中国东部的尾波衰减经验关系和震级

从中国东部地区的ＤＤ－１短周期近震记录，取得尾波地动振动幅Ａ随尾波推移时间τ的衰减经验关系。     

泾阳台地震持续时间震级公式MD初探

用最小二乘法处理泾阳台ＤＤ－１地震仪记录资料，拟合适于泾阳台由地震波持续时间求算近震震级ＭＤ的公式：ＭＤ＝２．７ｌｇｒ—２．４（Δ≤１０ｋｍ），ＭＤ＝２．２９ｌｇｒ＋０．００１１８Δ－２．２５（１０ｋｍ＜Δ≤５２０ｋｍ），并对震级ＭＬ和ＭＤ进行误差分析。     

德令哈地震台震级偏差及台站校正值的研究

利用德令哈地震台DD—l记录到的746个近震，对其测定的震级偏差进行统计计算，发现DD—l测定的震级偏小。经过分析，指出了产生偏差的原因，并给出了校正值C= 0．15。     

湖北地方台站持续时间震级公式

本文利用这几年来湖北及邻区发生的300余次近震资料,分别计算了湖北区域地震台网和各台站的持续时间震级公式,初步讨论了这些公式的实用性。结果表明,区域台网范围内应用台网统一持续时间震级公式是可行的,个别台站由于环境条件和工作状态的明显差异,可适当进行台站校正。     

泾阳地震台近震震级（Ml）误差分析及其校正

本文对泾阳台1982—1989年457次单台近震震级同省台网近震震级对比进行统计分析,并对1990年1月—8月50次记录到的近震进行检验,得到泾阳台测定M_L震级精度为±0.205,经校正后的精度为±0.129,下降率为37.1％,尤其震中距小于100km的地方震,单台震级精度为±0.527,校正后震级精度为土0.156,下降率为70.4％。     

合肥遥测台风网限幅时间震级公式

为了满足遥测地震台网地震速报的需要，本文利用地震限幅时间拟合给出了合肥遥测台网确定限幅地震震级的经验公式，给出了精度分析结果，认为在近震范围内利用地震限幅时间确定遥测台网内外多台限幅情况下的地震震级，是一种可行的方法，与地震持续时间方法比较，具有速度快、精度高的优点。     

浙江台网MD震级公式的研究

本文利用浙江地震台网记录的近震资料,用多元回归分析法建立了单台和多台统一的持续时间震级公式,并对影响回归方程精度的因素作了分析讨论.文章认为,为了保证 M_D 的精度,必须考虑仪器放大倍数和震中距的影响.误差分析和检验结果表明,本文求得的 M_D 公式可以显著改进震级测量精度和系统偏差,适合浙江台站使用.     

合肥遥测台网限幅时间震级公式

为了满足遥测地震台网地震速报的需要，本文利用地震限幅时间拟合给出了合肥遥测台网确定限幅地震震级的经验公式，给出了精度分析结果，认为在近震范围内利用地震限幅时间确定遥测台网内外多台限幅情况下的地震震级，是一种可行的方法，与地震持续时间方法比较，具有速度快、精度高的优点     

汕头台网持续时间在测定震级中的应用

目前近震的震级测定大部分是采用里克特定义经改进后的公式:M_L=logA_μ+R(△)。但由于发震机制及各个地区的地质构造、岩石的介质特性等不同,致使地震波在传播过程中能量的吸收(衰减系数)也是各有差异的。汕头台网应用上式测定震级,R(△)采用地震观测规范提供的值,各个子台震级往往相差M_L=0.2-0.5,少数甚至相差0.8。长期以来,汕头基     

利用地震波持续时间测定近震震级的关系式

1.前言在地震波记录限幅的情况下,震级测定工作很难达到准确、稳定。这是一个普遍存在的问题。我们从实际工作中发现,在一定距离内地震波持续时间(F—P)与震中距△和地震波幅射的方向性关系不明显,而与震级大小有密切关系。震级大、持续时间长,反之则短。我们根据河南省台网的资料,研究了近震震级的M_L与地震波持续时间的关系,得出河南省台网13个测震台站的M_D公式。同时给出全省通用的水平向、垂直向M_D计算公式。     

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     

Calendar of events

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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.