福建地震台网"十五"与"九五"观测系统测定震级对比分析

利用福建"九五"地震台网和"十五"地震台网的并行条件,对其观测资料的测定位移震级进行对比分析,初步得出二者的位移震级偏差,并分析造成偏差的原因.了解两种观测系统的差异对震级的影响,对测定震级具有参考价值.     

福建泉州台测台湾地震的震级偏差

台湾是地震多发地区 ,5级以上地震年均 5～ 2 0次。 1 999年 9月 2 1日台湾南投 7.6级大地震 ,释放的能量之大、余震之多在该区为百年罕见。截止到 1 1月 1日 ,泉州台共记录可分辨震相的余震近千个 ,其中 5级以上 50多个。通过对 9.2 1地震大量观测数据的对比 ,泉州台测定的 MS震级明显小于全国基本台网的平均震级 ,在一定程度上影响了泉州台对台湾地震速报的准确度 ,甚至有的 5级左右的台湾地震 ,因测算的震级偏小而未能速报。1　涉及台湾地震的几个问题1 .1　地震记录特征泉州台相对台湾的震中距离一般在 30 0 km左右 ,记录震相主要有 P…     

福建地震台网与中国地震台网测定台湾地区地震震级差异分析

选用福建地震台网"十五"观测系统正式运行以来记录的台湾地区M≥4.0地震资料,以中国地震台网给出的震级为标准震级,进行了震级偏差统计分析,初步得出震级校正值。并分析了震级差异形成原因,为福建地震台网测定台湾地震震级偏差改正提供参考。     

陕西数字地震台网子台测定震级的研究

使用陕西数字地震台网1998～2003年间的地震记录,以台网平均震级为标准震级,分析了各子台的测定震级。结果表明,各子台测定震级的偏差存在地域分布特征,震级随方位角显示趋势性变化。台址位于平原和山区交界处的台站,对于山区发生的地震测定震级偏大,对于平原地区发生的地震测定震级偏小。最后对震级偏差成因进行了探讨。     

福建台网速度震级与仿真震级差异分析

选用福建地震台网“十五”观测系统运行以来记录的ML≥1．0地震资料,对测定的速度震级和仿真震级进行了震级偏差统计分析,初步得出两种震级偏差值及相关系数,并分析了震级差异形成原因,为福建地震台网震级的测定提供参考。     

区域数字地震台网近距离面波震级MS的测定

使用福建区域数字台网7个宽带台观测到的47个发生于台湾地区的浅源强震(M_S ≥ 5)的近距离面波记录,量算了水平向乐夫波的最大合成振幅及震中距离,测定了所有这些强震的近距离面波震级MS。并将结果与国家台网公布的远距离平均MS震级进行比较和统计分析。结果表明,近距离测定的面波震级比远距离测定的M_S 有较大偏差。震级越小、距离越近,差异越大。对于区域地震台网测定的M_S 震级,需要做必要的修正,才能使其测定结果尽可能接近于国家台网公布的平均M_S 震级。文中还讨论了近距离和远距离面波震级测定差异的原因,及其修正办法。可供区域数字宽带台网速报本区域发生的近距离强震面波震级时参考。     

多个地震台网相互融合测定震级的贝叶斯算法

流动地震台网由于台站台基响应、震级测定方法和操作方式等多种因素的影响, 测定震级与区域内的固定地震台网震级测量结果存在差异, 从而使其记录到的而标准台网没有记录到的大量局域小地震不能直接补充到标准目录中.即使流动地震台网的震级测定公式中的量规函数经过校正, 两者在具体地震事件的震级测定上的差异仍不可避免, 因此急需解决这一普遍性问题的快速计算方法.本文先假定震级的观测值服从正态分布, 其中对固定台网而言, 测定震级的平均值为未知的真实震级, 对流动台网而言, 测定震级的平均值为真实震级的一个线性函数, 然后基于贝叶斯原理, 推导得出了不同台网观测震级的后验概率密度函数.应用于实际观测资料时, 可用最大似然估计来获得该算法中的矫正参数, 并计算后验的地震震级, 即矫正震级.我们将该算法实际应用于西昌流动地震台网(XC)与中国地震台网(CN)的震级融合问题中.基于矫正震级与原始测定震级的对比研究表明, 矫正震级与固定地震台网原始测定震级之间存在一定偏离度的线性对应分布, 而西昌流动地震台网测定震级相比矫正震级整体偏小.本文所提出的多台网震级融合的贝叶斯算法为流动台网测定的不精确震级提供了一种震级矫正的快速算法, 考虑固定台网与流动台网测定震级的一致性, 固定台网测定震级的稳定性和准确性也得到同步提高.

     

天津遥测地震台网MD震级偏差分析

本文介绍了天津遥测地震台网M_D震级测定方法和测定精度,根据1987—1989年震级测定资料统计分析了本台网M_D相对于北京台网、河北台网和分析预报中心全国地震月报目录M_L震级的偏差,同时对本台网M_D和M_L测定震级偏差进行了比较,并对结果作了初步讨论和分析。     

首都圈数字遥测地震台网单台震级偏差研究

使用河北省数字遥测地震台网中心产出的观测报告,选取2002年1月～2003年7月的所有地震事件,将首都圈范围内的各台站记录到的数据检索整理,对样本数接近和超过100个的58个台站的数据进行了归类统计,计算了各台站单台震级与台网平均震级的偏差、平均偏差和标准离差,分析了产生震级偏差的原因,给出了台基校正值,校正后的震级偏差在±0.2之内的样本数达到了70%。结果显示,在震中距0～40km内,量规函数偏小。震级偏差主要来自于各台站的综合影响,进行台基校正是有意义的。     

影响福建数字遥测地震台网震级测定的部分因素

通过对福建数字遥测台网1999年所监测到的“9.21”台湾南投大震群和“9.23”福州小震群中的一系列较大地震进行分析，利用地震的时间和空间相对集中这一特点，有效地避开震源、路径及随时间变化的地质背景等因素对测定震级的干扰，发现了对测定台网平均震级影响的主要因素，不仅仅来自于台站地质背景的影响、台网使用的起算函数的影响，而且还发现在一定距离内地震周期也会对台网平均震级测定产生明显的影响。通过计算地动位移随震中距衰减的系数和起算函数随震中距增幅的系数，求出起算函数引起震级偏差的大小，提出了改进和消除这些影响的方法。     

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.     

Earthquake Engineering and Engineering Vibration Aims And Scope

正This journal is established by the Institute of Engineering Mechanics(IEM),China Earthquake Administration,to promote scientific exchange between Chinese and foreign scientists and engineers so as to improve the theory and practice of earthquake hazards mitigation,preparedness,and recovery.To accomplish this purpose,the journal aims to attract a balanced number of papers between Chinese and     

Foreword

Destructive earthquakes have caused great damage in China and the United States and collapsing buildings havecaused many deaths and injuries. The field of earthquake engineering studies earthquake hazards, the occurrence ofearthquakes of various magnitudes, the nature of the ground shaking during an earthquake, the vibration of structuresduring earthquakes, the strengthening of existing structures and the design of new structures to be earthquake resistant,and finally, how to cope with earthquake damage and restore a city to normal functioning. Such efforts are in progressin both countries, but unfortunately, the language barrier interferes with the free flow of information between China andthe Untied States. It would be mutually beneficial if some means could be developed to promote the exchangeof information across the Pacific Ocean. This new journal has been established for this purpose and its success willbe an important step in promoting earthquake engineering in China and the United States.     

WORLD ASSOCIATION FOR SEDIMENTATION AND EROSION RESEARCH(WASER)

正President:Giampaolo Di Silvio,Italy Vice Presidents:Ulrich C.E.Zanke,Germany Zhao-yin Wang,China The World Association for Sedimentation and Erosion Research(WASER),inaugurated on Oct.19,2004,is an independent non-governmental,non-profit organization.The mission of WASER is to promote international co-operation on the study     

Enhancing remote sensing research on global change to improve our understanding on Earth system processes

正Global Change includes climate change and other environmental changes caused by the joint interaction among various layers of Earth. From the positive side, global change provides new opportunities to human and other living forms on Earth. In the meantime, it creates tremendous challenges and negative impact. At present, the negative impacts have reached all primary processes of the global ecosystem and every aspect of human society, especially causing degradation of the ecosystem. For instance, intensive deforestation causes decline of biodiversity; global warming causes sea level rise and increases     

Solute concentrations in the lower niger river and the source rock contribution

Water quality analyses for the Niger River for the 1980/81 hydrological year are presented. The samples were collected from the main river at Lokoja, and from two main tributaries, the Kaduna and the Benue Rivers. Different water types were distinguished by the concentrations of major ions. The type Ca > Na > Mg > K - HCO₃ > SO₄ > Cl was represented at all stations during at least part of the year. Chloride was found to dominate the sulphate ion in the Kaduna and Niger, while the Benue maintained a higher concentration of sulphate relative to chloride all year round. Distinct patterns of seasonal variation in the ion concentrations were observed, particularly for the samples collected at Lokoja. Low ion concentrations were prominent during periods of high discharge, while low flow periods coincided with high dissolved ion concentrations. The contribution of rainwater to the total dissolved solids in the river waters was assessed indirectly using rainwater chemistry data from the Gulf of Guinea. The estimated rainwater contribution to the Lower Niger amounts to 5.15 mg 1^?1. Geochemical weathering calculations involving reactions of the four major minerals of granitic rocks - anorthite, biotite, albite, and K-feldspar - with carbon dioxide and water, can account for the average water composition of the Lower Niger. The proportion of the ionic components was also related to the occurrence of the respective element in the minerals.