A preliminary study of post-seismic effects of radon following the Ms 8.0 Wenchuan earthquake

The observation data for radon from national geochemical observation points have been collected and analyzed following the Ms 8.0 Wenchuan earthquake on 12th May, 2008 and a post-seismic effect of radon was observed. It has provided the most abundant record since the radon observation network had been set up in china. In this paper, the behaviour of the post-seismic effects of radon gas and water radon is reported. The results were obtained that observation points recording post-seismic effects of radon release were distributed mainly along the extended line of Longmenshan faults, and located on the boundary faults of regional tectonic blocks (Category II) and inside some tectonic blocks (Category II). The pattern of variation in radon emission observed was largely in the form of rising steps. A comparison was made with the variation of water level and flow observed simultaneously with radon measurement, to investigate a dynamic link with post-seismic radon with underground water conditions. This study confirmed a response of radon concentration to the seismic wave, and also raised other scientific issues, such as the dynamic association between geochemical composition of underground water and medium parameter variation of aquifers under dynamic loading, which may support the study of the mechanism of earthquake precursors of radon.     

Anomalous change of groundwater radon concentration monitored at Nakaizu well in 2011

An anomalous increase in radon concentration was measured at the Nakaizu observatory on the Izu Peninsula prior to the 2011 Tohoku earthquake using a custom-made radon counter. Since the increase was more than three times the standard deviation of radon concentration variations over 35 years of recorded data, it is considered likely that it is a precursor to the earthquake. Following the earthquake, the radon concentration decreased exponentially to the background level. The anomalous increase is explained using a modified volatilization model containing three important aquifer parameters: the groundwater saturation ratio, the fracture surface area per unit volume, and the porosity. The modified model can also explain the radon concentration behavior prior to the 1978 Izu-Oshima-Kinkai earthquake.     

Selectivity of seismic electric signal (SES) of the 2000 Izu earthquake swarm: a 3D FEM numerical simulation model

Although seismic electric signal (SES) has been used for short-term prediction of earthquakes, selectivity of SES still remains as one of the mysterious features. As a case study, we made a numerical simulation based on a 3D finite element method (FEM) on the selectivity of SES observed in the case of the 2000 Izu earthquake swarm. Our numerical results indicated that the existence of conductive channel under Niijima island could explain the reported SES selectivity.     

基于PI法的门源MS6.4地震前震中附近地震热点图像异常变化研究

基于1980年以来青海省和甘肃省区域地震台网的定位地震目录,分析了研究区最小完备震级,选取空间网格尺度为0.2°×0.2°、地震活动异常学习时间段和预测时间段均为3 a,应用图像信息（PI）法,分析了门源M_S6.4地震发生前震中附近地震热点图像的异常变化过程。结果表明,在2013年1月1日至2016年1月1日的预测时间窗内,冷龙岭断裂和祁连山北缘断裂附近存在明显的地震热点,且地震热点图像颜色偏深,发震概率较高,向前滑动至2014年1月1日至2017年1月1日,2015年1月1日至2018年1月1日和2016年1月1日至2019年1月1日3个预测时间窗,此两断裂附近仍存在地震热点,地震热点图像颜色逐渐由深变浅,而门源M_S6.4地震就落在PI法得到的地震热点内。门源M_S6.4地震前存在明显的地震热点,且地震热点相对集中,地震热点图像颜色由深变浅,震后消失;在祁连山北缘断裂附近,地震热点持续存在,分布较集中,地震热点图像颜色也呈由深变浅的过程。未来需关注祁连山北缘断裂,附近有发生强震的可能。     

双曲冷却塔塔筒水平地震响应分析

为明确冷却塔在水平地震下的内力环向分布特征及内在原因,同时探究不同地震波时程与规范反应谱所得内力差异的原因,以某大型双曲冷却塔为例,在动力特性分析的基础上,通过反应谱方法和时程方法的水平地震响应计算及对比分析,对上述两个问题进行了研究。研究表明:由于仅侧弯振型对水平地震有贡献,而塔筒的侧弯振型和实际响应均表现为整体侧倾并伴随微弱的截面“流动”变形,这也使塔筒各内力的环向分布分别呈现正弦、余弦分布特征;其整体侧倾可类比于悬臂杆结构,塔筒子午向轴力FY、子午向弯矩MY、剪力FXY和扭矩MXY的环向分布可借助悬臂杆侧倾时截面正应力和剪应力分布来解释;而截面“流动”变形则决定了环向轴力FX和环向弯矩MX的环向分布;整体侧移显著而截面变形极小也使FY和FXY的幅值在塔筒中下部明显大于FX;由于冷却塔第1阶侧弯振型在水平地震响应中往往起绝对主导作用,因此可先对所选地震波计算得到其反应谱,对比第1阶侧弯振型周期对应的水平地震影响系数α值,即可初步推断不同时程及规范反应谱方法所得结果的大小关系。     

Unusual Surface Latent Heat Flux Variations and Their Critical Dynamics Revealed before Strong Earthquakes

We focus on the possible thermal channel of the well-known Lithosphere–Atmosphere–Ionosphere Coupling (LAIC) mechanism to identify the behavior of thermal anomalies during and prior to strong seismic events. For this, we investigate the variation of Surface Latent Heat Flux (SLHF) as resulting from satellite observables. We demonstrate a spatio-temporal variation in the SLHF before and after a set of strong seismic events occurred in Kathmandu, Nepal, and Kumamoto, Japan, having magnitudes of 7.8, 7.3, and 7.0, respectively. Before the studied earthquake cases, significant enhancements in the SLHF were identified near the epicenters. Additionally, in order to check whether critical dynamics, as the signature of a complex phenomenon such as earthquake preparation, are reflected in the SLHF data, we performed a criticality analysis using the natural time analysis method. The approach to criticality was detected within one week before each mainshock.     

竖向不规则结构抗震性能研究现状及其在设计规范中的应用

结构竖向不规则布置是导致结构地震损伤破坏的主要原因之一.介绍了建筑结构沿竖向的强度、刚度和质量不规则布置的定义、不规则的主要内容及其在地震作用下损伤破坏的特点;总结回归了钢筋混凝土竖向不规则结构地震反应需求的研究现状以及国际上典型的结构设计规范中结构竖向不规则条款的限定.针对竖向不规则结构目前的研究现状,提出了今后值得进一步加强研究的方向.      

Anomalous Geomagnetic Signal Emphasized before the Mw8.2 Coastal Alaska Earthquake,Occurred on 29 July 2021

A very strong earthquake of magnitude Mw8.2 struck the coastal zone of Alaska (USA), on 29 July 2021. This earthquake was felt around the Gulf of Alaska, on a wide offshore area belonging to USA and Canada. In order to identify an anomalous geomagnetic signal before the onset of this earthquake, we retrospectively analyze the data collected on the interval 17 June–31 July 2021, via internet, at the two geomagnetic observatories, College (CMO)—Alaska and Newport (NEW)—USA, by using the polarization parameter (BPOL) and the strain effect related to geomagnetic signal identification. Thus, for both observation sites (CMO and NEW), the daily mean distribution of the BPOL and its standard deviation (STDEV) are carried out using an FFT band-pass filtering in the ULF range (0.001–0.0083 Hz). Further on, a statistical analysis based on a standardized random variable equation is applied to emphasize the following: (a) the anomalous signature related to Mw8.2 earthquake on the both time series BPOL*(CMO) and BPOL*(NEW); (b) the differentiation of the transient local anomalies associated with Mw8.2 earthquake from the internal and external parts of the geomagnetic field, taking the NEW observatory as reference. Finally, on the BPOL*(NEW-CMO) time series, carried out on the interval 7–31 July 2021, a very clear anomaly of maximum, greater than 1.2 STDEV, was detected on 22 July, with 7 days before the onset of the Mw8.2 earthquake.     

一个关于高柔结构顺风向抗风设计中考虑地震作用组合的概率模型及求解

基于概率方法建立了高柔结构顺风向抗风设计中,考虑地震作用组合的总水平荷载的计算模型并进行了求解．在基于Turkstra准则的具体组合分析中,考虑了风和地震作用作为离散随机过程的发生概率以及风速和地面加速度的概率分布特征,并按照随机变量及相应函数的概率密度关系,得到了风和地震作用的概率密度分布．后利用卷积方法,分析探讨了结构抗风设计中地震作用的组合,并给出了实际的高柔结构算例．该研究反映对于水平荷载由风荷载起控制作用的高柔结构,最大水平荷载验算中,考虑风和地震作用后组合的总荷载可能较抗震设计中考虑了风荷载组合的结果更为不利．     

预警的概念及相关物理问题

预警是现代社会减轻自然灾害的工作中最重要的物理概念之一,也是在预测/预报的物理问题没有得到解决的情况下最具实际意义的技术之一.文章介绍了与预警有关的概念和物理问题,包括预报和预警的概念,现地预警和异地预警,讨论了不同领域的预警技术中共同的物理问题,包括“有限传播”原理、“连锁效应”原理、“相似放大”原理,以及实际工作对预警系统的主要技术要求.