Application of a Global 3D Model to Improve Regional Event Locations

Accurate location of weak seismic events is crucial for monitoring clandestine nuclear tests, for studying local seismic structures, and for assessing possible seismic hazards. Outside of a few regions with dense seismic networks, weak seismic events (with magnitude less than 4) are usually sparsely recorded at epicentral distances less than 20°. Because of lateral variations in crustal and upper mantle structures, observed travel times of seismic phases deviate significantly from predictions based on 1-dimensional (1D) seismic models. Accurately locating weak seismic events remains a difficult task for modern seismology. Perhaps the most promising solution to this problem is the use of a 3-dimensional (3D) model of the Earth. Here we present the results of a validation test in which, using the 3D model SR2002 of the crust and upper mantle and regional phase data alone, we relocate 200 earthquakes and nuclear explosions in Eurasia. The 3D model is constructed using surface wave dispersion data. The event locations using the 3D model are compared with so-called Ground Truth data, either known by non-seismic means or validated by cluster analysis, with location accuracy mostly 5 km or better. Typically, the 3D model reduces the location errors to about half the values attained with the 1D model; i.e., 18 km location errors are reduced to about 9 km. This test indicates that the location of regional events can be significantly improved by using a global 3D model.     

基于参照点的任意区域检测方法

区域检测，即判定当前点是否位于某个已知的区域之内，这是电子地图处理和计算机图形学以及目标定位中经常遇到的问题。对于任意区域的检测目前尚无很满意的方法，文中给出的基于参照点的检测方法，思路清晰、实现简便，且适用3维空间任意区域的检测。     

移动式GIS发展的关键技术及应用前景

GIS发展的最终目的是使GIS平民化，而移动式GIS的快速发展使GIS能真正进入百姓生活。移动式GIS是GIS真正融入主流IT技术并与现代通信技术、GPS技术相结合的产物，通过对移动式GIS发展的关键技术进行分析，并对未来移动式GIS的应用进行了预测。     

云南东部地区近期大震危险性地点分析

金沙江—红河断裂是一条超地壳大断裂，为云南地区重要的构造边界，把云南地区划分为东、西两个部分。本简要介绍了云南东部地区主要活动断裂的活动性质，结合发震构造标志、地震破裂围空特征和大震重复周期等分析了红河断裂以东(含红河断裂带)地区的大震危险性，认为云南东部地区近期大震的危险地点有2个：小江断裂中段东支和石屏—建水断裂带石屏以东地区。     

区域空间结构重组理论初探

区域空间结构重组是经济社会转型时期重要的区域结构调整任务之一。新一轮的空间结构重组需要澄清三大理论问题：一是空间结构的历史特征与未来景观；二是区域发展与空间结构重组的相互关系；三是区域产业结构调整与空间结构重组的相互关系。同时，在经济全球化和新经济快速发展的变局下，需要探索新的空间结构重组理论指导区域空间结构重组的实践。该文根据区域空间结构重组理论，分析新时期长江流域的空间结构重组要点。     

外部规模经济与国际贸易区域化及其对中国的启示

在世界贸易格局的形成中，贸易区域化现象引人注目。文章运用外部规模经济理论对这种现象予以新的解释，即在世界经济一体化浪潮中，一些地理位置邻近、文化背景相似的国家为获取有利的贸易区位，通过产业分工、对内合作和对外竞争形成区域贸易集团，并由此产生“区域外部规模经济”。作者认为，为获得有利的贸易区位和区域外部规模经济，中国一方面要加强与国际贸易区域组织的合作，另一方面要加强次区域及国内地区间的合作。     

德国大陆超深钻井注水诱发地震的精确定位

2000年8月21日～10月20日，德国大陆超深钻井(KTB)进行了为期60天的新一轮注水诱发地震实验．在对KTB台网所记录到的2 700多次地震的原始波形进行分析和处理的基础上，对其中的237次地震进行了精确定位．定位时，先采用和达法剔除了误识的非KTB诱发地震事件；然后，使用大折刀法求得了台站偏差的最佳值，以及中误差和平均误差；最后应用Geiger法进行修定，从而保证了237个事件定位的中误差达到0.1 km的高精度．定位结果显示，在大于9.3 km(几乎是主井底的深度)没有发生诱发地震．这一现象表明，在这个深度，应力可能低于摩擦强度，以至于由注水引起的孔隙压力的变化不足以诱发地震；在这样的深度不存在可渗透的、取向恰当的断层．这个深度也可能是这一区域内的地震活动性的最大深度，即在这一相对稳定地区的板块内部，主井底已接近脆-延性转换带．并用实验室的结果和超深钻井中所观测到的热流值资料解释了这一现象．      

用于地震定位的SAMS方法

由于地震定位受发震时刻与震源深度间强烈的折衷关系的困扰及反演问题的非线性影响,该问题一直未得到根本解决. 为此,本文提出了一种新的定位方法--SAMS法,该方法利用走时残差和到时残差之绝对值极小作为目标函数,用快速模拟退火法求解反演问题的解答. 并将该方法用于1999年9月21日台湾集集地震的再定位,其结果与其他方法相比,SAMS方法不仅降低了发震时刻与震源深度间的折衷关系对定位结果的影响,而且其定位结果具有很高的稳定性和分辨率.     

遥测台网的震相分析

遥测地震台网要给出较好的地震定位结果，需要正确地判断各类震相，总结提高快速处理方法，使地震分析和速报水平不断提高。     

Seismicity of Garfagnana-Lunigiana (Tuscany, Italy) as recorded by a network of semi-broad-band instruments

Eight seismic stations equipped with5-second sensors have recently beeninstalled in the Lunigiana-Garfagnana areato monitor activity in this sector of theNorthern Apennines shaken by the 5.0 Mdearthquake of October 1995. The stations(RSLG network) represent an eastern branchof the RSNI (Regional Seismic network ofNorthwestern Italy) managed by Dipteris,Universita' di Genova.The installation of this dense networkallowed the operators to improve themagnitude detection level, providinginformation about the seismicity of thearea down to magnitude 1.0. Severalanalyses have been carried out to evaluatethe performance of the network and thereliability of the computed locations. Itseems that the epicentral location forevents occurring inside the network isalready constrained using 8–10 P+S phases,but usage of more readings ensuresreliability of depth and the reduction oflocation errors.Though not conclusive, as the network hasonly been fully operating for two years, apreliminary study carried out on a selecteddataset of high-quality locations confirmed that the seismicity of theGarfagnana-Lunigiana is characterised by alow-to-medium magnitude level and it issubdivided into two bands, a superficialone about 30–35 km thick and the secondbelow 50 km. This distribution, confirmedby other studies carried out in the past,reflects the complex structure of this areawhere two tectonic plates (European andAdriatic) meet.