攀枝花台近震震级测算研究

通过对攀枝花台近震震级测算和周边地震台网及台站的震级结果进行综合对比,包括对测算方法和地震波形传播方式进行探讨.试图研究台站近震震级测算差异并初步找出与地质构造的相关关系;以期提高台站近震震级测算能力,减小误差.     

北京台网震相分析与大震速报

阐述了北京台网近远震和特殊震例的震相分析以及如何迅速准确地对大震进行速报。     

Considering potential seismic sources in earthquake hazard assessment for Northern Iran

Located on the Alpine-Himalayan earthquake belt, Iran is one of the seismically active regions of the world. Northern Iran, south of Caspian Basin, a hazardous subduction zone, is a densely populated and developing area of the country. Historical and instrumental documented seismicity indicates the occurrence of severe earthquakes leading to many deaths and large losses in the region. With growth of seismological and tectonic data, updated seismic hazard assessment is a worthwhile issue in emergency management programs and long-term developing plans in urban and rural areas of this region. In the present study, being armed with up-to-date information required for seismic hazard assessment including geological data and active tectonic setting for thorough investigation of the active and potential seismogenic sources, and historical and instrumental events for compiling the earthquake catalogue, probabilistic seismic hazard assessment is carried out for the region using three recent ground motion prediction equations. The logic tree method is utilized to capture epistemic uncertainty of the seismic hazard assessment in delineation of the seismic sources and selection of attenuation relations. The results are compared to a recent practice in code-prescribed seismic hazard of the region and are discussed in detail to explore their variation in each branch of logic tree approach. Also, seismic hazard maps of peak ground acceleration in rock site for 475- and 2,475-year return periods are provided for the region.     

Regional variation of spectral parameters for seismic design from broadband probabilistic seismic hazard analysis

The characterisation of the seismic hazard input is a critical element of any seismic design code, not only in terms of the absolute levels of ground motion considered but also of the shape of the design spectrum. In the case of Europe, future revisions of the seismic design provisions, both at a national and a pan‐European level, may implement considerable modifications to the existing provisions in light of recent seismic hazard models, such as the 2013 European Seismic Hazard Model. Constraint of the shape of the long‐period design spectrum from seismic hazard estimates on such a scale has not been possible, however, owing to the limited spectral period range of existing ground motion models. Building upon recent developments in ground motion modelling, the 2013 European Seismic Hazard Model is adapted here with a new ground motion logic tree to provide a broadband Probabilistic Seismic Hazard Analysis for rock sites across a spectral period range from 0.05 seconds to 10.0 seconds. The resulting uniform hazard spectra (UHS) are compared against existing results for European and broadband Probabilistic Seismic Hazard Analysis and against a proposed formulation of a generalised design spectrum in which controlling parameters can be optimised to best fit the uniform hazard spectra in order to demonstrate their variability on a European scale. Significant variations in the controlling parameters of the design spectrum are seen both across and within stable and active regions. These trends can help guide recalibrations of the code spectra in future revisions to seismic design codes, particularly for the longer‐period displacement spectrum.     

"霍山地震窗"小震序列运动学参数时变特征研究

利用安徽及邻近地区的数字化地震资料,详细研究了“霍山地震窗口”小震序列的构造环境背景应力和视应力变化特征。结果表明,环境应力值和视应力值不仅能反映震“源”区的应力背景强弱,在距未来强震震中比较远的特殊构造部位,即素有“地震活动穴位”的地震窗口的小地震,同样能较客观反映出孕震区附近应力环境的信息,在华东中强地震前后应力状态的差异性是显著的。     

渐近式地震速报和地震信息服务的工作程序设想

本文讨论了渐近式地震速报和地震信息服务的工作程序的设想。随着通讯技术和数字地震观测技术的发展,地震速报工作已经开始逼近地震参数快速测定的地震学极限,即地震波传播速度的有限性和震相分析的复杂性带来的极限,从而使同时提高速度和精度存在档大的困难,中国方面,防震减灾工作以地震快速反应的要求却不一定是速度与精度的同时提高,而 分阶段的、依距地震发生的时间而不同的,这就使得渐近式的地震速报程序成为可能。从更     

Stochastic model of bedrock earthquake motion and determination of its parameters

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Migration of earthquake foci in Europe

Summary The present paper deals with the migration of earthquake foci in the horizontal and vertical plane observed in Europe and Asia Minor in the period 1901–69.     

On the observability of isotropic seismic sources: The July 31, 1970 Colombian earthquake

Theoretical calculations are made to study the observability of isotropic components of seismic sources. In particular we consider the 1970 deep Colombian earthquake, for which a precursory isotropic component was previously reported by Gilbert and Dziewonski.We compare an ultra-long period vertical record at Pasadena of the 1970 event to synthetic seismograms calculated both for Gilbert and Dziewonski's source model and for the pure double-couple source of Furumoto and Fukao, and obtain better overall agreement for the latter. The amplitude of the long-period synthetic for the isotropic source is about 5–15 times smaller than the synthetic for the deviatoric source, suggesting that the data may be relatively insensitive to the presence of a small isotropic source. When this possibility was tested, the overall agreement was found to be almost completely insensitive to the presence of even a reasonably large isotropic component.However, the isotropic source was derived from multi-station moment tensor inversion, rather than from single-station studies. A numerical experiment on the effect of lateral heterogeneity of eigenfrequencies and of Q on the inversion for the moment tensor shows that even relatively small amounts of heterogeneity can produce spurious isotropic sources from moment tensor inversion.     

海南区域地震与爆破震源参数特征

收集2008年以来海南测震台网记录的M_L 2.5以上地震及爆破资料,利用Brune圆盘模型,计算得出震源参数,发现地震、爆破的震源参数特征为:地震的拐角频率绝大多数大于爆破;地震应力降大于1,爆破应力降小于1;地震震源尺度绝大多数小于爆破。对一个有感疑爆事件,利用其拐角频率、应力降、震源尺度等参数,判定该事件为天然地震,与前人研究结果一致。由此可见,利用震源参数在地震速报、日常分析中判定事件类型具有实际意义。     

辽宁岫岩地震序列地震运动学参数时变特征的研究

利用辽宁数字地震台网1999年8月至2000年12月的数字地震资料, 详细研究了岫岩地震序列(1999年11月至2000年1月)前后直达S波的最大加速度峰值的时间变化特征, 及其与构造环境背景应力和视应力变化的一致性, 得到了地震运动学参数在前-主-余震形成和发生的演化过程中明显的差异性变化。 为探索前震的判别和强余震的预测, 提供了可快速精确测定的物理参数和掌握地震构造应力背景变化的物理信息。 通过对单台视应力、 剪应力τ₀值、 S波加速度峰值时间变化过程的对比分析表明, 这3个参量都是强烈地依赖于应力背景强弱的的物理量, 因此反映的是一种的物理过程, 具有一致的物理意义, 其时间变化过程具有很好的一致性。 这3种方法由于其计算过程简便, 在地震分布变化很小, 台站位置相对固定的条件下可较为精确的测定, 其异常的幅度明显高于正常背景值, 因此有较为显著的异常分辨率。 使用者可根据具体观测条件和现场研究的需要, 选取合适的研究方法。     

可用于台站地震速报的全自动计算软件

地震速报计算机联网技术系统 (FDEnet)已经在全国的大震速报台投入运行。该系统的应用 ,减少了数据传递过程中的话音传送环节 ,提高了数据传输速度和准确性。但该系统是将已经处理完成的数据输入、传输 ,不是直接用地震分析得到的原始数据进行处理 ,所以 ,存在人工输入分析处理     

Interrelation between seismicity parameters and delimiting potential seismic sources in a seismic statistical region and its influence on seismic risk estimation

In the paper, we have discovered the abnormal area distribution features of maximum variation values of ground motion parameter uncertainty with different probabilities of exceedance in 50 years within the range of 100°～120°E,29°～42°N for the purpose to solve the problem that abnormal areas of maximum variation values of ground motion parameter uncertainties emerge in a certain cities and towns caused by seismicity parameter uncertainty in a seismic statistical region in an inhomogeneous distribution model that considers tempo-spatial nonuniformity of seismic activity. And we have also approached the interrelation between the risk estimation uncertainty of a site caused by seismicity parameter uncertainty in a seismic statistical region and the delimitation of potential sources, as well as the reasons for forming abnormal areas. The results from the research indicate that the seismicity parameter uncertainty has unequal influence on the uncertainty of risk estimation at each site in a statistical region in the inhomogeneous distribution model, which relates to the scheme for delimiting potential sources. Abnormal areas of maximum variation values of ground motion parameter uncertainty often emerge in the potential sources of Mu≥8 (Mu is upper limit of a potential source) and their vicinity. However, this kind of influence is equal in the homogeneous distribution model. The uncertainty of risk estimation of each site depends on its seat. Generally speaking, the sites located in the middle part of a statistical region are only related to the seismicity parameter uncertainty of the region, while the sites situated in or near the juncture of two or three statistical regions might be subject to the synthetic influences of seismicity parameter uncertainties of several statistical regions.     

成都数字遥测地震台网的地震参数测定

对数字地震台用不同处理方法所给出的地震基本参数进行了对比，同时还对数字地震台网测定的地震参数与模拟地震台网测定的地震参数进行了对比。     

Statistical determination of significant curved I-girder bridge seismic response parameters

Curved steel bridges are commonly used at interchanges in transportation networks and more of these structures continue to be designed and built in the United States. Though the use of these bridges continues to increase in locations that experience high seismicity, the effects of curvature and other parameters on their seismic behaviors have been neglected in current risk assessment tools. These tools can evaluate the seismic vulnerability of a transportation network using fragility curves. One critical component of fragility curve development for curved steel bridges is the completion of sensitivity analyses that help identify influential parameters related to their seismic response. In this study, an accessible inventory of existing curved steel girder bridges located primarily in the Mid-Atlantic United States (MAUS) was used to establish statistical characteristics used as inputs for a seismic sensitivity study. Critical seismic response quantities were captured using 3D nonlinear finite element models. Influential parameters from these quantities were identified using statistical tools that incorporate experimental Plackett-Burman Design (PBD), which included Pareto optimal plots and prediction profiler techniques. The findings revealed that the potential variation in the influential parameters included number of spans, radius of curvature, maximum span length, girder spacing, and cross-frame spacing. These parameters showed varying levels of influence on the critical bridge response.     

Estimation of earthquake parameters in the Alborz seismic zone,Iran using generalized inversion method

Generalized inversion of the S-wave amplitude spectra from the strong-motion network data in the Alborz, Iran has been used to estimate simultaneously source parameters, site response and S-wave attenuation (Qs). To obtain an optimum inverse solution, and also for decreasing the uncertainty level, a frequency-dependent site amplification as a constraint, was imposed to five reference site responses. This constraint removes the undetermined degree of freedom in the inversion. Furthermore, for removing the trade-off between geometrical spreading and anelastic attenuation, a geometrical spreading factor was adopted from the Motazedian [20] study. A point source model has been calibrated against the resulting source terms and consequently source parameters, like corner frequency, moment magnitude and high frequency fall off coefficient, for each event has been determined separately. Also, based on the available data and their connectivity two sub-regions including western and eastern parts of Alborz located east and west of 52.5°E have been considered to see that if there is any possible systematic difference in their seismic source characteristics. The average stress drops obtained are about 182 and 116 bars, respectively for eastern and western Alborz. Another result of the study is the site responses, which have been determined for all of 81 stations individually. Though soil nonlinearity was detected at the Ab-bar station (experienced strong ground shaking, i.e., PGA>0.5 g) near to the epicenter of Manjil M7.4 earthquake of June 20, 1990, but an analysis of residuals showed generally a weak influence of soil nonlinearity (i.e., dependence of amplification on shaking level); probably because of the relatively weak levels of acceleration in our database. Finally, the shear wave quality factor (i.e., Qs) has been determined as a function of frequency represented by a linear equation in logarithmic scale. To evaluate the outcomes of the current study, the results have been compared with similar studies wherever it was available. The results of the current study are of utmost importance for seismic hazard assessment of the metropolitan area of Tehran, where 15 million people live, one-fifth of the population of Iran.     

The relation of earthquake foci to faults and the most recent movements of Southern Asia

This study presents an analysis of the interrelations between 700 earthquake foci (with M = 6–8 and M > 8) for the period from 1900 to 1980 and fault tectonics and neotectonic deformations in the territory of new folded belts and platforms in Southern Asia rejuvenated in the Cenozoic.The study shows that the seismic activity of ancient faults, that were tectonically passive in the Cenozoic, is nearly the same as that of the Cenozoic counterparts.Besides, it is established that the majority of earthquake foci are related to uplift regions, in which amounts of neotectonic deformation reach intermediate and minimum values, rather than to regions of maximum crustal deformations.     

设计地震动参数确定中的场地影响考虑

讨论了场地条件对场地设计地震动参数的影响问题,对国际上一些国家的抗震设计规范考虑该问题的相关规定作了介绍和分析,探讨了抗震设计对该问题处理的发展趋势,基于相关的强震纪录统计分析和场地模型计算反应分析已有的结果,研究了场地条件对场地设计地震动参数的影响特点和规律,重点考虑了场地类别和场地土体非线性的影响。结果这些分析与探讨结果,建议了用于不同类别场地设计地震动参数确定的一组经验系统。     

The influence of one-dimensional velocity sections on determining the key parameters of the earthquake sources in Azerbaijan

The paper addresses the construction of one-dimensional (1D) velocity models in the seismogenic regions of Azerbaijan taken individually and the analysis of implications of these models for estimating the key parameters of earthquake sources in Azerbaijan. We considered and analyzed the seismological data from the local earthquakes, the arrival times of the P-, P-g, Pn-, S-, Sg-, and Sn-waves recorded by the network of telemetry stations during the period from 2005 to 2014 with ml ≥ 2.5. For constructing the models, we used the VELEST program which calculates 1D velocity models from travel times of seismic waves. As a result, the 1D models were built for ten regions of Azerbaijan; the key parameters of the hypocenters of the earthquakes were recalculated; and the corrections to the body-wave arrival times at the observation stations were obtained, which increased the accuracy of locating the hypocenter of earthquakes.     

一种基于贝叶斯理论的P波双参数地震预警方法

为了及时、准确、可靠地发出地震预警信息,本文提出了一种基于贝叶斯理论的地震P波双参数预警方法.选取中国地震台网中心记录的四川地区的355条地震数据,统计P波触发后前3 s的P波平均周期τc和位移幅值Pd,结合贝叶斯理论建立震级和峰值加速度的预测模型,并以震级M4.5和峰值加速度为120 cm/s2为预警阈值,建立了地震...