3-D physical model in strong ground motion numerical simulation： A case study of Kunming basin

Seismic hazard assessment based on urban active faults can provide scientific bases for city planning and projectconstruction,while numerical simulation of strong ground motion is an important method for seismic hazard pre-diction and assessment.A 3-D physical model in conformity with real strata configuration of(mainly)the Quater-nary is a prerequisite to ensure the reliability of the simulation results.In this paper,we give a detailed account ofthe technical scheme and process for creating a 3-D physical model in Kunming basin.The data used are synthe-sized from seismogeological data,borehole data,topographic data,digital elevation mode(DEM)data,seismicexploration results and wave velocity measurements.Stratigraphic division is based mainly on shear wave velocity,with strata sequence taken into consideration.The model construction is finally accomplished with ArcGIS andmany relevant programming techniques via layer-by-layer stacking(in depth direction)of the adjacent mediuminterfaces(meshes).Meanwhile,a database of 3-D physical models is set up,which provides model data and pa-rameters for strong ground motion simulation.Some processing methods and significant issues are also addressedin the paper in accordance with different types of exploration and experimental data.     

复合地震源模拟强地面运动-以1679年三河-平谷Memssub8.0地震为例

利用复合震源模型和人工合成地震图的算法, 以1679年三河——平谷Ms8.0地震为例,计算了北京地区的宽频带强地面运动. 其结果可为今后该地区的地震危险性评估和工程抗震提供一定的物理参数. 通过考察该地区的地质与地球物理区域背景, 利用计算机数值模拟的方法, 对北纬39.3deg;~41.1deg;东经115.35deg;~117.55deg;所围限的北京范围进行了设定地震的仿真模拟,并合成了强地面运动. 通过分析影响强地面运动的几个关键因素,给出了北京地区强地面运动峰值加速度和速度分布特征,比较了合成强地面运动记录与通过衰减关系计算所得的结果. 同时,还对复合震源模型的优点和局限性给出了充分的讨论. 利用数值模拟方法所得的较为真实的强地面运动参数,即加速度、速度、位移和时程特征,可为北京地区工程建设的抗震设计、救援设施的选址、以及金融及保险部门的风险性评估提供一定的依据.     

Strong motion simulation by the composite source modeling: A case study of 1679 <Emphasis Type="Italic">M</Emphasis>8.0 Sanhe-Pinggu earthquake

In this study, a composite source model has been used to calculate the realistic strong ground motions in Beijing area, caused by 1679 M _S8.0 earthquake in Sanhe-Pinggu. The results could provide us the useful physical parameters for the future seismic hazard analysis in this area. Considering the regional geological/geophysical background, we simulated the scenario earthquake with an associated ground motions in the area ranging from 39.3°N to 41.1°N in latitude and from 115.35°E to 117.55°E in longitude. Some of the key factors which could influence the characteristics of strong ground motion have been discussed, and the resultant peak ground acceleration (PGA) distribution and the peak ground velocity (PGV) distribution around Beijing area also have been made as well. A comparison of the simulated result with the results derived from the attenuation relation has been made, and a sufficient discussion about the advantages and disadvantages of composite source model also has been given in this study. The numerical results, such as the PGA, PGV, peak ground displacement (PGD), and the three-component time-histories developed for Beijing area, have a potential application in earthquake engineering field and building code design, especially for the evaluation of critical constructions, government decision making and the seismic hazard assessment by financial/insurance companies.     

Numerical simulation of strong ground motion for the M_s8.0 Wenchuan earthquake of 12 May 2008

The Wenchuan earthquake of 12 May 2008 is the most destructive earthquake in China in the past 30 years in terms of property damage and human losses. In order to understand the earthquake process and the geo-morphological factors affecting the seismic hazard, we simulated the strong ground mo-tion caused by the earthquake, incorporating three-dimensional (3D) earth structure, finite-fault rupture, and realistic surface topography. The simulated ground motions reveal that the fault rupture and basin structure control the overall pattern of the peak ground shaking. Large peak ground velocity (PGV) is distributed in two narrow areas: one with the largest PGV values is above the hanging wall of the fault and attributed to the locations of fault asperities and rupture directivity; the other is along the north-western margin of the Sichuan Basin and caused by both the directivity of fault rupture and the ampli-fication in the thick sediment basin. Rough topography above the rupture fault causes wave scattering, resulting in significantly larger peak ground motion on the apex of topographic relief than in the valley. Topography and scattering also reduce the wave energy in the forward direction of fault rupture but increase the PGV in other parts of the basin. These results suggest the need for a localized hazard as-sessment in places of rough topography that takes the topographic effects into account. Finally, had the earthquake started at the northeast end of the fault zone and ruptured to the southwest, Chengdu would have suffered a much stronger shaking than it experienced on 12 May, 2008.     

Ground motion attenuation of MS8.0 Wenchuan earthquake

The great M_S8.0 Wenchuan earthquake has been the most destructive earthquake since 1949 in China. The earthquake occurred no more than half a year after the establishment of the National Strong Motion Observation Network System (NSMONS) of China; what is more, the epicenter was located in the area with dense strong motion observation stations so that a large number of strong motion records of the main shock were obtained. In this paper, 501 strong motion records from 167 observation stations are utilized to establish the ground motion attenuation relations in three directions in the range of fault distance less than 600 km. The result shows the difference of seismic motion attenuation in two horizontal directions is insignificant. It is the first time that strong-motion records are used to establish the ground motion attenuation relations of the M_S8.0 earthquake in China.

     

1999年台湾集集大地震强地面运动的模拟

利用有限断层模型对1999年台湾集集大地震所产生的近场强地面运动进行了数值模拟,尝试了将具有明确物理意义的震源动力模型的研究结果应用于描述震源过程。计算结果显示,基岩台或接近工程基岩台的计算模拟记录同观测记录符合得很好。进一步研究表明,当综合考虑场地效应对地震动影响时,模拟计算结果得到了明显的改善,同实际观测记录更为相符。本文的研究结果说明,为了科学合理地预测大地震所产生的强地面运动,应综合考虑影响地震所产生的地面运动的"三要素",即:震源过程、传播路径及场地效应。     

1679年三河—平谷8级地震地表破裂端部特征及其地质意义

地震地表破裂端部的几何结构与运动学特征研究有助于科学认识断裂的破裂传播与终止过程.夏垫断裂是华北平原区最为重要的隐伏强震构造之一,于1679年发生了三河—平谷M8历史大地震,但其同震地表破裂长度及端部变形特征仍存争议.基于前人研究结果,在野外地质调查的基础上,跨1679年三河—平谷8级地震地表破裂端部布设了 2条浅层地...     

汶川地震强地面运动模拟

基于确定性震源模型的方法主要用于计算低频(11 Hz)地震动常用经验格林函数法或随机方法,对低频地震动模拟不够准确．本文在确定性震源模型方法基础上,尝试采用分解给定的震源模型的方法来模拟宽频带(0.1——10 Hz)强地面运动,即采用分级离散断层面和分解断层面破裂单元上升时间的方法,增加震源时间函数中的高频信号,从而避免了对地震记录丰富程度和准确性的依赖．文中模拟计算了汶川MS8.0地震在8个地震观测台的地震动,将模拟结果和观测记录进行了加速度时程曲线和傅里叶振幅谱的对比分析．对比结果显示,模拟估计的地震动峰值加速度和持续时间与观测记录的数据基本在plusmn;50%的精度范围内相同,傅里叶振幅谱显示模拟结果有得到10 Hz左右的高频成分. 四川盆地中的台站模拟结果高频衰减比观测记录要快,原因是模拟过程没有考虑场地效应.对强地震动模拟还是要综合考虑震源、传播路径和场地的影响．研究结果表明,此改变震源输入的确定性方法可应用于模拟近断层宽频强地面运动．      

Near‐source seismic demand and pulse‐like records: A discussion for L'Aquila earthquake

Rupture directivity effects in ground motion are known since many years to both seismologists and earthquake engineers, i.e. in sites that are in a particular geometrical configuration with respect to the rupture, the velocity fault‐normal signals may show a large pulse which occurs at the beginning of the record and contains the most of energy. The results are waveforms different from ordinary ground motions recorded in the far field or in geometrical conditions not favorable with respect to directivity. Current attenuation laws are not able to capture such effect well, if at all, and current probabilistic seismic hazard analysis is not able to predict the resulting peculiar spectral shape. Moreover, it is believed that structures with dynamic behavior in a range of periods related to the pulse period may be subjected to underestimated seismic demand. In the paper this is investigated and increments in both elastic and inelastic seismic actions are quantified using a large dataset of records, from the next generation attenuation project (NGA), in which a fraction is comprised of velocity pulses identified in other studies. These analyses employ recently developed tools and procedures to assess directivity effects and to quantify the associated threat in terms of seismic action on structures. Subsequently, the same tools are used in one of the first attempts to identify near‐source effects in the data recorded during a normal faulting earthquake, the mainshock of the recent Abruzzo (central Italy) sequence, leading to conclude that pulse‐like effects are likely to have occurred in the event, that is (1) observation of pulse‐like records in some near‐source stations is in fair agreement with existing predictive models, (2) the increment in seismic demand shown by pulse‐like ground motion components complies with the results of the analysis of the NGA data, and (3) seismic demand in non‐impulsive recordings is generally similar to what expected for ordinary records. The results may be useful as a benchmark for inclusion of near‐source effect in design values of seismic action and structural risk analysis. Copyright © 2010 John Wiley & Sons, Ltd.     

GP断层破裂模型在青海门源MS6.9地震强地面运动模拟的适用性研究

2022年1月8日青海省门源县发生M_S6.9地震,震中附近遭受了强烈地震破坏.为验证Graves和Pitarka开发的GP断层破裂模型在震前对中国地区地震动场的预测与评估能力,本文基于GP法,考虑不同上升时间系数（rc）的影响,对门源地震进行了确定性地震动模拟.将模拟结果在地震动衰减规律、波形与幅值和烈度分布三个方面分别与青藏地区的地震动峰值预测方程、强震观测记录和根据强震记录自动产出的烈度图进行了对比.结果表明,当rc为9.0时,模拟记录与实测记录和地震动峰值预测方程基本一致.本文较好的重现了门源地震的强震动场,在合理选取rc的情况下,GP法可以应用于中国地区震前强地震动场的预测和估计.

     

基于余震序列的地震烈度快速评估方法研究——以青海门源6.9级地震为例

地震烈度快速评估产品是破坏性地震发生后应急工作"黑箱期"内研判灾情的重要依据.文章基于青海门源6.9级地震震后2 h内的余震序列,采用最短断层距地震动衰减模型快速评估地震烈度.研究结果显示:利用震后30分钟内的余震序列得到的烈度分布可以初步判定重灾区及灾区范围,但灾区范围略小于实际调查结果;利用1.5 h内的余震序列得...