Prediction of near-field strong ground motions for scenario earthquakes on active fault

1 Introduction Earthquake disaster investigations show that numerous strong earthquakes were caused by remobilization of active faults. Major casualties and severe damage to buildings as well as signi?cant economic losses resulted from the ground motions of strongearthquakescausedbyactivefaultslocatedbeneath urban areas. Recently, the potential hazard prediction of and its mitigation against active faults located beneath urban areas have become an important research topic for seismologists and…     

The Influence of a Local Fault Zone on High Energy Tremor Occurrence During Longwall Mining of a Coal Seam

Underground mining of coal seams in the Upper Silesian Coal Basin in Poland is accompanied by seismic activity of varying magnitude. The investigations which have been performed for several years distinguished high energy mine tremors connected directly with mining or coupled with geological structures, such as large faults. In mined seams, local fault zones occur. Faults in these zones are usually small, with throws comparable with coal seams thicknesses. Local fault zone may be responsible for the occurrence of high energy tremors as well as large faults, as presented in this article. An analysis of source mechanism of high energy tremors generated during longwall mining of the coal seam No. 510, with presence of a local fault zone, in one of the Polish hard coal mines in the Upper Silesian Coal Basin was performed. For this purpose, the seismic moment tensor inversion method was used. In most of foci, the process of shear predominated. Determined nodal plane parameters were correlated with parameters of faults forming the local fault zone. High energy tremors were generated mostly by dislocations on faults of the local fault zone. Weakening of roof rocks in the neighborhood of local fault zone takes an important role too, and was responsible for share of implosion in the focal mechanism.     

Rating damage potential of ground motion records

In this study, a total of 115,246 ground motions recorded during earthquakes of Moment magnitudes ranging from M_w 5.0 to M_w 9.0 are analyzed statistically. A total of 21 ground motion parameters characterising the recorded acceleration time histories are used in the analysis. Classification of these parameters through statistical correlation is reported and a parameter called "distance from zero-amplitude axis," or d_Z-A, is formulated in the principal component space. The ability for d_Z-A to rate the damage potentials of strong motion records is evaluated through correlation of d_Z-A with Japan Meteorological Agency(JMA) instrumental seismic intensities. This parameter can be used to rate damage potential of any strong motion record irrespective of the magnitude and location of the earthquake. It can also be used in selecting ground motion records of appropriate damage potential in seismic design and probabilistic analysis.     

最不利设计地震动研究

实际记录到的真实地震动在工程结构的抗震研究、分析和设计中往往作为一种施加到结构上使结构振动，直至破坏的地震荷载．如何合理选择真实的地震动记录作为研究结构地震反应的输入，一直是国内外抗震研究和设计中引人关注的重要问题．本文首先提出了最不利设计地震动的概念；然后在收集到的国内外5000余条被认为有重要意义的地震动记录基础上，利用综合估计地震动潜在破坏势的方法，对４种场地类型分别给出了长周期、短周期和中周期结构的国内外最不利设计地震动；最后通过几类不同结构的地震反应分析，初步验证了本文所确定的最不利设计地震动的可靠性和合理性．      

Study on the severest real ground motion for seismic design and analysis

How to select the adequate real strong earthquake ground motion for seismic analysis and design of trucures is an essential problem in earthquake engineering research and practice.In the paper the concept of the severest design ground motion is proposed and a method is developed for comparing the severity of the recorded strong ground motions.By using this method the severest earthquake ground motions are selected out as seismic inputs to the structures to be designed from a database that consists of more than five thousand significant strong ground moton records collected over the world.The selected severest ground motions are very likely to be able to drive the structures to their critical response and thereby result in the highest damage potential.It is noted that for different structures with diffferent predominant natural periods and at different sites where structures are located the severest design ground motions are usually different.Finally.two examples are illustrated to demonstrate the rationality of the concept and the reliability of the selected design motion.     

随机方法在地震烈度速报中的应用

我国地震监测台网间距大,很难实现大震发生时地震烈度分布图的快速编制.基于随机方法,利用历史小震数据反演地震动估计模型的参数,参考地震发生时获取的少量强震动数据,选取合适的震源参数,正演地震动场的分布.根据地震烈度与地震动参数的经验关系,实现地震烈度速报.本方法可以模拟大震的近断层地震动特征,对高烈度区的判断较目前常用的烈度速报方法更为合理.研究成果既可以用于首张烈度分布图的发布,还能够用于地震烈度的动态修正.     

相对局部区域震源参数随机不确定性经验关系研究

在进行未来破坏性地震的强地面运动数值模拟时,震源参数选取的准确性对地震动预测的结果影响很大。震源参数的确定存在很多不确定性因素,既包含随机的不确定性因素,又包含认知的不确定性因素。本文在大量地震事件及文献调研的基础上,运用统计学方法对具备随机不确定性特征的震源参数进行统计研究,以震源参数经验公式的形态建立解释其随机性和不确定性的数学模型。为了研究局部地区震源参数的定标关系特征,获得更加适用于局部地震密集区域,尤其是包含中国大陆地区在内的局部区域的震源参数的经验关系,本文从GCMT地震目录中选取了1 700多个M_W≥5.5的地震事件,运用统计学方法研究地震密集地区的震源参数经验关系,包括震级、地震矩、破裂面积等,增加了相对较大的局部范围内凹凸体的地震样本数量,从统计学角度计算更加适合局部区域的震源参数的经验关系。统计结果表明:局部区域震例获得的震源参数的经验关系与不限区域震例获得的经验关系存在差异,尤其是涉及到断层破裂面积、凹凸体相关参数时差异较大,局部区域内震例获得的震源参数的经验关系将更具有代表性。应用本文获得的相对局部区域的经验公式计算未来破坏性地震的强地面运动所需的震源参数时,获得的地震动预测结果将更能体现目标区域真实的地震动特征,进而提高地震动预测结果的可靠性。      

Seismic design spectra and mapping procedures using hazard analysis based directly on oscillator response

The calculation of design spectra for building sites threatened by seismic ground motion is approached by considering the maximum responses of linearly elastic oscillators as indicators of ground motion intensity. Attenuation functions describing the distribution of response as a function of earthquake magnitude and distance are derived using 68 components of recorded ground motion as data. With a seismic hazard analysis for several hypothetical building sites, the distributions of maximum oscillator responses to earthquakes of random magnitude and location are calculated, and spectra are drawn to indicate the maximum responses associated with specified probability levels. These spectra are compared to design spectra calculated from published methods of amplifying peak ground motion parameters. The latter spectra are found to be inconsistent in terms of risk for building sites very close and very far from faults. A ground motion parameter defined to be proportional to the maximum response of a 1 Hz, 2 per cent damped linearly elastic oscillator is investigated; this parameter, in conjunction with peak ground acceleration, is found to lead to risk-consistent design spectra. Through these two parameters, a design earthquake magnitude and design hypocentral distance are defined, for a specified building site and risk level. The use of these parameters in the seismic hazard mapping of a region is illustrated.     

矿山地震研究述评

就采矿引起的诱发地震活动,即矿山地震的国际研究动态进行评述.重点介绍矿山地震的命名、早期观测与研究、几个主要矿震国家的情况、矿震的分类、矿震的震源机制、矿震震源参数与定标率等问题.还就利用矿山作为天然地震的预报实验场和作为地震技术的推广市场问题进行探讨.     

汉中地区农村房屋抗震性能调查分析研究

整理并分析汉中地区的地震背景、地震动参数和地质灾害,调查区域内地震动参数有差异的9类样本行政镇的931栋典型农村房屋,研究典型农村房屋的结构类型、抗震概念设计和建造场地等因素对房屋抗震性能的影响。结果表明:汉中地区地质构造复杂,深大断裂发育,94.7%的区域为灾害易发区,存在4个地震烈度异常区;农村既有房屋结构类型有土木结构、砖木结构、砖混结构和框架结构,其中砖木结构和砖混结构是主要的抗震结构类型,框架结构是新型抗震结构类型;区域内农村房屋的建造场地条件危险性大并且抗震概念设计不足,房屋震害严重,村民的工程地质和地震地质等相关知识匮乏。该研究可为村镇房屋的防震减灾工作提供参考。     

面向地震烈度仪的现地地震动预测模型的构建与验证

利用初期P波预警参数构建现地地震动预测模型,使其在达到设定阈值时快速发出报警信息,是现地地震预警系统面临的一个关键问题,直接关系到发布信息的准确性和及时性.针对地震烈度仪基于微机电系统传感器记录到的数据质量较差,通过两次积分获取的位移存在较大偏差,会引起更多的误报和漏报,本文采用不同阶数(1—4阶)的巴特沃斯滤波器,分...     

Recipe for Predicting Strong Ground Motion from Crustal Earthquake Scenarios

We developed a recipe for predicting strong ground motions based on a characterization of the source model for future crustal earthquakes. From recent developments of waveform inversion of strong motion data used to estimate the rupture process, we have inferred that strong ground motion is primarily related to the slip heterogeneity inside the source rather than average slip in the entire rupture area. Asperities are characterized as regions that have large slip relative to the average slip on the rupture area. The asperity areas, as well as the total rupture area, scale with seismic moment. We determined that the areas of strong motion generation approximately coincide with the asperity areas. Based on the scaling relationships, the deductive source model for the prediction of strong ground motions is characterized by three kinds of parameters: outer, inner, and extra fault parameters. The outer fault parameters are defined as entire rupture area and total seismic moment. The inner fault parameters are defined as slip heterogeneity inside the source, area of asperities, and stress drop on each asperity based on the multiple-asperity model. The pattern of rupture nucleation and termination are the extra fault parameters that are related to geomorphology of active faults. We have examined the validity of the earthquake sources constructed by our recipe by comparing simulated and observed ground motions from recent inland crustal earthquakes, such as the 1995 Kobe and 2005 Fukuoka earthquakes.     

基于砌体结构破坏损伤的地震烈度物理标准研究

为了研究基于砌体结构破坏的地震烈度物理标准,将15个地震动参数按属性(峰值、频率、持时和能量)分成4类,将地震记录按地震动三要素(峰值、频率、持时)分成3组,求出每组记录作用下砌体结构的延性系数,计算出各个参数值和延性系数的相关系数,比较分析这些相关系数发现地震动峰值加速度、有效峰值加速度、地震动输入能量和滞回耗能都能表征地震动对砌体的破坏势,并且这4个参数都和烈度有很好的相关性,可以作为烈度的物理标准。     

中国仪器地震烈度增量与场地放大系数的关系研究

相对于基岩的中国仪器地震烈度增量可以作为地震小区划的一个重要指标,也可以作为研究区建(构)筑物差异抗震设防的可靠依据。使用2021年2月13日福岛地震期间日本KiK-net台网120个台阵记录的地震动数据,根据18种地震动参数的定义和《中国地震烈度表》中中国仪器地震烈度的算法,分别计算了相对基岩的、土层上的中国仪器地震烈度增量和这些地震动参数的放大系数,然后用一元、二元回归分析方法分别建立它们之间的经验关系式。结果表明：(1)一元回归分析中,中国仪器地震烈度增量与持时超过0.3秒的加速度阈值(a_0.3)的放大系数的相关系数最高且为0.918,与峰值地面加速度(PGA)、水平向最大谱烈度(SI)的放大系数的相关系数均在0.870以上;(2)从中国规范的II类场地到III类场地(或美国规范的C类场地到E类场地),中国仪器地震烈度增量的均值逐渐增大;(3)相比于一元回归结果,二元回归分析中的中国仪器地震烈度增量与18种地震动参数放大系数两两组合的相关系数普遍有所提高,其中中国仪器地震烈度增量与PGA和SI放大系数组合的相关系数最高且为0.9261。     

Characteristics of mining tremors within the near-wave field zone

Mining in the Upper Silesian Coal Basin, Poland, induces tremors with magnitudes ranging up to 4.3. The recordings of mining tremors from the near-wave fiel and the far-wave field show different characteristics of ground motion.Knowledge of these characrteristics, has an enormous practical importance when solving the problems of resistance of underground workings against seismic impacts. The near-wave field is characterized by a domination of the high frequency components of motion, and the seismograms often are a single pulse Geomechanical interpretation of them leads to the conclusion that this pulse corresponds to a single exciting force. This fact is also reflected in the rockbursts: the potentially damaging ground motion which is restricted to the seismic source region.The seismometric data have shown that the peak particle velocities from a hypocentral distance of 200–300 m, resulted in more than 3 cm/s. The peak ground velocities appear to be dependent on stress drop , and peak particle velocities reaching 5 m/s may occur. The computational example proves that in a thick coal seam the pulse with the stress =1.8 MPa from the tremor at the short source distance can generate the rockburst.     

2D numerical simulations of earthquake ground motion: examples from the Marche Region,Italy

A detailed numerical simulation of the ground motion and a site response analysis for two towns in the Marche Region (Treia and Cagli) is carried out on the basis of structural models deduced from available geological and geophysical data. In both cases, the reference event is an M = 5.7 earthquake associated with a normal fault located beneath each town. The ground motion is computed using the 2D spectral element method (SPEM 2D). The method solves the propagation of the seismic field through complex geological structures and enables an estimate of the effects of deep crustal structure, superficial geology, and topography on ground motion. Numerical simulations of the seismic field are performed along 2D vertical planes containing the seismic source. Strong ground motion has not been yet recorded in the two towns; therefore, the numerical simulation of ground motion represents a way to overcome the lack of instrumental data. The simulations carried out for Treia show that ground motion is influenced by both source mechanism and effects due to propagation through the geological structure, while ground motion in Cagli features strong local effects, caused by the presence of alluvial deposits under a large area of the town.     

不同倾角断层对场地动力放大效应的分析

一般认为断层有一定的隔震作用,但是也有不少震害表明断层附近的破坏反而比较严重。为探讨其中机理,采用有限元方法分别建立包含不同倾角无厚度断层的场地模型,并分析了在各种频率入射波的作用下该场地的动力反应。计算结果表明,断层对场地的动力反应有一定的放大作用,特别是当入射波的频率与场地的基频接近时,放大效应更为明显。计算结果还表明,断层的倾角对场地的动力反应也有影响,随着断层倾角的减小,断层出露点附近的动力放大效应增大。     

Stochastic Finite Fault Modeling of Subduction Zone Earthquakes in Northeastern India

In this article, a stochastic finite fault source model is calibrated to estimate ground motion in northeastern India for intermediate depth events originating in the Indo-Burmese tectonic domain. A total of 47 three-component accelerograms from eight events with magnitudes ranging from M _w 4.8–6.4 are used to estimate the input source and site parameters of the finite fault source model. Key seismic parameters such as stress drop (Δσ) and site amplification function are determined from the recorded strong motion data. The obtained stress drop of the eight recorded events lies in between 105 and 165 bars.     

基于特大地震发生率的川滇地区地震危险性预测新模型

川滇地区是我国地震危险性较高的地区之一.本文基于对特大强震的风险性考虑,使用全球地震模型OpenQuake软件,建立了川滇地区地震危险性预测新模型.首先根据构造特征划分多个震源分区,并整理出这些震源分区内断层活动特征与滑动速率;基于震源分区和断层模型,使用GPS应变率转换成的锥形古登堡-里克特关系作为整个区域的地震积累率,并允许超过历史最大震级的特大地震的出现,结合活动断层滑动速率所积累的地震发生率,给出震源分区内断层地震源和背景地震源的地震发生率的比率分配关系;在活动断层分段上,保留了大型断裂或其主要部分,没有根据小的阶区来对断层进行详细分段,以便分配特大地震发生率;并使用地震率平滑方法分配背景地震发生率.最后在OpenQuake中加入地震动预测方程,计算出了川滇地区的PGA分布图,为区域地震危险性提供科学依据.