Phase-array decomposition of a seismic section

A seismic re fraction/wide-angle reflection profile is analysed for the presence of correlated events ('phases'). The correlation problem is formulated in terms of temporally, spatially and frequency-local complex covariances. For robustness, the method concentrates on phase rather than amplitude information. This allows a computationally efficient algorithm that can make allowance for signal correlation length and can model curved wavefronts. A statistical test based on residual phase misfit across the analysed subarray is used to assess the probability that a detected event represents a real correlated signal.
With our chosen analysis parameters and confidence level (over 99.9 per cent). 1222 events were detected in the data. Using simple techniques based on 1-D earth models, detected events are associated with a small number of particular wave types. In this way, we have succeeded in classifying almost 95 per cent of the detected events. Those that remain describe those components of the data that are inconsistent with our simple ray paths in the 1-D assumption and with our prescribed tolerance. These include reverberations, near-surface guided waves and reflected waves from strongly laterally inhomogeneous structures. According to our modelling, about 25 per cent of the detected events are consistent with simple P -wave reflected energy, and these are to a very large extent (over 85 per cent) distinct from all the other wave-type models we have used. A direct mapping of the detected events into the offset-depth domain reveals dear internal and external consistencies among the detections for the various wave types. Estimated earth structure is consistent with models from previous analyses based on much larger data sets.
We have thus succeeded in extracting correlated events from the data and decomposing these, approximately but meaningfully, into distinct classes (ray paths)     

Noise reduction and detection of weak, coherent signals through phase-weighted stacks

We present a new tool for efficient incoherent noise reduction for array data employing complex trace analysis. An amplitude-unbiased coherency measure is designed based on the instantaneous phase, which is used to weight the samples of an ordinary, linear stack. The result is called the phase-weighted stack (PWS) and is cleaned from incoherent noise. PWS thus permits detection of weak but coherent arrivals. The method presented can easily be extended to phase-weighted cross-correlations or be applied in the τ p domain. We illustrate and discuss the advantages and disadvantages of PWS in comparison with other coherency measures and present examples. We further show that our non-linear stacking technique enables us to detect a weak lower-mantle P -to- S conversion from a depth of approximately 840 km on array data. Hints of an 840 km discontinuity have been reported; however, such a discontinuity is not yet established due to the lack of further evidence.     

The Organization of Production in High Technology Industries: An Empirical Assessment*

Recent attention given to the concept of vertical integration and disintegration of production processes has identified the existence of a continuum, with small, flexibly specialized producers at one end and large, mass production units at the other end. Firms along the continuum constantly strive for the optimum combination of economies of scale and scope. This paper attempts to identify the organizational characteristics of high technology firms in one industrial complex of the U.S. Manufacturing Belt. A principal components analysis is performed on a number of theoretically relevant variables for a sample of high technology establishments in Northeast Ohio. The results indicate that the region contains a variety of organizational forms ranging from isolated workshops to large, vertically integrated assembly plants. These findings conform to expectations derived from recent conceptualizations in the literature. Additional empirical research will further enhance understanding of the processes that shape the organization of production in territorial complexes.     

Site effects at a vertical accelerometer array near Paducah, Kentucky

The downhole vertical accelerometer array VSAP near Paducah, KY, consists of three-component accelerometers at the surface, the top of the McNairy Formation (−41 m), and the top of the Paleozoic bedrock (—99 m). The array is at the northern end of the Mississippi Embayment, and it was installed to verify the ground-motion modeling for the site, assuming a significant earthquake in the New Madrid Seismic Zone. Accelerograms from 4.2 and 2.0 m_b earthquakes were used to check aspects of the modeling pertaining to linear behavior of the soil column, and to review the soil column models derived by drilling and geotechnical methods and through the use of high-resolution P- and SH-wave seismic refraction in reflection techniques. Results of the study indicate that for the linear case the soil column models derived by the two techniques are equivalent, and that the most important boundary in the soil column, with respect to amplification of the ground motions, is the interface between the limestone bedrock and soil.     

计算机多媒体技术在地学领域中的某些应用

结合地质工作特点，概述了计算机多媒体技术在地质科研、地质教育、成果汇报演示以及地质信息管理方面的应用成果，展示了多媒体技术在地学领域中的应用前景。     

对企业信息化建设的认识

本文简要介绍了企业信息化的概念、内容及实现企业信息化的关键技术 ;阐述了企业信息化建设过程中应注意的问题 ,认为应坚持从企业实际出发 ,进行整体规划 ,注意开发和利用并重 ,使信息化适合企业个性化需求。     

后遥感应用技术研究与地质实践——以东胜—神木地区铀资源勘查为例

介绍了后遥感应用技术提出的背景及技术构成,阐述了该技术的研究内容及取得的地质成果。实践表明,在地质勘查领域,后遥感应用技术比单一遥感技术具有更大的实用价值和更好的应用效果。     

地震资料曲流河辫状河油气储层识别与预测

曲流河、辫状河储层在我国的陆相盆地中广泛分布。由于曲流河相沉积砂体的单层薄、横向变化；辫状河相沉积的砂体迁移快、垂向加积等特点，增加了在勘探过程中对其分辨的难度。因此，对地震资料曲流河、辫状河油气储层的识别与预测，必须综合多种与其相关的地质资料，结合地震数据体中给出的信息来判断分析，以达到提高分辨率的目的。     

枯水研究进展

枯水和洪水是水文学中极值范畴,自20世纪七八十年代以来,大规模地开展河流枯水研究工作,但枯水研究的深度远远低于洪水。总结前人研究的成果可以发现,人类对枯水研究的内容主要集中在以下3点:①对不同区域影响枯水的主要因素进行识别;②枯水频率分析以及有关枯水资料的处理方法;③分析枯水径流的计算方法及系统预测。从研究方法来看,过去,对于枯水研究中所采用的方法主要是以概率统计学和时间序列分析等为主的传统方法。随着信息时代的到来,一些新的技术、新的方法纷纷地应用于枯水研究,如"3S"技术(RS、GIS、GPS)。通过枯水研究综述,对我国进一步开展枯水研究以及合理利用枯水资源提供了科学依据,为我国开展系统综合分析应用研究,特别是对西部的干旱、半干旱地区具有深远的科学现实意义。     

地理信息技术的发展与应用

地理信息系统是国家信息资源的重要组成部分。地理信息技术经过20多年的飞速发展，已经渗透到社会各个方面，促使人们生产、生活方式发生深刻变化。我国地理信息系统(GIS)技术正在向信息化方向发展，并正在逐步成为面向21世纪的支柱产业一信息产业的重要组成部分。国际GIS技术的发展趋势，主要体现在两个方面，一是综合，二是分化。从空间信息处理的角度看，可将GIS的发展分为空间信息的管理、分析、模拟和调控四个阶段。GIS技术的应用表现在一是面向大型项目，二是面向公众。