2008年盈江地震序列的震源参数和震源机制相关系数研究

基于云南数字地震台网记录的2008年盈江地震序列的数字波形资料,采用波谱分析方法和Brune震源模型,得到盈江地震序列的震源参数。利用两次地震事件的相同台站的震源谱参数（零频振幅）计算谱振幅相关系数,据此对地震的震源机制进行聚类分组,并收集和对比地震序列已知的震源机制解结果,发现每组内震源机制解P轴的相关性较好,且相关系数越大,P轴的方位角就越接近。将盈江地区划分为三个研究区,联合震源参数的应力降和聚类分组中每组的平均震源机制解结果研究地震序列发生过程中应力的释放水平和应力场方向变化特征。结果表明：不同阶段震源机制解类型的变化和转化特征一定程度上反映了孕震过程中区域应力场随时间的变化特征,并且地震震源机制解类型在时间段上的集中并向区域构造应力场方向转换的现象可能是发生强震的标志。震源机制解分组类型和对应类型的地震的应力降有一定依赖关系,震源机制解类型反映的应力场与区域应力场接近的地震应力降高,震源机制解类型反映的应力场与区域应力场差距较大的地震应力降普遍较低。     

2008年盈江地震序列的震源参数和震源机制相关系数研究

基于云南数字地震台网记录的2008年盈江地震序列的数字波形资料, 采用波谱分析方法和Brune震源模型, 得到盈江地震序列的震源参数。 利用两次地震事件的相同台站的震源谱参数(零频振幅)计算谱振幅相关系数, 据此对地震的震源机制进行聚类分组, 并收集和对比地震序列已知的震源机制解结果, 发现每组内震源机制解P轴的相关性较好, 且相关系数越大, P轴的方位角就越接近。 将盈江地区划分为三个研究区, 联合震源参数的应力降和聚类分组中每组的平均震源机制解结果研究地震序列发生过程中应力的释放水平和应力场方向变化特征。 结果表明: 不同阶段震源机制解类型的变化和转化特征一定程度上反映了孕震过程中区域应力场随时间的变化特征, 并且地震震源机制解类型在时间段上的集中并向区域构造应力场方向转换的现象可能是发生强震的标志。 震源机制解分组类型和对应类型的地震的应力降有一定依赖关系, 震源机制解类型反映的应力场与区域应力场接近的地震应力降高, 震源机制解类型反映的应力场与区域应力场差距较大的地震应力降普遍较低。     

腾冲火山区地震构造应力场研究

通过对腾冲火山区强震和中小地震震源机制制解分析,对火山区构造应力场方向空间分布,以及震源类型和破裂特征作了研究。利用腾冲火山区中小地震地震波资料,计算得到的地震震源处剪应力强度值,对火山区应力场强度或初始应力状态进行了研究。腾冲火山区构造庆力场主要为北北东－北东－北东东向,接近水平的压应力场。腾冲火山区凛环境剪应力场高值区所包围的低剪应力值分布区。腾冲火山区地震震源具有多种类型,震源破裂具有多种形     

邢台地震序列的应力释放调整过程

利用邢台地震序列震源机制解反演邢台老震区分时段应力场,并对震源机制和应力场结果进行分析。研究结果显示:邢台老震区的震源错动类型以走滑类型为主,遍布整个震源区;序列整体和3个时段的应力场反演结果基本一致,且与华北地区其他强震的应力方向相同,表明邢台地震的发生受华北区域构造应力场控制;应力场反演得到的邢台地震序列现今的摩擦系数显示处于拜尔利摩擦系数的范围,区域应力方向有利于断层活动,而地震活动频度和强度偏低,推断目前震源区处于某种平衡状态,需要进一步研究震源区深浅应力状态的耦合关系。     

大震前显示的地震震源机制趋于一致的变化

在构造应力场的制约下强震孕育过程中特定阶段, 震源区中小地震震源机制与构造应力场的方向大体一致, 根据这一特点, 定义各个震源机制解的P轴, B轴, T轴和构造应力场的3个应力主轴在3维空间的夹角之和为一致性参数a, 研究强震前应力场变化特征。 对2006年11月15日千岛岛弧M_W8.3地震和2001年6月23日秘鲁M_W8.4地震研究表明, 大震发生前孕震区一致性参数a比较低, 震源机制与构造应力场的差异较小, 说明这些前震受到了震源区应力场的统一作用, 而主震发生之后震源机制解的一致性参数比较高, 说明后续发生的地震的震源机制散乱, 表明背景应力场的控制作用开始减弱。     

永善—大关7.1级地震序列震源区应力场分析

由云南永善－大关Ｍｓ７．１级地震序列中的１１个Ｍｓ≥４级震的震源机制解和９８个小震震源机制解，分析了震源区应力场的基本图象和变化形态。结果表明，震源区应力场的基本图象和构造应力场的方向相符。Ｍｓ７．１级主震未对震源区应力场的方向产生可觉察的改变。大量小震机制解的空间向的优势方向与主震机制解一致。     

由地震释放的地震矩叠加推导平均应力场

文中给出了根据地震释放的总地震矩求解平均应力场的方法,并使用加入随机误差的人工合成震源机制解数据和唐山余震区震源机制解数据对其进行检验。由检验结果可知,该方法可以应用于区域平均应力场的求解。使用的震源机制解资料越多,所得结果越稳定,且更接近真实的区域应力场。该方法的优点是: 用每个地震的震级作为权重,能够较好地反映出大小地震在应力场反演中的不同贡献; 并且在计算过程中不需要知道震源机制解2个节面中哪个节面为地震断层面。     

基于汶川地震序列震源机制解对龙门山地区构造变形模式的初步探讨

本文采用理论震源机制解的分析方法,以汶川地震序列震源机制解为约束,探讨龙门山地区构造变形模式及其与汶川地震序列的关系.通过有限元模拟,计算了龙门山地区不同构造变形模式下的构造应力场,得到了理论震源机制解,并与汶川地震序列实际震源机制解进行对比分析,初步探讨了该区构造变形模式对汶川地震序列的影响.结果显示,在龙门山地区,青藏高原内深部构造变形快于地表的构造变形模式下,区域构造应力场对应的理论震源机制解与汶川地震序列震源机制解的相符程度较高.这种一致性可能表明:(1)青藏高原内部深部构造变形快于地表,是龙门山地区比较合理的构造模式;(2)构造应力场是影响汶川地震序列震源机制的重要力学因素.     

中国及周边地区2000-2004年构造应力图

地震震源机制解是分析岩石圈现代构造应力场的基本资料,直接反映了地壳断层结构的活动特征.因此,整理统计并不断更新地震震源机制解资料及其反映的现今构造应力场状况,并进行构造分析是非常基础且重要的工作.     

云南及邻区地壳应力场研究

地壳应力场对探讨区域构造动力过程和形变机制有重要意义.为了获得云南及邻区精确的构造应力场以及确定先前研究中存在差异地区的构造应力场,本研究首先在搜集研究区已有震源机制解的基础上,使用gCAP方法反演了近年来发生的地震震源机制解,共获得研究区震源机制解1302个;其次,在应力场反演时,提出了定量设置反演网格大小的方法,并删除阻尼和无阻尼反演应力场结果性质存在差异的网格.最终,基于大量震源机制解资料获得研究区精确的应力场：(1)云南及邻区震源机制解类型以走滑型为主,遍布整个研究区,逆走滑和逆冲型地震集中分布在云南与四川盆地交界地区,正断型和正走滑型地震较少,主要分布在滇西和滇西北地区;研究区震源机制解的多样性,在一定程度上反映了研究区构造活动和应力场的空间差异性.(2)云南及邻区整体应力场表现为：主压应力轴方位迹线呈以西北角为中心的扇形分布,主张应力轴方位迹线呈以西北角为中心的弧形分布,总体上反映青藏高原物质向东南的运移作用对研究区应力场具有控制作用.(3)研究区应力场类型以走滑型为主,局部地区出现逆冲和拉张型应力场,所得结果与前人应力场研究结果总体上一致.(4)腾冲火山区地壳应力场为走滑...     

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.