Extreme flood events and climate change around 3500 aBP in the Central Plains of China     

XIA Zhengkai  WANG Zanhong & ZHAO Qingchun . College of Environmental Sciences  Peking University  Beijing  China  . Archaeology Research Institute  Chinese Academy of Social Sciences  Beijing  China 《中国科学D辑(英文版)》2004,47(7):599-606

The occurrence of prehistoric extreme flood events has been the common interest of geologists, geographers and archaeologists. It is recognized that from 5000 aBP to 3000 aBP was a period of extreme floods frequently occurring around the world. For in-stance, flood events have been found in North Amer-ica, rapid sea level rise has been found in both the Black Sea and the Mediterranean Sea, and flooded ancient cities have been found in a number of coast areas[1—6]. In China, records of pre…  相似文献   

Characterization of the Frequency of Extreme Earthquake Events by the Generalized Pareto Distribution     

V. F.?PisarenkoEmail author  D.?Sornette 《Pure and Applied Geophysics》2003,160(12):2343-2364

Recent results in extreme value theory suggest a new technique for statistical estimation of distribution tails (Embrechts et al., 1997), based on a limit theorem known as the Gnedenko-Pickands-Balkema-de Haan theorem. This theorem gives a natural limit law for peak-over-threshold values in the form of the Generalized Pareto Distribution (GPD), which is a family of distributions with two parameters. The GPD has been successfully applied in a number of statistical problems related to finance, insurance, hydrology, and other domains. Here, we apply the GPD approach to the well-known seismological problem of earthquake energy distribution described by the Gutenberg-Richter seismic moment-frequency law. We analyze shallow earthquakes (depth h<70 km) in the Harvard catalog over the period 1977–2000 in 12 seismic zones. The GPD is found to approximate the tails of the seismic moment distributions quite well over the lower threshold approximately M 10²⁴ dyne-cm, or somewhat above (i.e., moment-magnitudes larger than m _W =5.3). We confirm that the b-value is very different (b=2.06 ± 0.30) in mid-ocean ridges compared to other zones (b=1.00 ± 0.04) with a very high statistical confidence and propose a physical mechanism contrasting crack-type rupture with dislocation-type behavior. The GPD can as well be applied in many problems of seismic hazard assessment on a regional scale. However, in certain cases, deviations from the GPD at the very end of the tail may occur, in particular for large samples signaling a novel regime.  相似文献   

陆表海盆地海侵事件成煤作用机制分析   总被引：29，自引：4，他引：25  

李增学  余继峰  郭建斌  韩美莲 《沉积学报》2003,21(2):288-296,306

研究了含煤地层中海侵事件沉积序列,即海侵沉积与煤层直接接触的组合特点,总结了海侵事件和海侵事件成煤特点,提出了陆表海聚煤盆地海侵事件成煤作用理论及海侵事件成煤机制。研究表明,陆表海盆地充填沉积序列中,既有海退成煤作用又有海侵成煤作用发生,而且,海侵事件为陆表海盆地海平面变化的典型特色,海侵的突发性是海侵事件的基本属性,其沉积具有等时性。海侵事件导致盆地事件型聚煤作用发生。本文还深入讨论了海侵事件成煤机制及其在含煤地层层序地层界面识别、层序地层单元划分的重要意义和作用。  相似文献   

收集地震参考事件的研究进展   总被引：1，自引：0，他引：1  

徐志国  刘瑞丰 《地震地磁观测与研究》2006,27(3):20-24

简要介绍了参考事件的定义及其分类,并对收集GT5参考事件的理论方法和标准做了简单的说明。文章指出,参考事件的用途主要在于获取经验走时,验证速度模型和计算走时,提供可靠的地震信息。如何收集更多的地震参考事件是当今国际地震学界热衷的研究问题之一。文中讨论了如何在中国大尺度范围内有效地获取GT5参考事件,并希望在中国能尽快地推进此项工作的进行。  相似文献   

安徽巢湖地区泥盆纪-石炭纪界线地层的新认识   总被引：2，自引：1，他引：2  

侯明金  齐敦伦 《地层学杂志》2006,30(2):157-170

通过对研究区内的五通组几条代表性剖面的岩性、岩相及化石特征和地层区域展布等研究并进行区域对比,结合近年来的区调及科研成果,提出巢湖地区五通组观山段至擂鼓台段中部的下黏土层的时代属于晚泥盆世晚期斯图期,而擂鼓台段中部的上黏土层与上部为早石炭世早期杜内期,泥盆系-石炭系界线位于上、下黏土层之间石英砂岩中(狮子口剖面31层的顶面);擂鼓台段下部与中部之间有一沉积间断面,有铁质风化壳,局部见褐铁矿化砾岩层,这一间断面是泥盆纪末期大海退在本区的反映;巢湖地区五通组并非陆相沉积,而是一套海相的滨岸相沉积,海水主要来自北东方向,与过去的陆相沉积和海侵来自南西方向的论点有所不同。  相似文献   

再论塔里木盆地库车坳陷三叠纪-侏罗纪的海泛事件   总被引：1，自引：0，他引：1  

张宝民  陈建平  边立曾  张水昌 《地质学报》2006,80(2):236-244

多年来的油气源对比表明,塔里木盆地库车坳陷的油气来源于三叠系-侏罗系的湖相、湖沼相烃源岩,因而探讨三叠纪-侏罗纪湖盆曾否遭受过特提斯洋海水的海泛,不仅对古地理重建,而且对烃源岩及其生油气潜力评价都具有重要的意义.笔者在该坳陷三叠系-侏罗系湖相烃源岩的生烃母质中发现了大量的各类底栖宏观藻类化石,并获得了沉积地球化学证据.据此,并结合区域古构造-古地貌演变与全球、大区域海平面升降规律的综合判断,初步认为库车坳陷在三叠纪-侏罗纪曾多次受到过特提斯洋短暂海泛的影响,其中规模最大的是晚三叠世黄山街期晚期、早侏罗世阳霞期晚期和中侏罗世恰克马克期.海泛的原因,可能与特提斯洋海平面升高和库车坳陷湖盆区-陆源区地势缓坦的联合作用有关.由于海泛改善了生烃母质类型,从而使海泛层段的源岩氢指数等表征生烃能力的指标有一定提高.  相似文献   

Results of locating the IASPEI GT(0-5) reference events using the standard ISC procedures     

Dmitry A. Storchak 《Physics of the Earth and Planetary Interiors》2006,158(1):4-13

The International Seismological Centre (ISC) is charged with production of the definitive global bulletin of seismic events, based on the most comprehensive set of parametric data collected from all over the world. Almost every event in the bulletin retains the original hypocentral solutions reported to the ISC by contributing agencies. In addition, where possible, the ISC computes its own solution, which is intended to be the most accurate where the data from several networks are used. It is because of the requirement for consistency of the bulletin over the years that the procedures used at the centre to compute hypocentres have remained rather conservative despite considerable advances made in the field of earthquake location.The ISC has developed and put into operation a new data management system. As a result, it is now possible to review and subsequently introduce more up-to-date methods of locating seismic events into the operations. The ISC Governing Council called for a workshop dedicated to location procedures, which was held during the 2005 IASPEI General Assembly in Santiago, Chile.To compare the accuracy of different location algorithms, a list of 156 reference events (IWREF) was selected prior to the workshop. The list includes geographically well distributed earthquakes and explosions with positions known with an accuracy of up to 5 km. It covers the period of 1954-2001 and includes all station readings and hypocentral solutions of different agencies available for these events in the ISC bulletin. Although the original ISC solutions are included, these may be different from the solution obtainable now due to changes in the ISC procedures over the years. This paper presents the results of relocation of these events using standard ISC location procedures as of 2005. These new ISC locations and analysis of their shifts with respect to reference locations present a benchmark for further improvement.  相似文献   

二维地震波场快照放映机制的VC++实现     

孙晟  牛滨华 《物探化探计算技术》2006,28(3):268-271

地震波的传播是一个与时间相关的动态过程,可以通过求解波动方程,分析得到的波场快照来研究地震波传播过程。波场快照的连续放映使得离散数据与时间的相关性得以恢复,有助于全面认识地震波传播过程。这里给出了二维波场快照放映的程序实现过程,提出数据加载并成像到内存设备环境的方法,以及处理定时器消息实现放映的方法,并对快照数据的存储格式和其它数据加载成像方法进行了讨论。基于上述方法,利用VC 的MFC工具编制了一个程序实例,实例的应用效果验证了该方法的有效性。  相似文献   

Statistical analysis of extreme events in a non-stationary context via a Bayesian framework: case study with peak-over-threshold data     

Benjamin Renard  Michel Lang  Philippe Bois 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,21(2):97-112

Statistical analysis of extremes currently assumes that data arise from a stationary process, although such an hypothesis is not easily assessable and should therefore be considered as an uncertainty. The aim of this paper is to describe a Bayesian framework for this purpose, considering several probabilistic models (stationary, step-change and linear trend models) and four extreme values distributions (exponential, generalized Pareto, Gumbel and GEV). Prior distributions are specified by using regional prior knowledge about quantiles. Posterior distributions are used to estimate parameters, quantify the probability of models and derive a realistic frequency analysis, which takes into account estimation, distribution and stationarity uncertainties. MCMC methods are needed for this purpose, and are described in the article. Finally, an application to a POT discharge series is presented, with an analysis of both occurrence process and peak distribution.  相似文献   

Inter-organizational coordination in extreme events: The World Trade Center attacks, September 11, 2001   总被引：1，自引：2，他引：1  

Louise K. Comfort  Naim Kapucu 《Natural Hazards》2006,39(2):309-327

This paper addresses the problem of inter-organizational coordination in response to extreme events. Extreme events require coordinated action among multiple actors across many jurisdictions under conditions of urgent stress, heavy demand and tight time constraints. The problem is socio-technical in that the capacity for inter-organizational coordination depends upon the technical structure and performance of the information systems that support decision making among the participating organizations. Interactions among human managers, computers and organizations under suddenly altered conditions of operation are complex and not well understood. Yet, coordinating response operations to extreme events is an extraordinarily complex task for public and nonprofit managers. This paper will analyze the interactions among public, private and nonprofit organizations that evolved in response to the 11 September 2001 attacks, examining the relationships among organizations in terms of timely access to information and types of supporting infrastructure. The performance of the inter-organizational system is examined in the context of the events of 11 September 2001 from the theoretical perspective of complex adaptive systems. A model of auto-adaptation is proposed for implementation to improve inter- organizational performance in extreme events. This model is based on the concept of individual, organizational and collective learning in environments exposed to recurring risk, guided by a shared goal. Such a model requires public investment in the development of an information infrastructure that can support the intense demand for communication, information search, exchange and feedback that characterizes an auto-adaptive system.  相似文献