Shear Wave Inversion Considering The Crescendo Of Regional Characteristics

The shear wave velocity is an important parameter to calculate field dynamic response and determine seismic site category of buildings.It is one of the important earthquake engineering research subjects that how to accurately and quickly measure shear wave velocity.Recent years,based on fundamental mode dispersion curve obtained by small-scale micro-tremor observation array records,we can get s-wave velocity structure through inversion methods.The way that we mentioned above is differ from drilling exploration method and is gradually being accepted by engineers since its economy and convenience.But this kind of inversion problem has multiplicity solutions,the dispersion cures got from different s-wave velocity structures can be similar.It is a difficulty of promoting this method in engineering application area that how to effectively avoid the problem above and how to ensure the reliability of inversion results.Based on the problem that s-wave velocity of crescendo soil can be obtained by micro-tremor observation array records,this paper establishes a s-wave velocity retrieval method that is the most similar to the actual soil structure for the sense of probability,through introducing the general characteristics of s-wave velocity structure got by statistical methods in the process of inversion,on the basis of the MSCAMH method that can establish dispersion curve inverse problems.The result shows that,this method has a good precision and can easily avoid dispersion curve multiplicity solutions problem.This method can also increase the reliability of inversion results.Specific researches are as follows:1.This paper analyzes the basic feature of crescendo s-wave velocity structure in Heilongjiang Province,through extracting the drilling data of seismic risk assessment report in this region.On this basis,discusses the basic feature of fundamental mode Rayleigh wave dispersion curve in typical soil layer: Rayleigh wave dispersion curve is more sensitively about surface and deep soil parameters than middle tier.At last,figures out the f-? curve of the typical soil layer.2.Based on theoretical calculation,this paper does a deep analysis in the property of MSCAMH algorithm.Then analyzes in detail how the setup of initial model,the selection of objective function,the variance of proposal distribution and the function of proposal distribution can affect the precision and astringency of MSCAMH.It turns out that,a reasonable initial model can improve the precision and the speed of convergence effectively when using MSCAMH.Therefore,it is necessary to introduce regional characteristics of s-wave velocity structure,during the process of applying MSCAMH to solve Rayleigh wave dispersion curve inversion problems.This paper also suggests a new kind of objective function,for the problem that the Rayleigh wave dispersion curve obtained by micro-tremor observation array records exists distortion in low and high frequency,then increases the weight of residual between middle and low frequency band target dispersion curve and simulated dispersion curve,in the new objective function.It builds a s-wave velocity inversion method which can make the result relatively stable.3.We select a field which contains drilling data,lay out a number of micro-tremor observation arrays,attain fundamental mode Rayleigh wave dispersion curve based on the ESPAC method suitable for flexible array deployment.Then we acquire the increasing type s-wave velocity structure in the area using the inversion method established in this paper.Contrastively analyze inversion result and the drilling data,the result shows that,the s-wave velocity structure calculated by MSCAMH is similar to the average shear wave velocity structure in this area.Verify reliability of the method established in this paper about how to acquire s-wave velocity structure of increasing type soil layer using micro-tremor observation array.