沉积物的地震及古地震效应*

古地震是依据地层中保留的沉积物变形记录而确定的。系统归纳总结地震诱发沉积物变形将为古地震研究提供理论基础,也有助于野外调查辨认这些记录。作者提出了一个初步的、供讨论与补充修正的地震触发沉积物变形分类的方案。变形的成因机制是分类的基础。这些特殊沉积物变形主要与地震有关,但其中一些变形往往也受其他多种因素的影响,因此要确定地震成因变形必须详尽研究相关的区域地质背景构造。     

量子地震模型:对汶川地震的解释

从大量的地震参数分析可知,在由同一主震引发的所有的余震发生的位置都不同。在发生地震之前,地震的震中位置都是一些相互独立、互不连续且发生了弹性应变的单元个体,笔者称这些独立不连续的弹性应变单元称为应变量子。综合前人研究成果,笔者建立了一个地震模型。运用该模型对2008年5月12日发生在中国汶川地震作了解释:由于在龙门山断裂带周围形成了许多的应变量子,这些应变量子的形成阻碍了龙门山断裂的运动,产生滑移亏损,从而造成在地震前测量到的龙门山断裂带速度场变化很不显著。2008年5月12日14时28分时,在龙门山断裂周围已形成应变量子中的其中一应变量子最先达到它的最大储能,释放它所储存的应变能,引发了汶川Ms8.0地震。此次地震产生的地震波引发了龙门山断裂周围地壳应力的重分布,使得其他应变量子提前达到最大储能,释放出能量,于是触发成千上万次余震。此外,我们或许可以通过观测断裂滑移速率的变化情况来预测断裂周围应变量子的形成,从而来预测该断裂是否存在潜在地震的可能。     

The effects of a large destructive local earthquake on earthquake preparedness as assessed by an earthquake preparedness scale

A multi-act scale for measuring the earthquake preparedness of individuals and small businesses was developed and used to assess the earthquake preparedness and the perceived difficulty of becoming prepared for earthquakes of 291 University of Southern California undergraduate students approximately 3 weeks prior to the 5.9 magnitude Whittier Narrows earthquake on 1 October 1987. These data were then compared with similar information collected over a 2 1/2 month period following the earthquake from randomly selected samples of subjects that had participated in the original survey. In one case, levels of preparedness of a single group were measured at approximately 2 week intervals (the repeated measures study). In a second case, this information was collected at different points in time following the earthquake from different groups of subjects (the between groups study). Results indicated an initial increase in earthquake preparedness which was significant for subjects in the repeated measures group and which approached significance for subjects in the between groups. This increase in preparedness was maintained for subjects in the repeated measure study but gradually declined to pre-earthquake levels for subjects in the between subjects study. Subjects in the repeated measures study also perceived earthquake preparedness as a significantly less difficult task following the earthquake. Level of perceived difficulty continued to decline over the 2 1/2 month study period. Declines in perceived difficulty for the between subjects study were more erratic, and were only approximately 1/3 of that for the repeated measures group at the end of 2 1/2 months.     

The foreshock sequence of haicheng earthquake and earthquake swarm—the use of foreshock sequences in earthquake prediction

We have compared the Haicheng foreshock sequence with several earthquake swarms which occurred in its neighborhood. The spatial distribution of the earthquakes is relatively concentrated. For the most part, the events occurred within a few kilometers of each other. The focal mechanisms are comparatively stable. However, there are several swarms in which the variations of focal mechanisms are quite obvious after the occurrence of the largest event of the sequence, which would allow it to be recognized as a swarm. However, there are also swarms whose focal mechanisms are no less stable throughout the sequence compared to the Haicheng foreshock sequence. This feature could thus not be used to identify a foreshock sequence. The temporal distributions of foreshocks and swarms are quite similar in some cases. This is again not a definite criterion for identifying foreshocks, but is worthy of further study. Thus, no definite criterion for identifying foreshock sequences has been found. However, some earthquake swarms may be recognized in their later stage.Finally, we introduced a magnitude sequence with gaps which can be used to see whether a large event is still forthcoming. This method (in conjunction with other methods) could be used in areas prone to large earthquakes, immediately before a large event, to improve the probability of predicting the occurrence of a large event. We also report that the temporal distribution of all the sequences showed a 12-hour recurrence pattern that corresponded with the earth tides, indicating that tidal forces might be influencing foreshocks and earthquake swarm occurrence.     

芦山地震发震构造及其与汶川地震关系讨论

芦山地震发生在巴彦喀拉块体与华南块体之间龙门山推覆构造带南段。野外考察表明,芦山地震在震中区没有形成具有构造地质意义的地震地表破裂带,仅在各山前陡坡地带出现平行于山麓陡坡的张性地裂缝、山地基岩崩塌、滑坡等边坡震动失稳现象和震动引起的砂土液化现象。重新定位的芦山地震余震分布、震源机制解和地表构造地质等分析表明,芦山地震的发震断层为一条现今尚未出露地表、其上断点仍埋藏在地下9 km以下地壳中的一条盲逆断层,走向212°,倾向NW,倾角38°±2°,上断点以上至地表的构造变形符合断层扩展背斜模型。根据汶川地震和芦山地震的余震空间分布、地震破裂过程、深浅构造关系等差异反映出它们是分别发生在龙门山推覆构造带中段和南段的两次独立地震破裂事件。     

地震断层的渗透性

剪切带的流体压力因关系着地震断层的滑动强度以及应力释放过程一直备受重视。断层带的渗透率结构对认识断层带内流体活动状况、断层强度、摩擦稳定性以及同震过程等至关重要。文中介绍了断层带渗透率研究的原理、方法,总结了国内外最新的研究成果。脆性域断层的渗透率表现为核部低、两侧高的典型结构,断层泥通常具有最低的渗透率和强各向异性。在地震周期中,断层带的渗透性表现为突然增强-逐渐降低的过程。胶结、水岩反应及溶解-沉淀是间震期断层愈合的主要方式。热压作用是一种有效的断层弱化机制。当断层泥的渗透率小于10-18 m2量级时,地震会伴随强烈的同震热压效应。     

Commensurability of earthquake occurrence

During recent years huge earthquakes frequently occurred and caused surprise attack on many places of the globe. Frequent exceptional strong disasters of earthquakes remind that we must strengthen our research on cause of formation, mechanism, prediction and forecast of earthquakes, and achieve the goal of advancing the development of Earth science and mitigation of seismic disasters. The commensurability of earthquake occurrences has been studied by means of the commensurability revealed by the Titius–Bode law in the paper. The studied results show that the earthquakes basically all occur at the commensurable point of its time axis, respectively. It also shows that occurrence of the earthquakes is not accidental, showing certain patterns and inevitability, and the commensurable value is different for earthquakes occurring in different areas.     

Local earthquake quantification

The diversity of noise conditions, and, consequently, the diversity of types of seismographs that are found in different environments, make it unlikely that a single method of determining magnitudes for local earthquakes will be developed. In each area local studies must be carried out to determine the appropriate attenuation-distance function, taking into account known structural features. Each locally determined magnitude scale should be related to either a standard teleseismic scale, or preferably, to Richter's original local magnitude scale, M_L.     

如何解决开展防震宣传担心引起谣传问题

解决开展防震宣传活动担心引起谣传问题 ,必须做到 :一、更新观念 ,与时俱进 ;二、端正认识 ,进一步理解自己的职能 ;三、把积极、大胆开展活动作为解决谣传问题的根本途径 ;四、注意工作方法 ,尽量避免群众“担心”。     

Tectonics and earthquake mechanism of the shallow earthquake seismic belt,the Himalaya

The foci distribution of upper mantle earthquakes occurred between 1961 and 1972 in Himalayan, Tibetan and Hindukush regions, were studied and compared. The V-shaped pockets above a vertical plane have shown a relationship with the dip-slip type or normal faulting at the borders of the continental plates. The left-lateral and right-lateral displacements of Kirthar-Sulaiman shear zone and Brailly fault respectively found by the focal mechanism indicate a relative difference in motion between the Kashmir region and Nepal region and the uniform and right angle displacement of Tibetan Plateau has produced the Saradah depression. On the basis of seismic and geological evidences a simple tectonic model is proposed.     

Investigation of insured earthquake damage

The assessment of the loss potential caused by natural perils is a very important task for all insurance companies working in hazard-prone markets. It has to be based on two crucial items: the frequency of events and the investigation of their effects on the insured portfolio. This article deals with the second aspect, i.e. an evaluation of the insured damage caused by two earthquakes, namely those occurring near Albstadt, Germany, on 3 September 1978, and in central Chile on 3 March 1985. The results of the analysis of the earthquake in central Chile enable the mean damage ratio (damage in relation to the value) to be related to the height and the type of construction of the buildings affected. The Albstadt earthquake data permit an illustration of the effects of the type of subsoil on the mean damage ratio. The damage to individual buildings can be described by a lognormal distribution. Possible applications of these results are mentioned.     

Investigation of insured earthquake damage

The assessment of the loss potential caused by natural perils is a very important task for all insurance companies working in hazard-prone markets. It has to be based on two crucial items: the frequency of events and the investigation of their effects on the insured portfolio.This article deals with the second aspect, i.e. an evaluation of the insured damage caused by two earthquakes, namely those occurring near Albstadt, Germany, on 3 September 1978, and in central Chile on 3 March 1985. The results of the analysis of the earthquake in central Chile enable the mean damage ratio (damage in relation to the value) to be related to the height and the type of construction of the buildings affected. The Albstadt earthquake data permit an illustration of the effects of the type of subsoil on the mean damage ratio. The damage to individual buildings can be described by a lognormal distribution. Possible applications of these results are mentioned.     

水库诱发地震评价研究

本文是在总结了水库地震的基本情况和主要特征后,以工程地质学理论为基础,并结合地震地质学,对水库地震进行了评价.其目的是为了确保大坝施工期与建成后的安全运行,并根据库坝区的诱震地质条件,正确评价诱发地震的可能性及其可能造成的危害,为工程建设采取合理的对策提供依据.其步骤分为3步:水库地震可能性评价、水库地震危险性评价与水库地震监测和预测研究.其内容为区域工程地质、构造地质、水文地质、地震与水库地震监测,并依据世界水库地震资料的对比分析,总结出:构造断裂型、地表卸荷型与岩溶塌陷型3种主要水库地震类型的判据.其评价方法,主要是对水库地震综合性分区评价及水库地震强度的评价方法进行了详细的论述,具有较高的实用价值.     

水库诱发地震评价研究

本文是在总结了水库地震的基本情况和主要特征后,以工程地质学理论为基础,并结合地震地质学,对水库地震进行了评价。其目的是为了确保大坝施工期与建成后的安全运行,并根据库坝区的诱震地质条件,正确评价诱发地震的可能性及其可能造成的危害,为工程建设采取合理的对策提供依据。其步骤分为三步：水库地震可能性评价、水库地震危险性评价与水库地震监测和预测研究。其内容为区域工程地质、构造地质、水文地质、地震与水库地震监测,并依据世界水库地震资料的对比分析,总结出：构造断裂型、地表卸荷型与岩溶塌陷型3种主要水库地震类型的判据。其评价方法,主要是对水库地震综合性分区评价及水库地震强度的评价方法进行了详细的论述,具有较高的实用价值。     

Toward petascale earthquake simulations

Earthquakes are among the most complex terrestrial phenomena, and modeling of earthquake dynamics is one of the most challenging computational problems in science. Computational capabilities have advanced to a state where we can perform wavefield simulations for realistic three-dimensional earth models, and gain more insights into the earthquakes that threaten California and many areas of the world. The Southern California Earthquake Center initiated a major earthquake research program called TeraShake to perform physics-based numerical simulations of earthquake processes for large geographical regions, at high resolution, and for high frequencies. For a large scale simulation such as TeraShake, optimization problems tend to emerge that are not significant in smaller scale simulations. This involves both large parallel computation and also massive data management and visualization coordination. In this paper, we describe how we performed single-processor optimization of the TeraShake AWM application, optimization of the I/O handling, and optimization of initialization. We also look at the challenges presented by run-time data archive management and visualization. The improvements made to the TeraShake AWM code enabled execution on the 40k IBM Blue Gene processors and have created a community code that can be used by seismologists to perform petascale earthquake simulations.     

A Mediterranean earthquake project

Cumulative frequency and cumulative energy may vary from one sample of earthquakes to another either in the same or in the opposite sense. Conditions for the variations are deduced theoretically and illustrated by numerical examples.     

Foreshocks and earthquake prediction

Results of a statistical investigation of the magnitude and time distributions of foreshocks in the area of Greece are reported. Further evidence is presented that the parameter b, in the frequency—magnitude relation, has a smaller value before than after the main shock, and that the time distribution of foreshocks follows a statistical law similar to that followed by aftershocks. The difference in magnitude between the main shock and the largest foreshock seems to be independent of the magnitude of the main shock. The average of this difference has been found equal to about two magnitude units. The significance of these results to the problem of statistical prediction of earthquakes is noted.     

Hypotheses for earthquake occurrences

Very little work has been done in generating alternatives to the Poisson process model. The work reported here deals with alternatives to the Poisson process model for the earthquakes and checks them using empirical data and the statistical hypothesis testing apparatus. The strategy used here for generating hypotheses is to compound the Poisson process. The parameter of the Poisson process is replaced by a random variable having prescribed density function. The density functions used are gamma, chi and extended (gamma/chi). The original distribution is then averaged out with respect to these density functions. For the compound Poisson processes the waiting time distributions for the future events are derived. As the parameters for the various statistical models for earthquake occurrences are not known, the problem is basically of composite hypothesis testing. One way of designing a test is to estimate these parameters and use them as true values. Momentmatching is used here to estimate the parameters. The results of hypothesis testing using data from Hindukush and North East India are presented.     

阪神地震中大开地铁车站震害机制数值仿真分析

1995年阪神地震中,神户市的地下结构遭受了严重的破坏,尤其是地铁车站的破坏最为严重,其中大开地铁车站有一半以上的中柱发生坍塌,导致地面坍塌近2.5 m。对大开地铁车站的震害进行了全面地描述,基于大型商用有限元软件ABAQUS,采用在该软件上二次开发的土体非线性黏弹性动力本构模型模拟土在循环荷载作用下的动力特性,采用黏塑性动力损伤模型模拟混凝土在循环荷载作用下的拉、压应力-应变关系,对大开地铁车站的非线性地震反应进行了数值仿真分析,给出了破坏演化过程,把有限元分析的结果与大开地铁站的实际震害现象进行了对比,结果表明：数值仿真分析结果能够合理地解释大开地铁车站的主要震害现象,建模方法能够被用来进行地下结构的非线性地震反应分析。     

Perception of earthquake risk: a study of the earthquake insurance pilot area in China

In 2014, China will pilot its first earthquake insurance program, and the inhabitants’ perception of earthquake risk in the pilot area is significant for the implementation of this plan. In this study, the authors conducted a field survey in four districts in the insurance pilot area to investigate the factors affecting the earthquakes risk perception of residents. The survey concentrates on the factors of hazard experience and residents’ house type and shows that people who have experienced more earthquakes tend to have a lower risk perception while people who have suffered serious earthquake loss tend to have a higher risk perception. For the house type factor, the author finds that house type is correlated with the risk perception from an earthquake. The effect on risk perception is significantly reduced when people enhance their house type with brick walls, concrete beams, and column. Furthermore, gender, income, and education level also have direct effects on how residents perceive of the risk from an earthquake.