共查询到20条相似文献，搜索用时 31 毫秒
1.
—The recurrence behaviour of large earthquakes, in several tectonic settings, has been explained by simple models of stress accumulation and release which assume that the fault stress state is solely a function of the far-field tectonic strain rate. However, the limited dataset of large event recurrence intervals has been a major obstacle to the verification of these and other models. We present the results from a simple analogue model of earthquake rupture and stick-slip which displays power-law frequency-size statistics and involves many cycles of large events. We show that, despite the macroscopic homogeneity of the model, large events do not conform to simple deterministic time- or slip-predictable patterns. However, when the recurrence intervals for large events are divided by the median recurrence interval, the normalized data are composed of two distinct lognormally distributed populations. One population is characterized by events which are strongly clustered in time with relatively short recurrence intervals and low moment release, the other by events which are weakly clustered in time with median-sized recurrence intervals. It is suggested that the long-term recurrence behaviour of large earthquakes, whilst being non-deterministic, may be modelled by a well-defined statistical distribution of recurrence intervals. 相似文献
2.
A. Joshi 《Journal of Seismology》2000,4(2):143-160
The rupture plane for an earthquake has been modelledby using the semi empirical technique of Midorikawa(1993). This technique estimates ground accelerationby modelling the rupture process during an earthquake.Modifications in this technique have been made for itsapplication to the Indian region. This has been tested forthe Uttarkashi earthquake of 20th Oct, 1991, India, whichwas well recorded at thirteen stations of installedstrong motion array in this region. After testingseveral possible rupture models, a final model has beenselected and peak ground acceleration due to thismodel is simulated at thirteen different stations.Dependency of methodology on model parameters, e.g.dip and mode of rupture propagation have also beenstudied in detail.Using this technique synthetic isoseismal maps wereprepared by converting peak ground acceleration intoMMI scale. Dependency of rupture models on syntheticisoseismals has also been studied in detail. Usingthis method, peak ground acceleration for the Laturearthquake of Sept 30, 1993 has been obtained atvarious places within meisoseismal area. Synthetic andfield intensity was compared at various well-knownsites. Since the region was not covered by anyinstrumental array during Latur earthquake, thesimulated peak ground accelerations are expected toserve basis of design criteria in this region. 相似文献
3.
Deterministic and probabilistic seismic hazard analyses should be complementary, in the sense that probabilistic analysis may be used to identify the controlling deterministic design‐level earthquake events, and more sophisticated models of these events may then be developed to account for uncertainties that could not have been included directly in the probabilistic analysis. De‐aggregation of the tentative uniform hazard spectra (UHS) in Hong Kong resulting from a probabilistic seismic hazard assessment (PSHA) indicates that strong and major distant earthquakes, rather than moderate local earthquakes, make the largest contribution to the seismic hazard level within the natural‐period range longer than 0.3 s. Ground‐motion simulations of controlling events located 90 and 340 km from Hong Kong, taking into account uncertainties in the rupture process, reveal that the tentative UHS resulting from the PSHA may have significantly underestimated the mid‐to‐long period components. This is attributed mainly to the adoption of double‐corner source‐spectrum models in the attenuation relationships employed in the PSHA. The results of the simulations indicate clearly that rupture directivity and rupture velocity can significantly affect the characteristics of ground motions, even from such distant earthquakes. The rupture‐directivity effects have profound implications in elongating the second corner period where the constant velocity intersects the constant displacement, thus increasing the associated displacement demand. However, demands for acceleration and velocity are found to be not sensitive to the presence of the directivity pulses. Ground pulses resulting from forward rupture directivity of distant earthquakes have longer predominant periods than the usual near‐fault directivity pulses. These long‐period pulses may have profound implications for metropolises, such as Hong Kong and others in Southeast Asia, having large concentration of high‐rise buildings. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
4.
A simple hybrid approach for the simulation of strong ground motion is presented in this paper. This approach is based on
the deterministic modelling of rupture plane initially started by Midorikawa, Tectonophysics 218:287–295, (1993) and further
modified by Joshi, Pure Appl Geophys (PAGEOPH) 8:161, (2004). In this technique, the finite rupture plane of the target event
is divided into several subfaults, which satisfy scaling relationship. In this paper, simulation of strong ground motion due
to a rupture buried in a earth medium consisting of several layers of different velocities and thicknesses is made by considering
(1) transmission of energy at each layer; (2) frequency filtering properties of medium and earthquake source; (3) correction
factor for slip of large and small magnitude earthquakes and (4) site amplification ratio at various stations. To test the
efficacy of the developed technique, strong motion records were simulated at different stations that have recorded the 2004
Niigata-ken Chuetsu, Japan earthquake (M
s 7.0). Comparison is made between the simulated and observed velocity and acceleration records and their response spectra.
Distribution of peak ground acceleration, velocity and displacement surrounding the rupture plane is prepared from simulated
and observed records and are compared with each other. The comparison of synthetic with the observed records over wide range
of frequencies shows that the present technique is effective to predict various strong motion parameters from simple deterministic
model which is based on simple regression relations and modelling parameters. 相似文献
5.
Tunnels are believed to be rather “insensitive” to earthquakes. Although a number of case histories seem to favor such an argument, failures and collapses of underground
structures in the earthquakes of Kobe (1995), Düzce–Bolu (1999), and Taiwan (1999) have shown that there are exceptions to
this “rule”. Among them: the case of tunnels crossed by fault rupture. This paper presents the analysis and design of two highway cut-and-cover
tunnels in Greece against large tectonic dislocation from a normal fault. The analysis, conducted with finite elements, places
particular emphasis on realistically modeling the tunnel-soil interface. Soil behavior is modeled thorough an elastoplastic
constitutive model with isotropic strain softening, which has been extensively validated through successful predictions of
centrifuge model tests. A primary conclusion emerging from the paper is that the design of cut-and-cover structures against
large tectonic deformation is quite feasible. It is shown that the rupture path is strongly affected by the presence of the
tunnel, leading to development of beneficial stress-relieving phenomena such as diversion, bifurcation, and diffusion. The
tunnel may be subjected either to hogging deformation when the rupture emerges close to its hanging-wall edge, or to sagging deformation when the rupture is near its footwall edge. Paradoxically, the maximum stressing is not always attained with
the maximum imposed dislocation. Therefore, the design should be performed on the basis of design envelopes of the internal
forces, with respect to the location of the fault rupture and the magnitude of dislocation. Although this study was prompted by the needs of a specific project, the method of analysis,
the design concepts, and many of the conclusions are sufficiently general to merit wider application. 相似文献
6.
本文基于Haskell的3源辐射谱模型,加上介质非弹性吸收项,几何扩散项和自由面放大效应,推演出峰值加速度和均方根加速度表达式。据此,建议一种考虑震源破裂方向的地震动衰减模型。用Morgan Hill和Imperial Valley两地震的峰值加速度资料,单震级统计分析结果表明,文中建议的地震动衰减模型是合理的。与Joyner和Boore所用的衰减模型相比较,剩余标准差可减少0.1——0.2。本文所考虑的震源破裂的地震动衰减模型,可分别用于不同断层类型的地震,如单侧和双侧走滑型地震及倾滑型地震,分别建立地震动衰减关系,进行地震危险性分析。文章最后给出了美国西部考虑震源破裂方向的地震动峰值加速度和均方根加速度的衰减关系。 相似文献
7.
采用美国南加州地震委员会（SCEC）Steven Day博士提供的三维有限差分断层瞬态破裂动力学模型（3D-FDM）,以1976年唐山MS7.8地震为例,从简化的断层双侧破裂模式出发,对该地震发震断层的动态破裂过程及近断层地表运动特征进行了仿真模拟和计算.研究区域为围绕发震断层200 km×140 km×40 km（深度）的长方形块体组成,模拟计算的空间分辨率和时间分辨率分别为200 m和0.012 s,形成的空间网格节点数为1051×701×201.在DELL小型工作站上,我们实现了对源程序的移植和并行计算.同时,通过引进计算机可视化技术,对模拟数据进行了3D/4D解释分析.另外,在对源程序修改过程中,实现了对京津唐地区三维地壳速度结构的嵌入,在一定程度上增强了对地震波传播以及地面运动模拟的真实性,并讨论了地震破裂的方向性对近断层地表运动的影响.最后根据初步研究结果结合京津唐地区活动断层构造特征,对唐山MS7.8级主震后随之而来的1976滦县MS7.1级余震及宁河MS6.9级余震的动态触发机制提出了新的解释.由于受主震破裂方向性作用的影响,使得主震对后续两个较大余震产生的动态应力变化的峰值在断层的走滑方向上较大,为2~3 MPa,在逆冲方向上较小,为0.1~0.2 MPa.即唐山主震的发生使得其周边的应力场有一个瞬态的应力调整,唐山主震对后续余震的发生有促发作用. 相似文献
8.
采用美国南加州地震委员会(SCEC)Steven Day博士提供的三维有限差分断层瞬态破裂动力学模型(3D-FDM),以1976年唐山M_S7.8地震为例,从简化的断层双侧破裂模式出发,对该地震发震断层的动态破裂过程及近断层地表运动特征进行了仿真模拟和计算.研究区域为围绕发震断层200 km×140 km×40 km(深度)的长方形块体组成,模拟计算的空间分辨率和时间分辨率分别为200 m和0.012 s,形成的空间网格节点数为1051×701×201.在DELL小型上作站上,我们实现了对源程序的移植和并行计算.同时,通过引进计算机可视化技术,对模拟数据进行了3D/4D解释分析.另外,在对源程序修改过程中,实现了对京津唐地区三维地壳速度结构的嵌入,在一定程度上增强了对地震波传播以及地面运动模拟的真实性,并讨论了地震破裂的方向性对近断层地表运动的影响.最后根据初步研究结果结合京津唐地区活动断层构造特征,对唐山M_S7.8级主震后随之而来的1976滦县M_S7.1级余震及宁河M_S6.9级余震的动态触发机制提出了新的解释.由于受主震破裂方向性作用的影响,使得主震对后续两个较大余震产生的动态应力变化的峰值在断层的走滑方向上较大,为2～3 MPa,在逆冲方向上较小,为0.1～0.2 MPa.即唐山主震的发生使得其周边的应力场有一个瞬态的应力调整,唐山主震对后续余震的发生有促发作用. 相似文献
9.
利用2001年昆仑山口西MS8.1地震现场观测所提供的地表破裂同震位移数据,使用简单滑移弱化破裂模型,估算了发震主断层上的破裂传播速度. 该模型中考虑了断层破裂时动摩擦过程中应力上调和下调机制对地震波辐射能量分配的影响. 对比Bouchon和Valleacute;e有关昆仑山口西地震主断层破裂传播速度超过剪切波速度,甚至达到P波速度的结果, 采用动摩擦应力下调时的滑移弱化模型 (分数应力降模型),结果表明,伴随较高的地震波辐射效率,主断层的平均破裂传播速度等于或小于瑞利波速度,这与许力生和陈运泰的体波反演结果,以及陈学忠震源应力场估算的结果是一致的. 最后,联系到由地表破裂现象所反映出的断层力学特征,如与视应力相关的分数应力降 (动摩擦应力下调), 基于滑移弱化模型, 讨论了可能的震源破裂机制. 相似文献
10.
With co-seismic surface rupture slip displacements provided by the field observation for the 2001 MS8.1 West Kunlun Mountain Pass earthquake, this paper estimates the rupture speed on the main faulting segment with a long straight fault trace on the surface based on a simple slip-weakening rupture model, in which the frictional overshoot or undershoot are involved in consideration of energy partition during the earthquake faulting. In contrast to the study of Bouchon and Vallée, in which the rupture propagation along the main fault could exceed the local shear-wave speed, perhaps reach the P-wave speed on a certain section of fault, our results show that, under a slip-weakening assumption combined with a frictional undershoot (partial stress drop model), average rupture speed should be equal to or less than the Rayleigh wave speed with a high seismic radiation efficiency, which is consistent with the result derived by waveform inversion and the result estimated from source stress field. Associated with the surface rupture mechanism, such as partial stress drop (frictional undershoot) associated with the apparent stress, an alternative rupture mechanism based on the slip-weakening model has also been discussed. 相似文献
11.
Convergence of deterministic and stochastic approaches in optimal remediation design of a contaminated aquifer 总被引：2，自引：2，他引：0
Nak-Youl Ko Kang-Kun Lee 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(3):309-318
The comparison between two series of optimal remediation designs using deterministic and stochastic approaches showed a number
of converging features. Limited sampling measurements in a supposed contaminated aquifer formed the hydraulic conductivity
field and the initial concentration distribution used in the optimization process. The deterministic and stochastic approaches
employed a single simulation–optimization method and a multiple realization approach, respectively. For both approaches, the
optimization model made use of a genetic algorithm. In the deterministic approach, the total cost, extraction rate, and the
number of wells used increase when the design must satisfy the intensified concentration constraint. Growing the stack size
in the stochastic approach also brings about same effects. In particular, the change in the selection frequency of the used
extraction wells, with increasing stack size, for the stochastic approach can indicate the locations of required additional
wells in the deterministic approach due to the intensified constraints. These converging features between the two approaches
reveal that a deterministic optimization approach with controlled constraints is achievable enough to design reliable remediation
strategies, and the results of a stochastic optimization approach are readily available to real contaminated sites. 相似文献
12.
A. W. Jayawardena P. C. Xu W. K. Li 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(7):863-877
In many regions, monthly (or bimonthly) rainfall data can be considered as deterministic while daily rainfall data may be
treated as random. As a result, deterministic models may not sufficiently fit the daily data because of the strong stochastic
nature, while stochastic models may also not reliably fit into daily rainfall time series because of the deterministic nature
at the large scale (i.e. coarse scale). Although there are different approaches for simulating daily rainfall, mixing of deterministic
and stochastic models (towards possible representation of both deterministic and stochastic properties) has not hitherto been
proposed. An attempt is made in this study to simulate daily rainfall data by utilizing discrete wavelet transformation and
hidden Markov model. We use a deterministic model to obtain large-scale data, and a stochastic model to simulate the wavelet
tree coefficients. The simulated daily rainfall is obtained by inverse transformation. We then compare the accumulated simulated
and accumulated observed data from the Chao Phraya Basin in Thailand. Because of the stochastic nature at the small scale,
the simulated daily rainfall on a point to point comparison show deviations with the observed data. However the accumulated
simulated data do show some level of agreement with the observed data. 相似文献
13.
Gaetano Zonno Roberto Basili Fabrizio Meroni Gemma Musacchio P. Martin Mai Gianluca Valensise 《Bulletin of Earthquake Engineering》2012,10(4):1075-1107
We present a strategy for obtaining fault-based maximum observable shaking (MOS) maps, which represent an innovative concept for assessing deterministic seismic ground motion at a regional scale. Our approach uses the fault sources supplied for Italy by the Database of Individual Seismogenic Sources, and particularly by its composite seismogenic sources (CSS), a spatially continuous simplified 3-D representation of a fault system. For each CSS, we consider the associated Typical Fault, i.e., the portion of the corresponding CSS that can generate the maximum credible earthquake. We then compute the high-frequency (1–50?Hz) ground shaking for a rupture model derived from its associated maximum credible earthquake. As the Typical Fault floats within its CSS to occupy all possible positions of the rupture, the high-frequency shaking is updated in the area surrounding the fault, and the maximum from that scenario is extracted and displayed on a map. The final high-frequency MOS map of Italy is then obtained by merging 8,859 individual scenario-simulations, from which the ground shaking parameters have been extracted. To explore the internal consistency of our calculations and validate the results of the procedure we compare our results (1) with predictions based on the Next Generation Attenuation ground-motion equations for an earthquake of Mw 7.1, (2) with the predictions of the official Italian seismic hazard map, and (3) with macroseismic intensities included in the DBMI04 Italian database. We then examine the uncertainties and analyse the variability of ground motion for different fault geometries and slip distributions. 相似文献
14.
15.
《Advances in water resources》1998,21(6):463-475
This paper describes a methodology, based on dynamical systems theory, to model and predict streamflow at the daily scale. The model is constructed by developing a multidimensional phase-space map from observed streamflow signals. Predictions are made by examining trajectories on the reconstructed phase space. Prediction accuracy is used as a diagnostic tool to characterize the nature, which ranges from low-order deterministic to stochastic, of streamflow signals. To demonstrate the utility of this diagnostic tool, the proposed method is first applied to a time series with known characteristics. The paper shows that the proposed phase-space model can be used to make a tentative distinction between a noisy signal and a deterministic chaotic signal.The proposed phase-space model is then applied to daily streamflow records for 28 selected stations from the Continental United States covering basin areas between 31 and 35 079 km2. Based on the analyses of these 28 streamflow time series and 13 artificially generated signals with known characteristics, no direct relationship between the nature of underling stream flow characteristics and basin area has been found. In addition, there does not appear to be any physical threshold (in terms of basin area, average flow rate and yield) that controls the change in streamflow dynamics at the daily scale. These results suggest that the daily streamflow signals span a wide dynamical range between deterministic chaos and periodic signal contaminated with additive noise. 相似文献
16.
计算机仿真模拟设定地震断层动态破裂传播和近断层强地表运动响应的结果表明, 对于特征地震而言,近断层附近的地表运动特征与断层破裂传播的方向性有着强烈的依赖关系. 当场地（观测点）至断层的距离给定时,正向于破裂传播方向的场地（场地A）的地表质点运动（位移、速度、加速度）,远远大于震中附近（场地B）和反向于破裂传播方向的场地（场地C）的地表质点运动,而且沿断层垂直分量所辐射的SH波的传播起到了主导作用. 对应于场地A,B和C,统计分析结果表明,峰值加速度的几何平均值之比为2.15:1.5:1, 而且各自的均方差分别为0.12, 0.11和0.13. 如果将所得的研究结果应用于概率地震危险性分析中,对于较低的年超越频度,近断层附近的地表峰值加速度的估算值可下降15%~30%. 因此,考虑到断层破裂传播方向性对地表运动的影响,区域衰减曲线的回归分析模型应该给予恰当的修正. 相似文献
17.
Use of Seismotectonic Information for the Seismic Hazard Analysis for Surat City, Gujarat, India: Deterministic and Probabilistic Approach 总被引：1，自引：0，他引：1
T. P. Thaker Ganesh W. Rathod K. S. Rao K. K. Gupta 《Pure and Applied Geophysics》2012,169(1-2):37-54
Surat, the financial capital of Gujarat, India, is a mega city with a population exceeding five millions. The city falls under Zone III of the Seismic Zoning Map of India. After the devastating 2001 Bhuj earthquake of Mw 7.7, much attention is paid towards the seismic microzonation activity in the state of Gujarat. In this work, an attempt has been made to evaluate the seismic hazard for Surat City (21.170?N, 72.830?E) based on the probabilistic and deterministic seismic hazard analysis. After collecting a catalogue of historical earthquakes in a 350?km radius around the city and after analyzing a database statistically, deterministic analysis has been carried out considering known tectonic sources; a further recurrence relationship for the control region is found out. Probabilistic seismic hazard analyses were then carried out for the Surat region considering five seismotectonic sources selected from a deterministic approach. The final results of the present investigations are presented in the form of peak ground acceleration and response spectra at bed rock level considering the local site conditions. Rock level Peak Ground Acceleration (PGA) and spectral acceleration values at 0.01?s and 1.0?s corresponding to 10% and 2% probability of exceedance in 50 years have been calculated. Further Uniform Hazard Response Spectrum (UHRS) at rock level for 5% damping, and 10% and 2% probability of exceedance in 50 years, were also developed for the city considering all site classes. These results can be directly used by engineers as basic inputs in earthquake-resistant design of structures in and around the city. 相似文献
18.
As a deterministic numerical approach for simulation of earthquake ground motions, the spectral element method (SEM) is applied to generate a broadband acceleration array for dam-canyons instead of the traditional empirical or stochastic methods. Specifically, the SEM analysis model with an extra fine mesh is used for the Pacoima Canyon to simulate the entire path starting from earthquake source rupture via the propagation medium to the local site. The source and the 3D earth model (velocity structure) are validated through the modeling of the Newhall earthquake on 28 October 2012 at a frequency of up to 8 Hz. Subsequently, the San Fernando earthquake records on 13 January 2001 are further used to study the effects of propagation path in simulation. Finally, the spatially varying ground motions at the Pacoima Canyon are obtained for different source mechanisms. The results show that the source mechanism and the local site topography significantly affect the distribution of the peak accelerations along the canyon. 相似文献
19.
Sohan Lal A. Joshi Sandeep Monu Tomer Parveen Kumar Chun-Hsiang Kuo Che-Min Lin Kuo-Liang Wen M. L. Sharma 《Acta Geophysica》2018,66(4):461-477
On 25th April, 2015 a hazardous earthquake of moment magnitude 7.9 occurred in Nepal. Accelerographs were used to record the Nepal earthquake which is installed in the Kumaon region in the Himalayan state of Uttrakhand. The distance of the recorded stations in the Kumaon region from the epicenter of the earthquake is about 420–515 km. Modified semi-empirical technique of modeling finite faults has been used in this paper to simulate strong earthquake at these stations. Source parameters of the Nepal aftershock have been also calculated using the Brune model in the present study which are used in the modeling of the Nepal main shock. The obtained value of the seismic moment and stress drop is 8.26 × 1025 dyn cm and 10.48 bar, respectively, for the aftershock from the Brune model .The simulated earthquake time series were compared with the observed records of the earthquake. The comparison of full waveform and its response spectra has been made to finalize the rupture parameters and its location. The rupture of the earthquake was propagated in the NE–SW direction from the hypocenter with the rupture velocity 3.0 km/s from a distance of 80 km from Kathmandu in NW direction at a depth of 12 km as per compared results. 相似文献
20.
Development of attenuation relation for the near fault ground motion from the characteristic earthquake 总被引：1，自引：0，他引：1
A composite source model has been used to simulate a broadband strong ground motion with an associated fault rupture process. A scenario earthquake fault model has been used to generate 1 000 earthquake events with a magni-tude of Mw8.0. The simulated results show that, for the characteristic event with a strike-slip faulting, the character istics of near fault ground motion is strongly dependent on the rupture directivity. If the distance between the sites and fault was given, the ground motion in the forward direction (Site A) is much larger than that in the backward direction (Site C) and that close to the fault (Site B). The SH waves radiated from the fault, which corresponds to the fault-normal component plays a key role in the ground motion amplification. Corresponding to the sites A, B, and C, the statistical analysis shows that the ratio of their aPG is 2.15:1.5:1 and their standard deviations are about 0.12, 0.11, and 0.13, respectively. If these results are applied in the current probabilistic seismic hazard analysis (PSHA), then, for the lower annual frequency of exceedance of peak ground acceleration, the predicted aPG from the hazard curve could reduce by 30% or more compared with the current PSHA model used in the developing of seismic hazard map in the USA. Therefore, with a consideration of near fault ground motion caused by the rupture directivity, the regression model used in the development of the regional attenuation relation should be modified accordingly. 相似文献