文拓展出实波场反演、虚波场反演及复波场反演的三种反演策略,进而分析复波场的实部和虚部对全波形反演的影响.实验表明,相比于复波场全波形反演,无论是实波场反演还是虚波场反演,反演分辨率有所降低;相比于实波场反演,虚波场反演对初始模型的依赖性较小,目标函数的非线性较弱;最后,通过使用组合反演策略,即初始阶段采用虚波场反演,中后期阶段采用复波场反演,不仅可以降低反演的非线性,而且能够保证高精度建模.

     

Identification of modal parameters of non‐classically damped linear structures under multi‐component earthquake loading

A method for parametric system identification of classically damped linear system in frequency domain is adopted and extended for non‐classically damped linear systems subjected up to six components of earthquake ground motions. This method is able to work in multi‐input/multi‐output (MIMO) case. The response of a two‐degree‐of‐freedom model with non‐classical damping, excited by one‐component earthquake ground motion, is simulated and used to verify the proposed system identification method in the single‐input/multi‐output case. Also, the records of a 10 storey real building during the Northridge earthquake is used to verify the proposed system identification method in the MIMO case. In this case, at first, a single‐input/multi‐output assumption is considered for the system and modal parameters are identified, then other components of earthquake ground motions are added, respectively, and the modal parameters are identified again. This procedure is repeated until all four components of earthquake ground motions which are measured at the base level of the building are included in the identification process. The results of identification of real building show that consideration of non‐classical damping and inclusion of the multi‐components effect of earthquake ground motions can improve the least‐squares match between the finite Fourier transforms of recorded and calculated acceleration responses. Copyright © 2006 John Wiley & Sons, Ltd.     

Non‐linear system identification of the versatile‐typed structures by a novel signal processing technique

Non‐linear structural identification problems have raised considerable research efforts since decades, in which the Bouc–Wen model is generally utilized to simulate non‐linear structural constitutive characteristic. Support vector regression (SVR), a promising data processing method, is studied for versatile‐typed structural identification. First, a model selection strategy is utilized to determine the unknown power parameter of the Bouc–Wen model. Meanwhile, optimum SVR parameters are selected automatically, instead of tuning manually. Consequently, the non‐linear structural equation is rewritten in linear form, and is solved by the SVR technique. A five‐floor versatile‐type structure is studied to show the effectiveness of the proposed method, in which both power parameter known and unknown cases are investigated. Copyright © 2007 John Wiley & Sons, Ltd.     

基于频率摄动理论识别悬臂梁损伤方法的试验研究

将悬臂梁的振动理论和矩阵摄动理论相结合,推出悬臂梁损伤或缺陷的识别公式.通过2根钢悬臂梁的试验,测出其损伤前后的频率,并根据测试结果对梁的损伤程度进行判定.结果表明,用摄动理论不仅可以识别悬臂构件的损伤位置,还可以定量求出其损伤程度.     

震后预报的某些研究

通过研究华北北部中强以上地震震后地震活动，地形变、地电阻率、水化学和水位变化特征，给出了各单项方法识别震后效应与新地震异常的标志。为了综合判别震后短临异常变化是震后效应或新异常，研制了一套综合识别计算机程序系统，该系统考虑了已发生的强震序列类型，地震活动背景特征以及强震前后前兆短临异常变化形态，充分利用专家的知识与经验进行推理和判断。通过运行典型事例表明该系统功能较强，使用方便。系统的实现是专家系     

一种有效的结构动态参数识别方法

本文以优化算法中单纯形法为基础,提出了一种只有利用实测的结构模态部分信息识别其结构参数的方法。数值计算表明,该算法具有良好的精度和适用性。     

Inversion of focal mechanism and events identification using an improved relative amplitude method

The relative amplitude method(RAM) is more suitable for source inversion of low magnitude earthquakes because it avoids the modeling of short-period waveforms.We introduced an improved relative amplitude method(IRAM) which is more robust in practical cases.The IRAM uses a certain function to quantify the fitness between the observed and the predicted relative amplitudes among direct P wave,surface reflected pP and sP waves for a given focal mechanism.Using the IRAM,we got the fault-plane solutions of two ea...     

System identification of the Vincent Thomas suspension bridge using earthquake records

The Vincent Thomas Bridge in the Los Angeles metropolitan area, is a critical artery for commercial traffic flow in and out of the Los Angeles Harbor, and is at risk in the seismically active Southern California region, particularly because it straddles the Palos Verdes fault zone. A combination of linear and non‐linear system identification techniques is employed to obtain a complete reduced‐order, multi‐input–multi‐output (MIMO) dynamic model of the Vincent Thomas Bridge based on the dynamic response of the structure to the 1987 Whittier and 1994 Northridge earthquakes. Starting with the available acceleration measurements (which consists of 15 accelerometers on the bridge structure and 10 accelerometers at various locations on its base), an efficient least‐squares‐based time‐domain identification procedure is applied to the data set to develop a reduced‐order, equivalent linear, multi‐degree‐of‐freedom model. Although not the main focus of this study, the linear system identification method is also combined with a non‐parametric identification technique, to generate a reduced‐order non‐linear mathematical model suitable for use in subsequent studies to predict, with good fidelity, the total response of the bridge under arbitrary dynamic environments. Results of this study yield measurements of the equivalent linear modal properties (frequencies, mode shapes and non‐proportional damping) as well as quantitative measures of the extent and nature of non‐linear interaction forces arising from strong ground shaking. It is shown that, for the particular subset of observations used in the identification procedure, the apparent non‐linearities in the system restoring forces are quite significant, and they contribute substantially to the improved fidelity of the model. Also shown is the potential of the identification technique under discussion to detect slight changes in the structure's influence coefficients, which may be indicators of damage and degradation in the structure being monitored. Difficulties associated with accurately estimating damping for lightly damped long‐span structures from their earthquake response are discussed. The technical issues raised in this paper indicate the need for added spatial resolution in sensor instrumentation to obtain identified mathematical models of structural systems with the broadest range of validity. Copyright © 2003 John Wiley & Sons, Ltd.     

测井曲线概率分布法识别四川盆地火山岩气水层

火山岩的矿物成分复杂,主要矿物有石英、正长石、斜长石、云母、角闪石、辉石和橄榄石.不同岩性的储层物性和孔隙结构类型各不相同,这给火山岩气水层判别造成很大困难.基于测井资料,首先采用中子-密度交会图的方法求取孔隙度,然后结合实验室的岩电参数以及测井的电阻率曲线,构建P1/2概率分布曲线,根据概率曲线的分布形态来识别火山岩...