佘山地震台地磁模拟、数字观测资料的对比分析

对佘山地震台地磁数字化观测资料和模拟观测资料D、H、Z等地磁要素日变形态、日均值、月均值、年均值进行了较详细的分析比较,阐述了数字观测系统与模拟观测系统的特点。探讨了磁场剧烈扰动对数字观测系统和模拟观测系统的影响。对做好地磁数字化观测工作,提高地磁资料的观测质量有一定参考意义。     

差分GPS在中国地磁监测网地理方位角测量中的应用

中国地磁监测网由地磁台站和流动地磁测点构成,实现对观测网内地磁场的相对记录和绝对观测。它的绝对观测采用世界上最先进的F、D、I测量仪器组合,其中地磁偏角D是地理北和地磁北的夹角。对地磁偏角D的绝对测量要求在地磁台站投入正常观测前必须完成观测墩和观测标志的地理方位角测量,流动地磁测点在每次地磁偏角D观测前后至少进行地理方位角测量各一次。据地磁监测网《观测规范》要求,地磁偏角D的观测精度必须≤6″,所以中国地磁监测网采用天文和差分GPS地理方位角两种测量方法,且两种方法观测精度相当,均≤6″。与天文测量相比,差分GPS观测不受天气等自然因素的限制,操作简单,观测快捷,数据处理计算机程序化。随着GPS技术的普及,中国地磁监测网差分GPS地理方位角测量方法已基本取代了天文方法。本文主要介绍差分GPS在中国地磁监测网地理方位角测量中的应用。     

地磁观测中电磁干扰测定及抑制措施初探

以黄壁庄地震台地磁观测为对象,通过实验测定外界电磁干扰对FHD地磁观测的影响,采取对供电线路加接地、重新布设观测信号线、停用稳压电源等方法,使FHD地磁观测的F、H、D、Z数据精度均有显著提高,明显改善了地磁观测数据的质量和精度。     

北京地磁台的磁环境监测

对北京地磁台建台以来,台站周边环境随着北京城市化进程发生的变化做了较详细的描述.利用几次在台站地磁观测区范围内的地磁场梯度观测资料,分析了台站地磁观测场地磁场梯度的变化情况,并对现有地磁场梯度环境进行了评估.为北京地磁台及全国其他台站,在现有条件下的地磁观测工作提供了有益的参考.     

佘山白水营两地磁台历史概况与观测资料比较及若干问题分析

(1 回顾整理佘山与白水营地磁台历史概况及其观测资料,比较分析其磁倾角和磁偏角长年变化趋势大致相同,反映了地磁场长期变化现象.随着时间推移,研究分析历史地磁资料显得有其独特意义.不少地磁台观测环境受到干扰破坏,甚至新建地磁台观测也受到某些干扰影响,历史地磁观测资料对地震电磁学研究更显得可贵.     

高压直流输电对地磁观测影响的特征分析

越来越多的高压直流(HVDC)输电工程在全国范围内投入运行,对地磁观测造成了较大.范围的干扰,这种干扰需要观测员进行数据预处理,以便产出可靠的地磁观测资料。本文通过对HVDC运行的故障特性、地磁台站与高压直流线路的相对位置以及对地磁观测资料造成的干扰形态进行分析,指出了HVDC对地磁观测造成的4个干扰特性,为识别、判定这种干扰提供了依据。     

高压直流输电线对甘肃地磁观测的影响分析及应对措施

随着国家电网建设规模的不断扩大,越来越多的高压直流输电工程陆续投入使用,对线路两侧的地磁观测资料造成了不可避免的影响。目前有5条高压直流输电线路对甘肃地磁台站的观测造成一定程度的干扰。通过单台及多台观测资料对比的方法,识别高压直流输电线对地磁观测资料的影响,研究干扰特征,对正确预处理观测资料有重要的意义。结果表明:①高压直流输电对地磁Z分量影响明显,D、H分量不明显;②对地磁观测影响产生的形态主要表现为方波型、缓变型、梯形型、复合型等。通过总结高压直流输电对地磁观测资料影响特征及形态,有助于正确预处理观测资料及为今后实现计算机自动化处理提供依据。     

关于数字地磁台站观测系统的发展与观测资料应用的一点思考

针对地球科学和国家建设对地磁观测与研究的需求，结合“九五”地磁台站观测技术数字化改造，对地磁台站观测系统的发展及数字观测资料的应用提出了一些见解。     

山西定襄地震台发电干扰地磁观测数据的原因及排除方法

在定襄地震台地磁观测中,地磁仪易受到发电机的供电干扰,文章通过对观测数据的分析,进一步找出干扰的原因,并提出排除方法。同时,对影响地磁观测的其他因素进行分析,以提高地磁观测资料的精度,保证仪器运行的稳定性。     

2013年吉林松原M5.8地震震前地磁异常分析

应用东北地区地磁观测台站地磁总场强度整点值观测数据,利用每日一值相关法和差值法;应用地磁垂直分量日变幅观测数据,利用加卸载响应比和逐日比方法,分析地磁总场强度F分量、垂直Z分量与吉林省松原M5.8地震应震关系,分析上述方法对提取地磁观测数据震前异常信息的有效性。     

A Monte Carlo study of rainfall forecasting with a stochastic model

A procedure for short-term rainfall forecasting in real-time is developed and a study of the role of sampling on forecast ability is conducted. Ground level rainfall fields are forecasted using a stochastic space-time rainfall model in state-space form. Updating of the rainfall field in real-time is accomplished using a distributed parameter Kalman filter to optimally combine measurement information and forecast model estimates. The influence of sampling density on forecast accuracy is evaluated using a series of a simulated rainfall events generated with the same stochastic rainfall model. Sampling was conducted at five different network spatial densities. The results quantify the influence of sampling network density on real-time rainfall field forecasting. Statistical analyses of the rainfall field residuals illustrate improvement in one hour lead time forecasts at higher measurement densities.     

Information for authors

正SCIENCE CHINA Earth Sciences,an academic journal cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China,and published by Science China Press and Springer,is committed to publishing high-quality,original results in both basic and applied research.     

INTERNATIONAL RESEARCH AND TRAINING CENTER ON EROSION AND SEDIMENTATION(IRTCES)

正Director:Shangfu Kuang,China Vice-directors:Chunhong Hu,China Duihu Ning,China Guangquan Liu,China The International Research and Training Center on Erosion and Sedimentation(IRTCES)was jointly set up by the Government of China and UNESCO on July 21,1984.It aims at the promotion of international exchange of knowledge and cooperation in the studies of erosion and     

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Dynamic process-response model of river channel development

Feedback mechanisms, which operate upstream through drawdown and backwater effects and downstream through sediment discharge are responsible for channel evolution. By combining these mechanisms with channel processes it euables a dynamic process-response model to be developed to simulate the initial evolution of straight gravel-bed channels. When erosion commences on a land surface, sediment entrained in the headwater reach by hydraulic action is selectively transported, deposited and reworked. This produces a damped oscillation between degradation and aggradation as the channel and valley respond to spatial and temporal variations in sediment calibre and hydraulic conditions. The initial cut and fill phases are responsible for valley incision and floodplain development while secondary and subsequent activity can produce river terraces. Eventually sediment entrainment in the headwaters declines as slopes are reduced. Subsequent channel evolution is relatively insignificant because it is dependent on local weathering activity producing material that can be transported on declining slopes. Therefore landforms produced during the initial phase of development, when local weathering was non-limiting, dominate the landscape.