山西临汾中心地震台地电阻率EW测道曲线特征分析

将临汾中心地震台地电阻率EW测道电测深曲线,采用水平层状模型反演测区的电性结构,计算EW测道各层介质的影响系数,解释了地电阻率EW测道"夏高冬低"的年变现象。对地电阻率EW测向从2010年9月17日开始出现的趋势下降变化,采用褶积滤波法分析该区降雨和地下水位对地电阻率的影响,发现二者对地电阻率的影响都不显著。分析认为,当前存在的趋势异常变化是可信的,应密切跟踪此异常的发展变化。     

2020年7月12日唐山MS5.1地震前通州台井下地电阻率变化

通州地震台井下地电阻率观测于2019年11月完成建设,完成相关测试后于2020年投入实际观测。在2020年7月12日河北唐山M_S5.1地震前,地电阻率呈现出一定的变化,约从4月上旬开始NE和NW测道同步出现下降变化,6月中旬开始NW测道出现转折回升。EW测道同期存在一定的上升变化,但变化幅度约为NE测道幅度的1/4。此次地震的震源机制解为走滑型,最大主压应力方位为101°,与NE、NW和EW测道的夹角分别为70°、50°和10°。震前NE测道下降幅度最大,NW测道次之,EW测道变化幅度最小,符合实验结果和地震前地电阻率各向异性变化特征。     

平凉台井下地电阻率年变特征及相关性分析

本文简要介绍了平凉台井下观测系统,对平凉台井下地电阻率年变特征进行了分析,采用相关分析法对地电阻率与降雨量、地温的相关性进行了研究。结果表明:平凉台井下地电阻率测值具有明显的年变规律,表现为"夏低冬高"的形态,其中南北向测道的年变化较东西向测道更显著,高值多出现在3月,低值多出现在8月,且东西向测道有滞后的现象。地电阻率与降雨量的相关性较高,季节性降雨是导致其产生年变化的主要影响因素。地电阻率与浅层地温的相关性较好,而与深层地温的相关性较弱。     

四0四多极距地电阻率年变化特征分析

采用2018年6月—2020年6月间ZD8MI地电阻率多极距观测系统在四0四台的观测数据,分析各测道的年变化特征,发现随着观测极距的不同各测道年变特征也不同;通过不同极距实验观测和年变化模拟分析表明,浅层电阻率的变化相对较大,而深层的变化相对较小,四0四台的年变化是由浅层介质电阻率随温度的季节性变化引起的,不同测道的年变形态受浅层不同深度介质电阻率的变化出现相位差异。因此利用多极距观测系统进行不同深度范围的地电阻率观测,对定量识别表层非震干扰显得尤为重要。     

新沂地震台地电阻率反向年变分析

结合新沂地震台电测深曲线、 测区地质剖面资料, 建立了三维非均匀层状介质有限元模型. 以第一层介质电阻率变化模拟表层介质电阻率随季节性降雨的变化, 在模型中计算了3个测道的地电阻率年变化形态. 计算结果表明, EW和N45°E测道地电阻率随表层介质电阻率的增减同向增减, 而NS测道地电阻率则与表层介质电阻率变化相反. 该结果符合新沂台3个测道实际观测的年变形态．      

定西地电台地电阻率观测数据分析

受环境干扰影响,定西地电台于2014年迁址重建,新场地干扰小,观测系统稳定,产品数据连续可靠。选取2015—2021年该台地电阻率观测数据进行分析,可知：①NS、EW测道具有明显的夏高冬低型年变形态;②破年变低值异常：2017年,NS测道出现破年变异常、EW测道同时段出现测值波动,持续3个月后发生九寨沟M_S7.0地震(震中距260 km);2021年6—9月,NS、EW测道同步出现破年变异常,持续6个月后发生门源M_S6.9地震;③每年6—9月,受测区农田灌溉及降雨影响,NS、EW测道地电阻率测值波动明显。     

甘肃定西地电阻率年变形态及异常特征分析

通过数值模拟及褶积滤波方法,对甘肃省定西台地电阻率两测道“冬低夏高”的反向年变形态进行分析,并利用自适应计算变化幅度法提取该台地电阻率资料的中短期异常数据。结果表明,定西地电阻率的年变形态主要受地表薄层介质电阻率季节变化和降雨影响;褶积滤波法可以拟合短期降雨影响,并且可以过滤地电阻率的年变形态,但2021年出现的趋势性转折下降的低值破年变与降雨量和薄层季节干扰关系不大;九寨沟7.0级和门源6.9级地震前出现较为显著的中短期下降异常变化,最大下降率为0.983%;2022年门源6.9级地震后的两测道去年变趋势变化幅度中的异常形态依然存在,且并未恢复。因此定西台地电阻率对甘东南和祁连山中东段具有指示意义,有必要利用该方法进一步重点关注该区域的强震危险性。     

地电阻率变化成因分析 ——以宝昌台为例

中国地震台网地电观测以对称四极装置的地电阻率观测为主,其观测曲线通常存在长期变化、年变、日变和阶跃等,文中以宝昌台为例,通过反演、数值模拟等方法分析上述变化成因.宝昌台地电布极区地下的电阻率基本呈现水平分布,电测深曲线类型属于KH型.该台NS、EW测向的地电阻率自1993年至今一直存在长期下降变化,且变化速率存在显著的...     

河北昌黎地电阻率频谱特征分析

应用最大熵谱法分析昌黎地电阻率频谱成分特征,结果表明,地电阻率整点值存在明显日变特征,24 h全日波最强,半日波和1/3日波周期成分次之,主要受气温和固体潮影响。气温升高引起地电阻率下降,固体潮引起地下深层承压水位的日扰动变化,导致地电阻率变动。地电阻率日均值存在显著的"冬高夏低"准年变周期,与降雨量有关,利用褶积滤波法可以较好的去除降雨对地电阻率的影响。     

地埋钢缆对宝昌台地电阻率干扰的定量分析

宝昌台EW、NS测道地电阻率在2009年11月出现了显著的短时间下降变化,随后迅速恢复,EW测道自2010年2月底开始大幅下降,经现场落实认为这些变化与2009年11月中国移动公司在测区埋设的钢缆有关,2011年7月26日和27日经台站和中国移动公司协商后移除了部分钢缆,两测道的地电阻率观测值得到恢复.建立三维有限元模型计算了表层土壤处于非稳定冻结、稳定冻结和完全融通三个阶段钢缆对地电阻率观测的影响,计算得到:在稳定冻结阶段钢缆对观测的影响非常小,完全融通阶段的影响最大,非稳定冻结阶段的影响介于二者之间,且三个阶段计算得到的地电阻率变化值与观测值相吻合,从数值分析的角度确定了钢缆对宝昌台地电阻率观测的干扰.     

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     

SCIENCE CHINA Earth Sciences SUBJECT INDEX TO VOLUME 57(2014)

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