Determination of earthquake early warning parameters, τ_c and P_d, for southern California     

Yih-Min Wu  Hiroo Kanamori  Richard M. Allen  Egill Hauksson 《Geophysical Journal International》2007,170(2):711-717

We explore a practical approach to earthquake early warning in southern California by determining a ground-motion period parameter  τ _c   and a high-pass filtered displacement amplitude parameter Pd from the initial 3 s of the P waveforms recorded at the Southern California Seismic Network stations for earthquakes with M > 4.0. At a given site, we estimate the magnitude of an event from  τ _c   and the peak ground-motion velocity ( PGV ) from Pd . The incoming three-component signals are recursively converted to ground acceleration, velocity and displacement. The displacements are recursively filtered with a one-way Butterworth high-pass filter with a cut-off frequency of 0.075 Hz, and a P -wave trigger is constantly monitored. When a trigger occurs,  τ _c   and Pd are computed. We found the relationship between  τ _c   and magnitude ( M ) for southern California, and between Pd and PGV for both southern California and Taiwan. These two relationships can be used to detect the occurrence of a major earthquake and provide onsite warning in the area around the station where onset of strong ground motion is expected within seconds after the arrival of the P wave. When the station density is high, the methods can be applied to multistation data to increase the robustness of onsite early warning and to add the regional warning approach. In an ideal situation, such warnings would be available within 10 s of the origin time of a large earthquake whose subsequent ground motion may last for tens of seconds.  相似文献   

Expected loss‐based alarm threshold set for earthquake early warning systems     

Iunio Iervolino  Massimiliano Giorgio  Gaetano Manfredi 《地震工程与结构动力学》2007,36(9):1151-1168

Earthquake early warning systems (EEWS) seem to have potential as tools for real‐time seismic risk management and mitigation. In fact, although the evacuation of buildings requires warning time not available in many urbanized areas threatened by seismic hazard, they may still be used for the real‐time protection of critical facilities using automatic systems in order to reduce the losses subsequent to a catastrophic event. This is possible due to the real‐time seismology, which consists of methods and procedures for the rapid estimation of earthquake features, as magnitude and location, based on measurements made on the first seconds of the P‐waves. An earthquake engineering application of earthquake early warning (EEW) may be intended as a system able to issue the alarm, if some recorded parameter exceeds a given threshold, to activate risk mitigation actions before the quake strikes at a site of interest. Feasibility analysis and design of such EEWS require the assessment of the expected loss reduction due to the security action and set of the alarm threshold. In this paper a procedure to carry out these tasks in the performance‐based earthquake engineering probabilistic framework is proposed. A merely illustrative example refers to a simple structure assumed to be a classroom. Structural damage and non‐structural collapses are considered; the security action is to shelter occupants below the desks. The cost due to a false alarm is assumed to be related to the interruption of didactic activities. Results show how the comparison of the expected losses, for the alarm‐issuance and non‐issuance cases, allows setting the alarm threshold on a quantitative and consistent basis, and how it may be a tool for the design of engineering applications of EEW. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Characteristics and Genetic Analysis of the Deep-buried Weathered-crust Karst Hydrocarbon Reservoirs of the Lower Paleozoic Group in the Tarim Basin     

GU Jiayu  ZHANG Xingyang  FANG HuiResearch Institute of Petroleum Exploration  Development of PetroChin  Beijing 《《地质学报》英文版》2002,76(4):494-502

The genetic analysis of the deep-buried reservoirs of the Lower Paleozoic carbonate rocks in the Tarim basin is a difficult task involving many factors. Firstly, the object of study is carbonate rocks, which have undergone a long term of modification. Secondly, the rocks are deeply buried with depths of 3800-7000 m in the Tarim basin. The primary reservoir properties formed in the deposition have been strongly modified during the deep burial process. Concurrently, the different burial depths in different areas result in diversities of burial temperature, pressure, underground water, hydrochemistry and various physicochemical changes, which further lead to differences in the diagenetic type, diagenetic property, diagenetic degree and their impacts on the reservoir properties. The Lower Paleozoic Cambrian and Ordovician carbonate reservoirs in the Tarim basin can be grouped into four types, i.e., paleo-weathered-crust reservoirs, reef reservoirs, buried karst reservoirs and dolomite reservoirs. This paper  相似文献   

渝东武隆上寒武统孔隙结构特征及成岩作用研究   总被引：1，自引：1，他引：1       下载免费PDF全文

王志宏  李建明  高振中  罗顺社 《沉积与特提斯地质》2002,22(3):69-73

渝东武隆上寒武统地层，储集空间以次生孔隙为主，包括晶间孔、晶间溶孔、粒内溶孔、粒间溶孔、铸模孔、溶洞、裂缝。成岩作用是影响储集性能的主要因素。研究区成岩作用，依据其对孔缝的影响，以及本组地层特征可分为建设性成岩作用和破坏性成岩作用两种类型，前者包括白云石化作用、溶蚀作用、破裂作用；后者包括胶结作用、压实压溶作用、充填作用。  相似文献   

铁路沿线灾害性天气监测、预测、预警系统   总被引：3，自引：0，他引：3  

叶文军  刘红光等 《沙漠与绿洲气象(新疆气象)》2001,24(6):25-27

针对铁路三防（防风，防沙，防洪）的需要，结合大风监测系统建设的实际，对恶劣天气气候条件下，如何保障列车运行安全进行了探讨，并提出铁路沿线灾害性天气监测，预测，预警系统。  相似文献   

冲积沉积构型单元分析法——原理及其适用性   总被引：7，自引：2，他引：7  

兰朝利  吴峻  张为民  李继亮  何顺利  魏俊芝 《地质科技情报》2001,20(2):37-40

通过对构型单元分析法原理和构型单元界面定义的回顾并结合对延长组的研究，发现构型单元分析法适用于以冲积作用为主要沉积物搬运方式的沉积地层。对岩性呈渐变过程、界面类型单一、界面级别难以确定、成岩改造强烈、同沉积变形发育以及底辟作用强烈的地层，不宜使用构型单元分析法。在河口湾、潮间带和河流三角洲前缘环境中形成的沉积体也不适合进行构型单元分析。  相似文献   

Impact of early diagenesis and bulk particle grain size distribution on estimates of relative geomagnetic palaeointensity variations in sediments from Lama Lake, northern Central Siberia   总被引：1，自引：0，他引：1  

Norbert R. Nowaczyk  Stefanie Harwart  Martin Melles 《Geophysical Journal International》2001,145(1):300-306

  相似文献   

Plagioclase dissolution related to biodegradation of oil in Brent Group sandstones (Middle Jurassic) of Gullfaks Field, northern North Sea   总被引：1，自引：0，他引：1  

S. N. Ehrenberg  & K. G. Jakobsen 《Sedimentology》2001,48(4):703-721

Brent Group sandstones from the north side of the Gullfaks Oilfield contain mostly 5–8% albitic plagioclase, whereas plagioclase is almost absent in the same strata in the southern part of the field. Absence of plagioclase throughout the entire vertical extent of the Brent Group in the southern wells seems to rule out provenance as the principal explanation for differing plagioclase content, which is therefore interpreted as the result of diagenesis. Hypotheses for the nature of the inferred leaching event include epigenetic meteoric diagenesis and mesogenetic release of acid components from clay minerals or kerogen, but these explanations are unable to account for the observed spatial distribution of the plagioclase-bearing and plagioclase-free sandstone intervals. However, overall correspondence between the area lacking plagioclase and oil compositions having both anomalously high CO₂ and organic geochemical indications of advanced biodegradation suggest a link between plagioclase dissolution and biodegradation of the present oil column. It is, therefore, proposed that acid components from biodegradation selectively reacted with albitic plagioclase to form kaolin, releasing sodium bicarbonate into the residual water. The plagioclase-free sandstones contain more kaolin than the plagioclase-bearing sandstones, as would be expected due to aluminium conservation. However, the wide and overlapping ranges of kaolin content in both groups suggest that most of the kaolin originated from processes other than biodegradation-driven plagioclase alteration, potentially including both epigenetic and mesogenetic dissolution, as well as deposition of detrital kaolin and kaolin precursors.  相似文献   

Cryptic sequence boundaries in braided fluvial successions   总被引：2，自引：0，他引：2  

Andrew D. Miall  & Mohamud Arush 《Sedimentology》2001,48(5):971-985

In braided fluvial deposits, consisting of monotonous successions of sandstone or conglomerate, it may be difficult to distinguish regionally significant bounding surfaces (sequence boundaries) from autogenic channel-scour surfaces. Major surfaces may be characterized by erosional relief and draped by lag deposits, but not all sequence boundaries show these characteristics. Other clues to the presence of a major surface are sharp changes in detrital composition, shifts in regional palaeocurrent trends and evidence of early diagenesis of the sandstones immediately below the sequence boundary. Examples of these attributes of cryptic sequence boundaries are illustrated from three Mesozoic units in the Colorado Plateau area of the United States. In the Chinle Formation (Triassic), near Moab, Utah, angular intraformational unconformities overlie sandstones showing evidence of early diagenesis. In the Castlegate Sandstone (Upper Cretaceous) of east-central Utah, a cryptic sequence boundary can be discriminated from other erosion surfaces by the evidence of detrital petrography and early diagenesis. Palaeocurrent data indicate changes in regional palaeoslope at two sequence boundaries within this unit. Evidence of early diagenesis is also present at a sequence boundary in the Kayenta Formation (Jurassic) of westernmost Colorado.  相似文献   

上新世末～更新世初西太平洋变冷事件及其古气候意义          下载免费PDF全文

王律江 《第四纪研究》1996,16(4):300-309

依据深海沉积中浮游有孔虫化石群落，采用时间面与时间系列分析及目标转换函数方法，再造西太平洋近2.6Ma以来表层水温历史。结果表明，上新世末～更新世初，西太平洋曾经历一大幅度、不可逆性质的温降。变冷事件集中发生于2.4～1.0MaB.P.间，主要体现在亚热带水团，冬、夏降温幅度达7～8℃和2-3℃，热带水团相对稳定。西太平洋温度场巨变表明其在北半球冰川发展过程中的正、负反馈作用，并由此奠定了中、晚更新世冰期旋回的全球气候模式。  相似文献