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Aftershock identification  [PDF]
Ilya Zaliapin,Andrei Gabrielov,Vladimir Keilis-Borok,Henry Wong
Physics , 2007, DOI: 10.1103/PhysRevLett.101.018501
Abstract: Earthquake aftershock identification is closely related to the question "Are aftershocks different from the rest of earthquakes?" We give a positive answer to this question and introduce a general statistical procedure for clustering analysis of seismicity that can be used, in particular, for aftershock detection. The proposed approach expands the analysis of Baiesi and Paczuski [PRE, 69, 066106 (2004)] based on the space-time-magnitude nearest-neighbor distance $\eta$ between earthquakes. We show that for a homogeneous Poisson marked point field with exponential marks, the distance $\eta$ has Weibull distribution, which bridges our results with classical correlation analysis for unmarked point fields. We introduce a 2D distribution of spatial and temporal components of $\eta$, which allows us to identify the clustered part of a point field. The proposed technique is applied to several synthetic seismicity models and to the observed seismicity of Southern California.
Spatiotemporal correlations of aftershock sequences  [PDF]
Tiago P. Peixoto,Katharina Doblhoff-Dier,J?rn Davidsen
Physics , 2010, DOI: 10.1029/2010JB007626
Abstract: Aftershock sequences are of particular interest in seismic research since they may condition seismic activity in a given region over long time spans. While they are typically identified with periods of enhanced seismic activity after a large earthquake as characterized by the Omori law, our knowledge of the spatiotemporal correlations between events in an aftershock sequence is limited. Here, we study the spatiotemporal correlations of two aftershock sequences form California (Parkfield and Hector Mine) using the recently introduced concept of "recurrent" events. We find that both sequences have very similar properties and that most of them are captured by the space-time epidemic-type aftershock sequence (ETAS) model if one takes into account catalog incompleteness. However, the stochastic model does not capture the spatiotemporal correlations leading to the observed structure of seismicity on small spatial scales.
Electromagnetic coseismic effect associated with aftershock of Wenchuan M_s8.0 earthquake
汶川地震强余震的电磁同震效应

汤吉,詹艳,王立凤,董泽义,赵国泽,徐建郎
地球物理学报 , 2010,
Abstract: 汶川5.12大地震发生后,在武都汉王地震台及其附近地区布置了2个大地电磁测深点,进行了两期余震序列的地震电磁效应连续监测,共观测到M_s4.0及以上的余震事件35次.通过与汉王强震台的地震记录数据中15个强震记录比较发现,与地震波相对应的地震同震电磁信号存在于所有的电场和磁场记录分量中,它们与地震波到达同步.地震破裂发生时的电磁辐射信号在记录数据中相比地震波达到观测点的电磁信号幅度要小得多,无法从观测数据识别出来.通过分析对比地震位移和同震电磁信号的关系,提出了地震电磁同震信号产生的地震波驱动机理,认为观测系统在地球基本磁场中随地面运动产生了地震同震电磁信号,并从观测的地震振动位移和电磁信号进行了验证.
Interseismic deformation across the Longmenshan fault zone before the 2008 M8.0 Wenchuan earthquake
2008年汶川8.0级地震前横跨龙门山断裂带的震间形变

DU Fang,WEN Xue-Ze,ZHANG Pei-Zhen,WANG Qing-Liang,
杜方

地球物理学报 , 2009,
Abstract: 利用区域GPS和水准测量资料,结合地震构造背景的分析,本文研究2008年汶川8.0级地震前横跨龙门山断裂带地区的震间地壳形变,探讨引起这种形变的活动构造与动力学模式,并由此认识汶川地震的孕育与成因机制.主要结果表明:1997~2007年期间,自龙门山断裂带中段朝北西约230 km的地带内存在垂直于断裂的水平缩短变形、以及平行于断裂的水平右旋剪切变形,缩短率为1.3×10-8/a (即:0.013 mm/km/a),角变形速率为2.6×10-8/a;同一地带在1975~1997年期间还表现出垂直上隆变形,上隆速率在龙门山前山断裂与中央断裂之间仅0.6 mm/a,而至龙门山后山断裂及其以西达2~3 mm/a.这些反映了在汶川地震之前至少10~30余年,龙门山断裂带中段的前山与中央断裂业已闭锁、并伴有应变积累.造成这种形变的主要原因是:以壳内的低速层为“解耦”带,巴颜喀拉地块上地壳朝南东的水平运动在四川盆地西缘受到华南地块的阻挡、转换成龙门山断裂带中段的逆冲运动;由于该断裂段的震间闭锁,致使西侧的巴颜喀拉地块的上地壳发生横向缩短以及平行断裂的右旋剪切变形.然而,龙门山断裂带北段在1997~2007年期间除了有大约0.9 mm/a的右旋剪切变形外,横向的缩短变形极微弱,这可能与该断裂段西侧的岷江、虎牙、龙日坝等断裂带吸收了巴颜喀拉地块朝东水平运动的大部分有关.另外,汶川地震前,横跨龙门山断裂带中段与北段的地壳形变特征的差异,与汶川地震时能量释放的空间分布吻合.
Temporal characteristics of some aftershock sequences in Bulgaria
S. Simeonova,D. Solakov
Annals of Geophysics , 1999, DOI: 10.4401/ag-3763
Abstract: We apply statistical analysis to study the temporal distribution of aftershocks in aftershock sequences of five earthquakes which occurred in Bulgaria. We use the maximum likelihood method to estimate the parameters of the modified Omori formula for aftershock sequences which is directly based on a time series. We find that: the maximum likelihood estimates of the parameter p show a regional variation, with lower values of the decay rate in North Bulgaria; the modified Omori formula provides an appropriate representation of temporal variation of the aftershock activity in North Bulgaria; the aftershock sequences in South Bulgaria are best modeled by the combination of an ordinary aftershock sequence with secondary aftershock activity. A plot of the cumulative number of events versus the frequency-linearized time t clearly demonstrates a transition from aftershock to foreshock activity prior to the second 1986 Strazhitsa (North Bulgaria) earthquake.
A model for complex aftershock sequences  [PDF]
Y. Moreno,A. Correig,J. B. Gomez,A. F. Pacheco
Physics , 2000, DOI: 10.1029/2000JB900396
Abstract: The decay rate of aftershocks is commonly very well described by the modified Omori law, $n(t) \propto t^{-p}$, where n(t) is the number of aftershocks per unit time, t is the time after the main shock, and p is a constant in the range 0.9
The time distribution of aftershock magnitudes, fault geometry and aftershock prediction  [PDF]
Pathikrit Bhattacharya,Kamal,Bikas K. Chakrabarti
Physics , 2009,
Abstract: We have analyzed, for the first time, the time cumulant of magnitudes of an aftershock sequence since the mainshock. This comes out to be a remarkable straight line whose slope is characteristic of the fault zone. This will provide an useful tool in understanding the temporal distribution of aftershocks after a specific mainshock.
A statistical study of aftershock sequences  [cached]
Giorgio Ranalli
Annals of Geophysics , 2010, DOI: 10.4401/ag-4645
Abstract: A comprehensive statistical study of the phenomenology of aftershock sequences is made in this paper. The spatial distribution of aftershocks indicates that they are mainly crustal events; however, deeper sequences also take place. The analysis of the distribution of aftershocks in 15 sequences with respect to time and magnitude leads to the statistical confirmation of a set of phenomenological laws describing the process, namely, the time-frequency law of hyperbolic decay of aftershock activity with time, the magnitude stability law, and the exponential magnitude- frequency distribution. The hypotheses involved are checked. The grouping of data and the statistical methods employed are chosen according to some basic well·confirmed assumptions regarding the nature of the process.
新汶煤田汶南井田滑动构造发育规律  [PDF]
胡绍祥
煤田地质与勘探 , 2003,
Abstract: 简述了滑动构造在山东研究的现状,总结了汶南井田地层结构、地质构造特征及滑动构造对煤矿生产影响的情况,研究了滑动构造在汶南井田的发育规律,结合汶南井田滑动构造发育的特点,提出了该滑动构造发育的邻近规律,并根据这些规律,预测了滑动构造对汶南井田11煤层及13煤层开采的影响。
Rheology of the Tectonosphere as Inferred from Seismic Aftershock Sequences
G. RANALLI,A. E. SCHEIDEGGER
Annals of Geophysics , 1969, DOI: 10.4401/ag-5092
Abstract: Some rheological models of the mechanism of aftershock occurrence, namely, Benioff's, Pshennikov's, and Mogi's models, are examined in the light of the established laws governing the phenomenology of the process. It is concluded that none of them explains fully the aftershock mechanism. Thus, a new creep model is proposed, according to which aftershocks are the discontinuous manifestation of the overall plastic creep by which the rock readjusts itself to the stress distribution left by the main shock. The creep model affords a new large-scale picture of the rheology of the tectonosphere.
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