Stochastic earthquake source model for ground motion simulation

In the analysis and design of important structures with relatively long life spans, there is a need to generate strong motion data for possible large events. The source of an earthquake is characterized by the spatial distribution of slip on the fault plane. For future events, this is unknown. In this paper, a stochastic earthquake source model is developed to address this issue. Here, 1D and 2D stochastic models for slip distribution developed by Lavallée et al.(2006) are used. The random field associated with the slip distribution is heavy-tailed stable distribution which can be used for large events. Using 236 past rupture models, the spectral scaling parameter and the four stable or Levy's parameters against empirical relationship for known quantities like magnitude or fault length are developed. The model is validated with data from 411 stations of 1999 Chi-Chi earthquake. The simulated response spectrum showed good agreement to actual data. Further the proposed model is used to generate ground motion for the 1993 Killari Earthquake where strong motion data is not available. The simulated mean peak ground velocity was in turn related to the intensity(MSK) and compared against values in the literature.     

Probabilistic seismic response and reliability assessment of isolated bridges

Bridge seismic isolation strategy is based on the reduction of shear forces transmitted from the superstructure to the piers by two means: shifting natural period and earthquake input energy reduction by dissipation concentrated in protection devices. In this paper, a stochastic analysis of a simple isolated bridge model for different bridge and device parameters is conducted to assess the efficiency of this seismic protection strategy. To achieve this aim, a simple nonlinear softening constitutive law is adopted to model a wide range of isolation devices, characterized by only three essential mechanical parameters. As a consequence of the random nature of seismic motion, a probabilistic analysis is carried out and the time modulated Kanai-Tajimi stochastic process is adopted to represent the seismic action. The response covariance in the state space is obtained by solving the Lyapunov equation for a stochastic linearized system. After a sensitivity analysis, the failure probability referred to extreme displacement and the mean value of dissipated energy are assessed by using the introduced stochastic indices of seismic bridge protection efficiency. A parametric analysis for protective devices with different mechanical parameters is developed for a proper selection of parameters of isolation devices under different situations.     

Application of the predictable model of regional time-magnitude to North and Southwest China region

In this paper, the method which can combine different seismic data with the different precision and completeness, even the palaeo-earthquake data, has been applied to estimate the yearly seismic moment rate in the seismic region. Based on this, the predictable model of regional time-magnitude has been used in North China and Southwest China. The normal correlation between the time interval of the events and the magnitude of the last strong earthquake shows that the model is suitable. The value of the parameter c is less than the average value of 0.33 that is obtained from the events occurred in the plate boundary in the world. It is explained that the correlativity between the recurrence interval of the earthquake and the magnitude of the last strong event is not obvious. It is shown that the continental earthquakes in China are different from that occurred in the plate boundary and the recurrence model for the continental events are different from the one for the plate boundary events. Finally the seismic risk analysis based on this model for North China and Southwest China is given in this paper.     

Seismic Inventory Simulation and Conformance Test Based on the Monte Carlo Method——A Case Study of the Fenhe-Weihe Belt

Artificial earthquake catalogue simulation is one of the ways to effectively improve the incompleteness of the existing earthquake catalogue,the scarcity of large earthquake records and the improvement of seismological research.Based on the Poisson distribution model of seismic activity and the Gutenberg-Richter magnitude-frequency relationship, the Monte Carlo method which can describe the characteristics of the stochastic nature and the physical experiment process is used.This paper simulates the future seismic catalogues of the Fenhe-Weihe seismic belt of different durations and conducts statistical tests on them. The analysis shows that the simulation catalogue meets the set seismic activity parameters and meets the Poisson distribution hypothesis,which can obtain a better simulated earthquake catalogues that meets the seismic activity characteristics.According to the simulated earthquake catalogues,future earthquake trends in this region are analyzed to provide reference for seismic hazard analysis.     

Earthquake-induced landslide displacement attenuation models and application in probabilistic seismic landslide displacement analysis

A landslide displacement (DLL) attenuation model has been developed using spectral intensity and a ratio of critical acceleration coefficient to ground acceleration coefficient. In the development of the model,a New Zealand earthquake record data set with magnitudes ranging from 5.0 to 7.2 within a source distance of 175 km is used. The model can be used to carry out deterministic landslide displacement analysis,and readily extended to carry out probabilistic seismic landslide displacement analysis. DLL attenuation models have also been developed by using earthquake source terms,such as magnitude and source distance,that account for the effects of earthquake faulttype,source type,and site conditions. Sensitivity analyses show that the predicted DLL values from the new models are close to those from the Romeo model that was developed from an Italian earthquake record data set. The proposed models are also applied to an analysis of landslide displacements in the Wenchuan earthquake,and a comparison between the predicted and the observed results shows that the proposed models are reliable,and can be confidently used in mapping landslide potential.     

新疆全区和分区地壳速度模型的分析

In this paper, we firstly analyze the ＂3,400 travel time table＂ used for a long time in Xinjiang Seismological Network to obtain the velocity structure models in accord with the table by fitting. Then we fit the velocity of all seismic phases recorded in Xinjiang region in January 2009 ~ December 2013. Simulation analysis is done on the reliability and stability of the velocities, and a concept is proposed for building subarea crustal velocity models according to partitioning of seismic cluster regions. The crustal velocity model suitable for the Yutian area is fitted with the data of all phases of seismic events within a radius of 1 ° around the 2014 Yutian Ms7. 3 earthquake since January 2009, and the model is applied to the relocation of the Yutian Ms7. 3 earthquake and determination of focal depths of the earthquake sequence.     

Research Progress on the Problem of Fluid,Heat and Energy Distribution near the Earthquake Source Area

As the basic problems in seismology, fluid, heat and energy distribution near earthquake sources during earthquake generation have been the leading subjects of concern to seismologists. Currently, more and more research shows fluid around earthquake source areas, which plays an important role in the process of earthquake preparation and generation. However, there is considerable controversy over the source of fluid in the deep crust. As for the problem of heat around earthquake source areas, different models have been proposed to explain the stress heat flow paradox. Among them, the dynamic weakening model has been thought to be the key to solving the heat flow paradox issue. After large earthquakes, energy distribution is directly related to friction heat. It is of timely and important practical significance to immediately implement deep drilling in-site surveying to gain understanding of fluid, friction heat and energy distribution during earthquake generation. The latest international progress in fluid, heat and energy distribution research has been reviewed in this paper which will bring important inspiration for the understanding of earthquake preparation and occurrence.     

ETAS Model Analysis on the Chang Island Earthquake Swarm in Shandong Province,China

Influenced by the layout of seismic network and the location of earthquakes, earthquake catalogs are often incomplete; such incompleteness of earthquake catalogue directly affects the analysis of sequence activity characteristics. In this paper, the GPU-acceleration-based g template matching method is used to scan the continuous waveforms of Chang Island earthquake swarm in Shandong Province from February 9 to August 20, 2017. In total, 15,286 earthquakes events were detected, which was more than 6 times compared with those in network catalogue and thus reduced the magnitude of completeness from 1.0 to 0.5. Based on the intergrated catalogue of earthquakes, the characteristics of Chang Island earthquake swarm were then analyzed using the Epidemic Type Aftershock Sequences (ETAS) model. The stochastic components in the ETAS model are used as a proxy for possible earthquake triggered by external forces (fluids). The results show that the proportion of earthquakes triggered by external forces of Chang Island swarm increases gradually (from 31.9% to 63.5%) and then decreases. The latter stage of swarm development is mainly affected by the self-excitation of earthquakes,suggesting that the fluids play an important role in the development of the Chang Island swarm. However, the triggering intensity of fluids to microseismicity is divergent in different periods, which may be related to the process of fluid permeation.     

An elastic-plastic analysis of short-leg shear wall structures during earthquakes

Short-leg shear wall structures are a new form of building structure that combine the merits of both frame and shear wall structures. Its architectural features, structure bearing and engineering cost are reasonable. To analyze the elastic-plastic response of a short-leg shear wall structure during an earthquake, this study modified the multiple-vertical-rod element model of the shear wall, considered the shear lag effect and proposed a multiple-vertical-rod element coupling beam model with a new local stiffness domain. Based on the principle of minimum potential energy and the variational principle, the stiffness matrixes of a short-leg shear wall and a coupling beam are derived in this study. Furthermore, the bending shear correlation for the analysis of different parameters to describe the structure, such as the beam height to span ratio, short-leg shear wall height to thickness ratio, and steel ratio are introduced. The results show that the height to span ratio directly affects the structural integrity; and the short-leg shear wall height to thickness ratio should be limited to a range of approximately 6.0 to 7.0. The design of short-leg shear walls should be in accordance with the "strong wall and weak beam" principle.     

Load history-based model for prestressed concrete beam damage evaluation

The residual capability of a damaged structure to resist further load is essential in optimal seismic design and post-earthquake strengthening. An experimental study on the hysteretic characteristics of prestressed concrete frame beams under different loading histories was performed to explore the influence of load history on energy dissipation and failure characteristics of the member. Based on the test results, the failure of the beam is def ined, and the relationship between the failure moment under cyclic load and from the skeleton curve is formulated. Finally, based on displacement and energy dissipation, a model for prestressed concrete beam damage-failure evaluation is developed. In this model, the effect of deformation level, cumulative dissipated energy, and loading history on prestressed concrete beam damage–failure is incorporated, thus it is applicable to stochastic earthquake forces.     

随机性细胞自动机的地震模拟的动力学含义

结合随机的能量输入和确定的能量损耗，本文用随机性细胞自动机(CA)进行了地震事件的数字模拟，并对事件进行了能量分维和时间序列的多重分形分析。初步结果表明，大量事件的能量-频次的统计分布可能遵从最经典的Gutenberg—Richter关系．不同的初始能量分布和不同的能量传递准则都对模型的输出产生影响，b值与模型参数的设置密切相关，地震现象本质上的复杂性可能是随机性与确定性的统一体现。     

细胞自动机的多重分形特征和动力学根源

用大量弹簧滑块组成的模型可以模拟地震的复杂性,本文以细胞自动机(CA)为数学工具,结合地震学和岩石力学的结果,考虑了能量的输入和损耗,进行了地震事件的数字模拟。对模型中输出的"地震"事件进行了时间和空间的多分形分析,并对自组织临界(SOC)状态进行了讨论,进而得到事件至少在时间域里的分布呈现出层次结构,符合自相似特征。本文的CA模型属于确定性的混沌系统,而对于处在SOC状态下的大量事件的频度和大小的统计与G-R指数律很好地吻合。结果表明,虽然自组织(SO)可能是更准确的地震表征,但SOC仍然是研究地震现象的很好的模式。     

北京及邻区微震活动的初步分析

通过对北京遥测地震台网近年来记录到的北京及邻区地震的震中分布,地震活动频度及能量释放强度的分析,得到本区地震活动在时间分布上具有“聚堆性”。在年发震频度,地震强度和能释放方面均具有双峰值特征,并且具有较好的一致性和同步性,在空间分布上具有条带特征,且形成北东～南西和北西～南东的两条相互交汇的条带。又通过统计分析得到本区发震概率最大的时间段是每年的１０月前后,而地震主要发生在北西～南东带上。     

Parameter estimation of the stochastic AMR model and its application to the study of several strong earthquakes

Introduction According to many published papers, seismicity in time-space domain shows some characteristics, such as doughnut epicenter distribution (Mogi, 1969) or quiescence of seismic activity before large earthquakes (WANG, et al, 2002), and aftershock decay (Ogata, 1998). In recent years, more and more seismologists (Lynnr, Steven, 1990) have found that many strong earthquakes are preceded by enhancing regional seismicity and accelerating strain energy release (ZHANG, et al, 2001). T…     

Simulation of broadband seismic ground motions at dam canyons by using a deterministic numerical approach

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.     

Effect of travelling waves on stochastic seismic response and dynamic reliability of a long-span bridge on soft soil

It is generally known that the variability of earthquake ground motion is mainly in time and space. To investigate the impact of this variability on the seismic performance of a long-span flexible structure, we discuss the seismic dynamic responses of a real bridge subjected to stochastic seismic ground motion. We incorporate the effect of wave passage by means of the method of probability density evolution based on dynamic time-history analysis from the perspective of stochastic dynamics. First, we introduce the theory of probability density evolution and a category of stochastic seismic model. We then conduct a series of deterministic seismic dynamic analyses of the bridge to establish the probability density equation. Eventually, we obtain the probability information at the level of the probability density function of the seismic response by solving the probability-density evolution equation. The results show that the impact of travelling waves on a long-span structure is related to the characteristics of the earthquake ground motion and the structure, and that travelling waves increase the variability of the seismic response.     

Rainfall data simulation by hidden Markov model and discrete wavelet transformation

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.     

地震活动的随机标度和非线性标度律

把地震作为一个复杂系统，研究了地震活动的随机性质．当不考虑震级范围时，全球地震活动、人震的余震和区域震群均有以幂次律为特征的长尾现象．地震的强度由震级确定，具有一特定震级的地震可形成一个地震活动系列，很多这样的地震活动系列就形成具有各种震级的地震的集合．不同地震系列间的统计特征由随机标度来表征，随机标度表明了由地震震级分类的不同地震系列间统计时刻的标度关系．为了统一地方、区域和全球地震活动性的统计特性，引入了非线性标度率．