A method of obtaining a velocity-depth envelope from wide-angle seismic data

Summary. Due to the non-uniqueness of traveltime inversion of seismic data, it is more appropriate to determine a velocity-depth ( v-z ) envelope, rather than just a v-z function. Several methods of obtaining a v-z envelope by extremal inversion have been proposed, all of which invert the data primarily from either x-p , or T-p , or both domains. These extremal inversion methods may be divided into two groups: linear extremal and non-linear extremal. There is some debate whether the linearized perturbation techniques should be applied to the inherently non-linear problem of traveltime inversion. We have obtained a v-z envelope by extremal inversion in T-p with the constraint that the inversion paths also satisfy x-p observations. Thus we use data jointly in r-p and x-p , and yet avoid the linearity assumptions.
This joint, non-linear extremal inversion method has been applied to obtain a v-z envelope down to a depth of about 30 km in the Baltimore Canyon trough using x-t data from an Expanding Spread Profile acquired during the LASE project. We have found that the area enclosed by the v-z envelope is reduced by about 15 per cent using x-p control on the T-p inversion paths, compared to the inversion without x-p control.     

HVF������GPS��·��ЧӦ�о��е�Ӧ��

????????Helmert????????????Vondrak????????????HVF??????????????GPS??·??Ч????о????????????????????????????÷???????????Vondrak?????????????????????????????????Ч????????????????е????????????????÷????????·????????????GPS??·??Ч?????????????????????Ч????????·??Ч??????????????????GPS??λ?????     

基于改进的双线性旅行时插值的三维射线追踪

旅行时射线追踪的精度和效率一直是影响地震层析成像质量和效果的关键因素。这里在三维近地表速度结构层析成像应用中,结合旅行时插值算法与最短路径算法,提出了一种三维初至波射线追踪算法。通过对双线性旅行时插值算法进行改进,并运用判定条件与简化插值计算公式进行快速计算,减少了插值次数,降低了运算量,同时也保证了较高的射线精度,有效地解决了三维射线追踪算法的计算低效率,射线精度不高的问题。     

һ��GPS/������ϻ��߽������ģ�͵�ȷ������

??????GPS/??????????????λ????????????????Helmert????????????????????GPS/????????????????????????????????????÷???????????????????????????     

������С����ƽ�����������

???t??????????ó?????????С????????????????????????????????1????????????????????????2????????????????????????????????????????????Э????????????????1??Э??????????????????????????????????????????????????????????????????????????????????????????????????????????????Ч???     

���ڷ���������Ƶĸ߾��ȹ�ҵ����������վ

???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????÷????????????????????????????     

GPS/BDS组合系统伪距单点定位模型精度分析

合理确定观测值权阵对于应用GPS/BDS组合系统提高单点定位的精度和稳定性十分重要.文章对GPS/BDS常用的几种定权模型等权模型、高度角随机模型、基于Helmert验后方差估计模型、顾及PDOP值的定权模型等进行了实验与分析.结果表明:基于Helmert的定权方法精度最高,进一步对其观测值的分类根据高度角进行改进并利用PDOP值的选星思想后,模型精度再次提高.研究结果可以为提高GPS/BDS组合系统伪距单点定位的精度提供参考.     

地铁隧道结构变形监测控制网及其数据处理

由于地铁隧道结构变形监测控制网的特殊性,在变形数据处理过程中基准点稳定性判断是不容忽视的环节,通常稳定性判断是在室内数据处理时进行,为了优化变形数据处理过程,本文采用已有组合后验方差检验法进行基准点稳定性检验,并验证该方法的可靠性,在此基础上提出灵敏度的概念,即检验观测值出现多大变动时能被该方法检测出来,并测试出组合后验方差检验法的灵敏度。通过灵敏度的研究和应用可以现场进行稳定性分析,指导外业变形监测工作,提高观测结果利用率和数据处理效率。     

加权方差分析及其在地壳垂直运动中的应用

经典最小二乘准则下的方差分析要求观测值的正态随机误差之间是相互独立的，而实际遇到的测量数据经常并不满足这一条件。为了从广泛意义上更科学地研究和应用方差分析这一理论，提出了加权方差理论，导出和论证了相应的公式，并以实例讨论了它在地壳垂直运动分析中的应用。