2022年德令哈MS 6.0地震前地磁垂直强度极化异常特征分析

<正>1研究背景已有研究表明,岩石破裂时电磁波超低频段会出现信号异常,且临近破裂时岩石附近磁场强度会出现短周期前兆变化（郝锦绮等,2003）。地磁垂直强度极化方法是目前地震磁扰动定量分析中物理含义明确、分析过程完善且获取异常信息能力较强的方法之一（姚休义等,2018）。该方法基于频谱分析,通过地磁场垂直分量Z和水平分量（H或G）的频谱振幅相比来定义。数值模拟结果证明,一次源来自地壳内频率1 Hz附近的磁信号垂直分量幅值大于水平分量幅值,其比值大于1(Molchanov et al,1995),故可通过该比值来突出岩石圈异常信号,同时抑制外源场的电磁信号。     

研究地震和岩石破裂现象的非线性科学方法

本文以地震孕育和岩石破裂过程的阶段(包括裂纹系形成、变形局部化和断层形成、断层活动和松弛)为线索,阐述了非线性科学方法(包括分形几何学,自组织临界现象和混沌动力学)的应用,提出了地震孕育过程和岩石破裂各阶段的普适性特征、机理和要着重研究的课题.     

慢地震慢前兆的机制研究

通过岩石高温高压破裂实验与有机玻璃破裂试验的应力—应变曲线对比、地震波形记录(观测资料)与试样破裂波形(实验资料)对比、地震前后定点应变与主破裂前后应变形态变化的对比，认为慢地震是临界或亚临界破裂或预先滑动所致，是低频应变波动。它是材料屈服、弱化或塑性变化的必然结果。而慢前兆则是临近大地震(大破裂)前出现的诸如形变、低频地震波(破裂弹性波)等的短期及临震前兆现象，它比较可靠。但由于许多岩石主破裂前并无明显的临界破裂或预滑动现象，也并非所有岩石都一定出现明显屈服，所以也并非每个地震前都有慢地震，因此，也就不一定都出现低频波动。从而，也并不一定都出现相同的短期、临震前兆现象。     

岩石破裂以及破裂前信号的演变

地震是大量的岩石破裂事件.很多大地震之前都存在瞬态信号:电磁信号、磁场变化、电离层扰动、土壤导电率的变化以及其他震前信号.令监测人员奇怪的是,在震前短时间内一些震前信号会衰弱甚至消失不见.岩石中应力活化电流的发现提供了一个可能的解释,应力能够激活岩石中的移动电荷载体,即电子空位缺陷(electron vacancy d...     

真三轴压机刚度对岩石破裂声发射的影响及与地震活动性的联系.

本文叙述了岩石特征刚度与压机刚度比R对岩石破裂及声发射的影响.结果表明:当R>0.20时,岩样产生突发断裂;当R1.50时,断裂前没有平静期.缓裂时,声发射率的变化形式为(应力增至大于50％破裂应力后)平稳低(高)值——上升(下降)至极大(极小)值并持续之——破裂.      

岩石标本破裂时的电磁辐射和光发射

在做闪长岩和大理岩破裂试验时,同时记录到电磁辐射和光发射,并利用记录到的磁场值计算出了电场强度。结果表明,这个电场强度比压电效应形成的电场强度大2、3个量级,算出的破裂面之间的电压大于空气的击穿电压。因此,岩石破裂时裂缝间的空气被击穿,这就是发光的原因之一。 另外,发光的形状与岩石标本破裂的形状相似。本文提供了一种研究岩石破裂的新方法。     

倾斜扰动--一种可能的有效地震前兆

依据小地震时的倾斜记录和岩石破裂时的应变扰动记录提出，岩石破裂和微小地震可能引起倾斜扰动，这种扰动将可能是大地震的有效前兆。然而，如何区分干扰和前兆扰动还需仔细研究。     

不同性质岩块构成的样品破裂前的波速变化

用超声脉冲法研究了不同性质岩块构成的样品破裂前的波速变化。样品为长方形大理岩板,中心镶嵌大理岩、辉长岩、花岗岩,砂岩圆块。实验表明,样品破裂时裂纹穿过低强度镶嵌岩块而绕过高强度镶嵌岩块。在第一种场合样品破裂前,镶嵌岩块內波速变化显著,在第二种场合样品破裂前镶嵌岩块內波速变化不大。穿过两种岩石界面的波速测量表明,波速下降的起始点提前到样品破坏应力的60%左右。样品破裂前波速总的变化趋势是下降,但不是单调下降而呈现起伏。这说明介质不均匀性会对岩石破裂前的波速变化规律产生不可忽视的影响。      

汶川8.0级地震前后全国倾斜场变化初步分析

由于岩石介质的不均匀型,在易破区域会出现应力积累,伴随着倾斜会出现较大的变化。由岩石破裂实验可以看出破裂区在破裂前出现了体积变大（鼓包）或变小（凹坑）现象,如果在岩石表面放置倾斜仪器,我们不难得出各仪器的倾斜方向指向或背向破裂点。本文采用全国前兆台网地倾斜（水管）数据,使用5次曲面函数区域插值的方法,拟合出地倾斜场（图1）。     

汶川8．O级地震前后全国倾斜场变化初步分析

由于岩石介质的不均匀型,在易破区域会出现应力积累,伴随着倾斜会出现较大的变化。由岩石破裂实验可以看出破裂区在破裂前出现了体积变大（鼓包）或变小（凹坑）现象,如果在岩石表面放置倾斜仪器,我们不难得出各仪器的倾斜方向指向或背向破裂点。本文采用全国前兆台网地倾斜（水管）数据,使用5次曲面函数区域插值的方法,拟合出地倾斜场（图1）。     

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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