Geostatistical Analysis of Inverse Problem Variables: Application to Seismic Tomography     

Juan L. Fernández Martínez  César O. Menéndez Pérez  Luis M. Pedruelo González  José P. Fernández Alvarez  Pablo Cienfuegos Suárez 《Mathematical Geology》2003,35(8):953-969

In this article we present a geostatistical approach to the transmission tomographic inverse problem, which is based on consideration of the inverse problem variables (velocity and traveltime errors) as regionalized variables (R.V.). Their structural analysis provides us with a new method to study the geophysical anisotropy of the rock, an important source of a priori information in order to design the anisotropic corrections. The underlying idea is that the geophysical structure can be deduced from the spatial structure of the regionalized variables which result from solving the tomographic problem with an isotropic algorithm. Also, the application of the structural analysis technique to the anisotropic corrected velocity field allows us to characterize the reliability of these corrections (model quality analysis). Geostatistical formalism also provides us with different techniques (parametric and non-parametric) to estimate and even simulate the velocity in the areas where this field has been considered anomalous based on field studies and on geophysical and statistical criteria. The kriging acts as a low-pass smoothing filter for the anomalous model parameters (velocities), but is not a substitute for an adequate filtering of the outliers before the inversion. This methodology opens the possibility of considering the inverse problem variables as stochastic processes, an important feature in cases where the tomogram is to be used as a tool of assessment to quantify the rock heterogeneities.  相似文献   

Radio Tomography: A New Experimental Technique   总被引：2，自引：0，他引：2  

S. E. Pryse 《Surveys in Geophysics》2003,24(1):1-38

The technique of radio tomography has developed during the past fifteen years from a theoretical concept to an established experimental method, used for geophysical investigations ofsolar-terrestrial processes. It also has potential in the mapping and modelling of the ionised atmosphere for application to practical radio systems. The method involves measurement of the electron content of the ionosphere along a large number of intersecting satellite-to-receiver ray paths, with tomographic inversion of the data to give a two-dimensional image of the spatial distribution of plasma density in the region of ray-path intersection. The emphasis in this review is on experimental tomographic observations, which have highlighted the capabilities and potential of the technique. Examples are presented from the equatorial sector where the equatorial anomaly is a significant feature, the mid-latitude sector where radio propagation is often influenced by the presence of the main ionisation trough, and the auroral and polar regions where footprints of solar-terrestrial coupling processes are frequently to be seen.  相似文献   

L ateral Variation of Pn velocity beneath northeastern marginal region of Qinghai—Xizang plateau   总被引：1，自引：0，他引：1  

许忠淮  汪素云  裴顺平 《地震学报(英文版)》2003,16(1):26-33

Pn arrival time data are collected from the bulletins of both national and regional seismological network in China-These data are tomographically inverted to map the lateral variation and anisotropy of Pn velocity in the northeast-ern marginal region of Qinghai-Xizang plateau.The average Pn velocity in this region is 8.09km/s,being a little higher than the average for whole China,Higher velocity is found in tectonically stable Qaidam basin,while lower velocity is seen in and around tectonically active Shanxi graben.The region where the 1920 Haiyuan great earth-quake occurred shows a slightly low Pn velocity.A noticeable result is that,differing from the tectonically com-pressive Tianshan region.where Pn velocity is low,the Qilianshan region,where the Neotectonic deformation is also primarily compressive,shows high Pn velocity,In the uppermost mantle beneath the Ordos plateau Pn veloc-ity is inhomogeneous,varying from higher velocity in southwestern part to lower one in northeastern part.This may be attributed to possible movement of the Ordos block,as there are strong earthquakes all around the block.  相似文献   

Tomographic investigation of the upper crustal structure and seismotectonic envi—ronments in Yunnan Province   总被引：1，自引：0，他引：1  

白志明  王椿镛 《地震学报(英文版)》2003,16(2):127-139

Investigation has been made for the upper crust structure and seismotectionic environments in Yunnan Province using the plentiful DSS data of the four profiles.The derived velocity model has a good relationship with the ex-posed basins,uplifts and faults.The low velocity anomaly corresponding to the volcano also has been revealed.There exits a prominent lateral inhomogeneity within the upper crust of Yunnan region.The depth of crystalline basement generally ranges from 0km to 5km,and the bedrocks are exposed on the ground directly in some places,nevertheless the thickness of sedimentary cover also can reack to 8km or even 12km at some targe depressions.Although the Changning-Shuangjiang fault is a boundary between two first class tectonic units,its incision depth within the crust maybe shallow.On the other hand,known as the plates‘seam,the Honghe fault has a distinct evi-dence of extending into the mid-lower crust.The widely spread activity of the volcanoes in the geological era has a close relationship with the earthquake‘s occurrence nowadays.Despite of the ceasing of the volcanoes in some places on the ground,the material in the mid-lower crst is still active,and there still exists strong upward stress-As the ceasing of the volcanoes on the surface,most parts of the power from the lower crust and the upper mantle cannot be released;therefore it accumulates at some appropriate tectonic locations.Moreover,the saturation of the water from the basin,the action of other fluids,and the effects of the outer stress maybe another direct reason ac-count for the strong earthquakes‘occurrence in Yunnan region.  相似文献   

Crosshole ultrasonic tomography and its application to karst investigation   总被引：1，自引：0，他引：1  

刘红桂  刘建达  许汉刚  宋文荣 《地震学报(英文版)》2003,16(4):441-448

Crosshole ultrasonic tomography is referred to ray tracing by gilding method and image reconstruction by combining the successively linearized iteration with damping least-squares QR decomposition, with which the result has better precision than that with crosshole seismic tomography by using the same inversion method in engineering geological investigation. It has been proved in practice that the investigation with crosshole ultrasonic tomography can clearly show the location and shape of the abnormal geological unit with the volume more than 60 cm when the crosshole distance exceeds 30 m. The result of investigation has been confirmed by the drilling. The crosshole ultrasonic tomography method will be extensively used in the engineering geological investigation.  相似文献   

CT对乳腺癌的诊断探讨     

陈义辉  黄福气  陈钦 《CT理论与应用研究》2003,12(1):24-26

目的 探讨乳腺癌CT检查的技术特点和影像学特性，提高对乳腺癌的诊断水平。方法 对23例经手术后病理证实的乳腺癌病例，进行回顾分析。结果 CT扫描能清晰显示乳腺解剖结构，对病灶显示的阳性率高；CT扫描及增强扫描能显示病灶大小及周围的情况。结论 CT扫描及增强扫描对乳腺癌的诊断与鉴别诊断有较高价值，有助于临床TNM分期及制定治疗计划，是乳腺癌较好的检查方法。  相似文献   

铸件的工业CT三维检测技术   总被引：2，自引：0，他引：2  

曹玉玲  陈存柱 《CT理论与应用研究》2003,12(3):36-39

通过对工业CT扫描得到的连续二维图片进行三维重建，得到试件的三维重建图像，从而可用于复杂构件的三维结构分析、缺陷硷测，并可与快速成型系统相结合，实现对复杂零件的快速复制，在产品开发及制造过程中起到了重要作用。  相似文献   

2003年国际地球物理大会对于地球断面成像和灾害预测的某些论述     

《CT理论与应用研究》编辑部 《CT理论与应用研究》2003,12(4):49-52

目的: 通过2003年国际地球物理大会(IUGG)了解国际上关于地球断面成像和灾害预测的某些主流的信息,向读者提供前缘信息. 资料和方法:本文所概括和摘录的信息来自 2003 IUGG Program & Abstracts 光盘, 选择其与本刊密切有关的内容供交流.结论:火山喷发与洪水的预测可以为预测地震有所借鉴;对于地下物理参数的三维探测,成像演示,其分辨率的增加会引起预报模型发生质的变化,利用高精度的三维速度结构以改进火山的预测工作.  相似文献   

云南及周边地区Lg尾波Q值的分布特征   总被引：11，自引：6，他引：11       下载免费PDF全文

胡家富  丛连理  苏有锦  康国发 《地球物理学报》2003,46(6):809-813

收集了昆明台1990～2000年间大于4.0级的地震宽频记录资料，以及分布在云南境内的23个昆明数字化台网1999～2000年的资料，使用单台叠加谱比方法处理了280个Lg尾波信号. 在假定Lg尾波Q与频率f有Q =Q0fη关系的基础上，计算出各射线1Hz时的Q值及频率相关因子η. 在此基础上，运用反投影技术反演得到云南及周边地区0.5°×0.5°网格内的Q0和η的分布图像. 结果表明：云南及周边地区的Q0在150～300之间变化，滇东地区的Q0明显高于滇西地区；η的变化范围在0.3～0.8之间，绝大部分地区η的变化范围为0.5～0.6.  相似文献   

地震层析成像中存在的主要问题及应对策略   总被引：10，自引：10，他引：10  

成谷  马在田  张宝金  耿建华  曹景忠 《地球物理学进展》2003,18(3):512-518

详细讨论了地震层析成像中存在的主要问题，包括数据投影角度不全、数据不均匀覆盖、反射层析中界面深度和速度的耦合、参考模型引起的非线性误差问题、边界作用、数据的不确定性和模型参数不同分量的不确定性不同。分析了问题的产生原因和应对策略，并给出了在层析反演过程中应该注意的一些控制措施。  相似文献