The information content of high-frequency seismograms and the near-surface geologic structure of “hard rock” recording sites

Due to hardware developments in the last decade, the high-frequency end of the frequency band of seismic waves analyzed for source mechanisms has been extended into the audio-frequency range (>20 Hz). In principle, the short wavelengths corresponding to these frequencies can provide information about the details of seismic sources, but in fact, much of the signal is the site response of the nearsurface. Several examples of waveform data recorded at hard rock sites, which are generally assumed to have a flat transfer function, are presented to demonstrate the severe signal distortions, includingf _max, produced by near-surface structures. Analysis of the geology of a number of sites indicates that the overall attenuation of high-frequency (>1 Hz) seismic waves is controlled by the whole-path-Q between source and receiver but the presence of distinctf _max site resonance peaks is controlled by the nature of the surface layer and the underlying near-surface structure. Models of vertical decoupling of the surface and nearsurface and horizontal decoupling of adjacent sites on hard rock outcrops are proposed and their behaviour is compared to the observations of hard rock site response. The upper bound to the frequency band of the seismic waves that contain significant source information which can be deconvolved from a site response or an array response is discussed in terms off _max and the correlation of waveform distortion with the outcrop-scale geologic structure of hard rock sites. It is concluded that although the velocity structures of hard rock sites, unlike those of alluvium sites, allow some audio-frequency seismic energy to propagate to the surface, the resulting signals are a highly distorted, limited subset of the source spectra.     

电阻抗层析成像的电导网络解法

阻抗ＣＴ技术是通过在物体的边界进行一些电测量来重建内部阻抗分布。本文提出利用网络理论来解决阻抗ＣＴ的一种新的重建方法。首先将非均匀电导分布区域离散化为具有一些节点的电导网络，然后在边界节点上施加一组正交的电流激励，测量感生出的电压。根据网络论，这样就可利用网络的节点方程来进行求解．为求得最符合观测值的节点电导矩阵Ｇ的估计，我们从Ｇ的性质中提取了两类约束，根据广义投影理论，采用施加约束的迭代方法来重建这一反映电导分布的节点电导矩阵Ｇ．计算机模拟表明，迭代是收敛的并且能得到较好的重建结果。     

滇西南地区五年内大震形势预测

本文采用极值理论、线性预测和最大熵谱分析三种不同的概率统计预报方法，从不同的角度对滇西南地区地震活动进行研究，得到滇西南５年内将有１次６．５－６．９级地震活动，１９９２年有６．０－６．４级发震可能的中短期预报结果。     

数理统计方法在区域地球物理资料构造分区中之应用

本文介绍了利用小比例尺重磁资科进行构造分区的数理统计方法。讨论了分区中的单元划分及变量组合等问题,提出了单元划分的原则及各类变量在分区中的作用。最后,利用辽宁及新疆的资料作了统计分区,取得了较为满意的结果。     

应用遥感信息复合方法的森林分类和动态监测研究

在森林资源清查和动态监测中，一般要求能识别树种、在树种复杂时也要求识别到树种组。成图时要求可直接使用几何精度高、类型边界清晰的中比例尺如１：２．５万的影像图。为了满足生产的需要，我们进行了遥感信息复合、遥感与非遥感信息复合及复合方法等实用技术应用的研究。实验中应用了ＭＳＳ与ＴＭ卫星图像、ＴＭ不同时相的图像、ＴＭ与Ｓｐｏｔ的复合，及复合前后信息特征变化的定量分析等研究。从而为最优波段组合、特征信息提取方法提供了基础。在动态分析中主要进行了采伐迹地、林墙、迹地更新等方面的测定，并对测定精度进行了评估。     

土地信息系统建立过程中的数据质量问题

数据是信息的载体,数据对土地信息系统(LIS)来说是至关重要的,数据质量的好坏是土地信息系统建设成败的关键。信息系统对数据进行处理就是为了得到数据中所包含的信息。本文将对土地信息系统建立过程中有关数据质量问题进行探讨。     

浅谈中国石油天然气集团公司(CNODC)海外数字油田与勘探开发一体化集成系统的建设

本文就中国石油天然气集团公司CNPC海外业务成功运作实践，指出数字油田技术可望成为中石油在国际市场竞争中的利器.随着海外业务的快速发展，作业的国家及相关项目迅速增加，随之而来的项目管理、经营调度、生产监控等公司日常管理工作日趋复杂，相关信息往来越来越多、传递速度越来越快.与此同时，信息技术的迅猛发展，为实现企业的海量信息处理需求提供了可能，而连接海内外的数字油田建设正是提高公司核心竞争力的重要载体和手段.论述了CNODC海内外项目的信息化现状及存在问题，指出勘探开发一体化集成系统建设作为核心技术是海外数字油田的重中之重，呼吁尽快提出适合自己的高效、规避风险的与海外项目紧密连接的“海外数字油田”战略.     

A Moore's cellular automaton model to get probabilistic seismic hazard maps for different magnitude releases: A case study for Greece

Cellular automata are simple mathematical idealizations of natural systems and they supply useful models for many investigations in natural science. Examples include sandpile models, forest fire models, and slider block models used in seismology. In the present paper, they have been used for establishing temporal relations between the energy releases of the seismic events that occurred in neighboring parts of the crust. The catalogue is divided into time intervals, and the region is divided into cells which are declared active or inactive by means of a threshold energy release criterion. Thus, a pattern of active and inactive cells which evolves over time is determined. A stochastic cellular automaton is constructed starting with these patterns, in order to simulate their spatio-temporal evolution, by supposing a Moore's neighborhood interaction between the cells. The best model is chosen by maximizing the mutual information between the past and the future states. Finally, a Probabilistic Seismic Hazard Map is given for the different energy releases considered. The method has been applied to the Greece catalogue from 1900 to 1999. The Probabilistic Seismic Hazard Maps for energies corresponding to m = 4 and m = 5 are close to the real seismicity after the data in that area, and they correspond to a background seismicity in the whole area. This background seismicity seems to cover the whole area in periods of around 25–50 years. The optimum cell size is in agreement with other studies; for m > 6 the optimum area increases according to the threshold of clear spatial resolution, and the active cells are not so clustered. The results are coherent with other hazard studies in the zone and with the seismicity recorded after the data set, as well as provide an interaction model which points out the large scale nature of the earthquake occurrence.     

网络环境下地震科技信息管理初探

针对当前计算机网络的特点,从地震科技信息介质的转变,资源的开发、利用,管理、保障体系的完善,服务方式的改变等方面进行了论述,指出,要充分利用网络资源,使地震科技信息更及时、准确、全面地为防震减灾事业服务。     

广东省基础地理信息数据库的应用及设想

基础地理信息数据库是我国要建立的四大数据库中的重要内容,各省均相继开展或完成了省级基础地理信息数据库的建设。数据库建成后,如何高效和安全地使用数据库,广泛服务于社会,是当前面临的重要问题。本文结合数据库的建设现状,从实际需求出发,在实践中归纳了基础地理信息数据库目前及未来应用的设想。