The seismic future of cities

The final projected doubling in Earth’s population in the next half century, requires an additional 1 billion housing units, more dwellings constructed in a single generation than at any time in Earth’s history. Earth’s tenfold increase in population has occurred during a time that is short compared to the return time of damaging earthquakes. In the next century, therefore, earthquakes that had little impact on villages and towns, will be shaking urban agglomerations housing upwards of 12 million people. An epicentral hit on a megacity has the potential to cause 1 million fatalities. The incorporation of earthquake resistant structures in the current global building boom, despite successes in the developed nations, has been neglected in the developing nations where historically earthquake damage has been high. The reasons for this neglect are attributed to indifference, ignorance and corrupt practices, not due to an absence of engineering competence. Never has a generation of earthquake engineers been faced with such a grave responsibility to exercise their skills, both political and technical, as now.

The eye is bewildered by “a city become an heap”. Robert Mallet (1862).

     

The possible changes of tectonic stress fields in North China in 16–17th centuries

The ancient tectonic stress field in North China during 16–17th centuries were recovered by studying seismogenic faults of four great earthquakes. Three of them are dip slip events, the direction of the maximum principal stress is vertical, and that of the minimum principal stress is in the NW—SE direction and nearly horizontal tensile stress. Another earthquake is a complicated one which includes thrust and dip-slip activities. The above-stated character is quite different from that of present stress field, it is inferred that the stress field has significantly changed since 16th century, the main stress axis revolved an angle of 90 degrees nearly. The mantle upheaval in the faulted basins in North China during 16–17th centuries may cause the tensile stress field and a series of great earthquakes. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 144–148, 1992.     

20世纪的十大灾难性地震(待续)

叙述了 2 0世纪全球 10次灾难性地震发生的时间、震级、地点、伤亡人数、建筑物遭破坏以及救灾的情况 ,记述了一些地震的前兆现象和经济损失。     

The Skeptical Environmentalist: A Sociocultural Perspective

Bjorn Lomborg's critique of environmentalism has been praised by The Economist as ‘right’ on its main points and ‘just’ in its criticism of much green activism, and damned by Scientific American as a ‘failure’ in its purpose of describing the state of the world. Most of the debate has centred on Lomborg's treatment of environmental issues. But the book is about more than the environment, and its flaws extend beyond his use and interpretation of the data. This revised version was published online in July 2006 with corrections to the Cover Date.     

20世纪十大灾难性地震(续完)

叙述了２０世纪全球１０次灾难性地震发生的时间、震级、地点、伤亡人数、建筑物遭破坏以及救灾的情况,记述了一些地震的前兆现象和经济损失。     

地震灾情因社会发展而加重--20世纪全球地震灾害综述

２０世纪中国是世界上地震灾害最严重的国家。地震造成的经济损失最严重的是日本,美国,中国居第二,三位。全世界地震灾情有逐世纪加重的趋势。地震减灾研究有两点进展;１．中国有一次成功的临震预报;２．日本抗震建筑有效。全世界的未来地震灾情形势依然严峻。     

An Atlas of ShakeMaps and population exposure catalog for earthquake loss modeling

We present an Atlas of ShakeMaps and a catalog of human population exposures to moderate-to-strong ground shaking (EXPO-CAT) for recent historical earthquakes (1973–2007). The common purpose of the Atlas and exposure catalog is to calibrate earthquake loss models to be used in the US Geological Survey’s Prompt Assessment of Global Earthquakes for Response (PAGER). The full ShakeMap Atlas currently comprises over 5,600 earthquakes from January 1973 through December 2007, with almost 500 of these maps constrained—to varying degrees—by instrumental ground motions, macroseismic intensity data, community internet intensity observations, and published earthquake rupture models. The catalog of human exposures is derived using current PAGER methodologies. Exposure to discrete levels of shaking intensity is obtained by correlating Atlas ShakeMaps with a global population database. Combining this population exposure dataset with historical earthquake loss data, such as PAGER-CAT, provides a useful resource for calibrating loss methodologies against a systematically-derived set of ShakeMap hazard outputs. We illustrate two example uses for EXPO-CAT; (1) simple objective ranking of country vulnerability to earthquakes, and; (2) the influence of time-of-day on earthquake mortality. In general, we observe that countries in similar geographic regions with similar construction practices tend to cluster spatially in terms of relative vulnerability. We also find little quantitative evidence to suggest that time-of-day is a significant factor in earthquake mortality. Moreover, earthquake mortality appears to be more systematically linked to the population exposed to severe ground shaking (Modified Mercalli Intensity VIII+). Finally, equipped with the full Atlas of ShakeMaps, we merge each of these maps and find the maximum estimated peak ground acceleration at any grid point in the world for the past 35 years. We subsequently compare this “composite ShakeMap” with existing global hazard models, calculating the spatial area of the existing hazard maps exceeded by the combined ShakeMap ground motions. In general, these analyses suggest that existing global, and regional, hazard maps tend to overestimate hazard. Both the Atlas of ShakeMaps and EXPO-CAT have many potential uses for examining earthquake risk and epidemiology. All of the datasets discussed herein are available for download on the PAGER Web page (). T. I. Allen and M. G. Hearne—contracted through Synergetics Incorporated.     

Earthquake migration in East Asia mainland (I)—The migration of huge earthquakes and volcanic activity from West Pacific Trench to the Chinese mainland

The researches in this paper disclose a huge earthquake migration series that lasted more than one century—from the 17th century to the early day of the 18th, transverse migration of huge earthquake from West Pacific trench to the Chinese mainland, lasted about 134 a, the distance is about 2600 km, the velocity is about 19 km/a, and the direction of migration agrees with the direction of plate subduction and vertical to the strike of plate boundary. The migration has two branches. One extends westwards and terminates at the central longitude belt (Helanshan—Liupanshan fault zone) of the Chinese mainland, triggered the strongest seismicity episode in North China, including 4 earthquakes withM ⩾8.0. The other extends northwards, passing through Korea Peninsula, terminates at the north part of Heilongjian Province, and triggered the volcanic eruption activity in Changbaishan and Wudalianchi. The time-space linearity of migration is good. Its velocity is stable and its activity attenuates gradually. It is estimated that it is related with the disturbance of asthenosphere matters caused by the sudden acceleration of the subduction of the trench plate. There are two similar transverse migration series from 1498 to 1556 and from 1843 to 1927, and the velocities are 36.2 and 33.7 km/a respectively.     

Dynamic variation of ambient shear stress field before and after three strong earthquakes in Yunnan

IntroductionThecrustaltectonicmovementisacomplicatedevolutionprocesswithtimeandspace.Spatially,themovementofcrustaltectoniciscloselyrelatedtotheinter-movementandinteractionofmulti-leveledcrustalblocksinacertainregionandtheirborderfaults.Temporally,themovementiscloselyrelatedtothatofmulti-leveledcrustalblocksandtimesequencedevelopmentofinteraction.Anearthquakeoccurrenceistheresultofsuddenruptureofcrustmediaundertheactionoftectonicstressfield,isalsoacomplicatedprocessinnercrust.Duetotheobviousi…     

Study on the relationship between geothermal exploitation and seismic activity in Xi’an region

Based on the analysis of the induced earthquakes in China and abroad, we get some ideas about earthquakes induced by pumping water out of a well or injecting water into a well. The induced earthquakes usually occur near the well, and they are generally small earthquakes. The earthquake sources are shallow, and they belong to the main shock-after shock type of earthquake or the swarm-type of earthquake. The magnitude and the quantity of the induced earthquakes obviously depend on the pressure and the quantity of water pumped or injected. These earthquakes happen as soon as pumping or injecting occurrence, or after ten or twenty days, they may occur at the time of injecting mud or injecting high pressure water when a well is being drilled, or at the time when the ground water is being normally exploited. A large quantity of hot water has been exploited since 1990 in Xi’an, and the quantity of water exploited has been increasing year by year, as a result the groundwater level has been dropping with the water pumped out and the water level is high in summer and low in winter. The earthquakes in Xi’an region belong to the solitary-type and they spread outside Xi’an city where the wells are concentrated but no earthquake happens. The seismic frequency and the energy released have no relation with the quantity of water exploitation or the water level in the well. It is considered that geothermal exploitation does not induce earthquakes in and around Xi’an because of its specially geological condition. Foundation item: Project sponsored by the Landslide Office of Shaanxi Province and Society of Disaster Reduction of Shaanxi Province.     

2007年世界灾害地震综述

2007年世界地震活动水平与往年比较是非常之高,但是地震灾情很轻,死亡总计392人,伤15000人,经济损失大约200亿美元。日本的灾情较重。     

Dynamics of interaction between fields of seismicity and surface deformations (Bishkek geodynamic test area)

The spatial-temporal dynamics of surface crustal movements revealed from GPS data is compared with seismicity in the Bishkek geodynamic test area documented in the regional KNET catalog. The geological information system (GIS) GeoTaim 2.0 is substantially improved, which allowed variations in seismicity and deformation fields to be analyzed in the 3D raster. It is shown that seismicity and surface deformations are correlative in the test area. The periods with extreme values of contraction and the extension rates of the Earth’s surface areas are accompanied by enhanced seismicity and strong earthquakes. The increase in the spatial gradient of surface crustal movements coincides with changes in the azimuths of compression axes indicated by mechanisms of earthquakes that occurred at depths of up to 25 km. For a better geological—geophysical interpretation of interactions between deformation and seismicity fields in the Bishkek geodynamic test area, the spatial system GPS stations and measurement frequency need substantial improvement.     

2021年全球地震灾害概要

利用多渠道收集到的地震灾害资料,对2021年全球地震活动及地震灾害进行了整理,绘制了21世纪前20年全球灾害地震频度与伤亡情况变化曲线及2021年灾害地震分布图,汇总了造成人员伤亡的地震信息及灾害情况,对重大地震灾害做了详细分析,并总结了2021年全球地震灾害的主要特征。与往年地震情况相比,2021年全球地震活动性较强,尤其8级以上强震发生频次大幅增加;2021年地震灾害造成的伤亡有所增加,且灾害地震呈现频度高、伤亡集中、次生灾害频发等特征。针对地震频度高、伤亡原因突出的情况,本文提出了相应的地震灾害预防措施及建议, 强调未来地震防御工作至关重要。      

2020年全球地震灾害概要

利用多方收集到的地震灾害资料,对2020年全球地震活动及地震灾害进行了整理,绘制了近20年全球灾害地震频度与伤亡情况变化曲线及2020年灾害地震分布图,描述了造成人员伤亡的地震信息及灾害情况,对重大地震灾害事件做了详细分析,并总结了2020年地震灾害的主要特征.与往年全球地震相比,2020年全球地震活动性较弱,6级以上...     

Variations of the geomagnetic field and the geomagnetic effects of three earthquakes ( M s>5.0) in Jiangsu Province, China

Since 1979 the repeated observations and experiments of geomagnetic total intensity and vertical component have been carried out for ten years in the geomagetic network which is located in Jiangsu Province, China. Three earthquakes aboveM _s 5.0 occurred during the decade, and some seismomagnetic effects were observed. The observation results show that the anomalies of the vertical geomagnetic component can’t be observed untill some months before the earthquake (M _s>5.0) in this area. In this paper it is suggested that a densely distributed network for continuous observation of geomagnetic vertical component may catch seismomagnetic anomalies and thus improve earthquake prediction in the light of the geomagnetic measurements of the mid — or — low latitude locations. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 80–87, 1991. This study is sponsored by the Chinese Joint Seismological Science Foundation.     

Diurnal periodicity of earthquakes and its seasonal variations

Analysis of earthquake catalogues on 14 world regions has revealed a distinct diurnal periodicity of seismic events in all of them. The amplitude of the diurnal variations usually decreases with an increase in earthquake energy, although in some regions, the time series of strong earthquakes also demonstrate diurnal periodicity. Earthquakes are more frequent at night. The acrophase of the course of diurnal seismicity correlates with geographic longitude. The Rayleigh — Schuster hodographs of diurnal periodicity demonstrate sharp changes (kinks) in the vicinity of the equinox and solstice moments. The annual hodograph of the diurnal periodicity of earthquakes is distinctly divided by the equinox moments into segments with different slopes. The defined segments differ in the amplitude and acrophase of the course of diurnal seismicity. The data imply influence of the mutual positions of the Sun and Earth on seismicity in different world regions. Possible mechanisms responsible for such influence are discussed.     

2000年全世界地震灾害综述

2000年全世界地震活动水平略高于往年，但地震灾情很轻，地震死亡人数总计240人，伤3096人，经济损失约3亿美元，2000年印度尼西亚是地震灾害最严重的国家。     

山地地形对地震动放大作用的机理探讨

从震后的调查和监测中发现,大地震会对山区地形形成的地质灾害,山地的局部位置,地震动加速度显著放大,甚至能使大型石块高速临空抛射,该文从地震波在介质中传播的角度,通过分析不同入射角度和不同反射界面地震波的反射叠加情况初步解释这一放大作用产生的机理,得出结论：（1）山地地形是产生地震动放大效应的主要原因;（2）放大效应与山体坡度密切相关（3）山脉走向会影响地震动水平分量的差异。并基于此对山区地形的震害防御工作提出建议。     

2008年世界地震灾害综述

摘要2008年全球地震活动为中等水平,但地震灾情较重。地震死亡和失踪人数总计88223人。伤374171人。经济损失8500亿元。重大地震灾害发生在中国。四川I汶川8级地震是中国自唐山地震以来最严重的震灾。     

Seismicity and stress state in the South China Sea, Indochina and their vicinity

The distribution of earthquakes from 1973 to 1982 in the South China Sea, Indochina and their vicinity was studied using the data from I. S. C. It was found that the earthquakes are mainly concentrated along the boundaries of plates. Beside, some of shallow eartqhuakes are distributed in west part of Burma and the boundary between Burma and China, a few of earthquakes occurred in South China Sea. The features of Benioff zone along the boundaries between India plate, Philippine Sea plate and Eurasia plate were studied. The plate do not coupled well under the Java trench and the Philippine trench. The subducted India plate under Burmese range, Andaman—Nicobar arc moves NNE. The fault plane solutions of earthquakes were studied using the first motions of P wave. The stress state on subduction zones and within the area were deduced from the fault plane solutions and the fault movement. It was found that the direction of principal compression axis of stress is in the NNE in west part of Burma, in S—N in south and middle part of Bruma and Thailand, and in NNE or S—N in the South China Sea. It was also found that the stress state has close relation with the interaction of plates. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 129–137, 1991.