基于动力学拐角频率的汶川主震近场地震动随机合成
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摘要
对汶川Ms8.0级地震主震近场范围地震动进行模拟。模拟采用基于动力学拐角频率的有限断层地震动随机合成方法,即,每个子源的震源谱拐角频率与该子源被触发时已破裂的子源总数相关,同时借助一个能量守恒标度因子弥补动力学拐角频率可能引起的高频地震动幅值水平的低估。震源采用加州理工大学构造观测组CTO反演的有限断层模型。借助加速度反应谱及反应谱比的计算,将模拟得到的52个近场强震观测台站处的地震动,与国家地震台网数据中心提供的主震观测记录进行对比。最后基于对断层附近面积为387.2km×195.2km区域内地震动的模拟,将模拟地震动的峰值加速度分布图与震后调查得到的水平峰值加速度分布图进行分区对比。
Ground motions from the Great Wenchuan earthquake were simulated by using the stochastic finite-fault modelling method based on dynamic corner frequency.In the method,the corner frequency in the source spectrum for each subsource is related to the number of the subfaults ruptured by the time the subsource is triggered,and a scaling factor was using to compensate the diminishing of the high-frequency spectral level from using dynamic corner frequency.The finite-fault source model obtained from the inversion of the far-field records,presented on the website of Caltech Tectonics Observatory,was employed.Ground motions at 52 near-field stations were simulated and compared with the observed motions in terms of 5% damped response spectrum and the average spectral ratio.Ground motions in a rectangle near-fault region on the surface with an area of 387.2 km by 195.2 km were also simulated.The peak accelerations of the simulated ground motions were mapped and compared with the PGA contour mapped based on observation data.Based on the comparison,the effects of the far-field data based source model on the simulated ground motion were discussed.
Ground motions from the Great Wenchuan earthquake were simulated by using the stochastic finite-fault modelling method based on dynamic corner frequency.In the method,the corner frequency in the source spectrum for each subsource is related to the number of the subfaults ruptured by the time the subsource is triggered,and a scaling factor was using to compensate the diminishing of the high-frequency spectral level from using dynamic corner frequency.The finite-fault source model obtained from the inversion of the far-field records,presented on the website of Caltech Tectonics Observatory,was employed.Ground motions at 52 near-field stations were simulated and compared with the observed motions in terms of 5% damped response spectrum and the average spectral ratio.Ground motions in a rectangle near-fault region on the surface with an area of 387.2 km by 195.2 km were also simulated.The peak accelerations of the simulated ground motions were mapped and compared with the PGA contour mapped based on observation data.Based on the comparison,the effects of the far-field data based source model on the simulated ground motion were discussed.
引文
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[2]于海英,王栋,杨永强,等.汶川8.0级地震强震动特征初步分析[J].震灾防御技术,2008,3(4):321-336(YuHaiying,Wang Dong,Yang Yongqiang,et al.Thepreliminary analysis of strong ground motion characteristicsfrom the Ms 8.0 Wenchuan Earthquake,China[J].Technology for Earthquake Disaster Prevention,2008,3(4):321-336(in Chinese))
[3]Boore D M.Simulation of ground motion using thestochastic method[J].Pure and Applied Geophysics,2003,160(3-4):635-676
[4]Beresnev I A,Atkinson G M.Stochastic finite-faultmodeling of ground motions from the 1994 Northridge,California,earthquake I.Validation on rock sites[J].Bulletin of the Seismological Society of America,1998,88(6):1392-1401
[5]Motazedian D,Atkinson G M.Stochastic finite-faultmodeling based on a dynamic corner frequency[J].Bulletin of the Seismological Society of America,2005,95(3):995-1010
[6]Sladen A.(2008).Preliminary Result:05/12/2008(Mw7.9),East Sichuan[DB/OL].http://www.tectonics.caltech.edu/slip_history/2008_e_sichuan/e_sichuan.html.
[7]Atkinson G M,Boore D M.Ground-motion relations foreastern north America[J].Bulletin of the SeismologicalSociety of America,1995,85(1):17-30
[8]华卫,陈章立,郑斯华.2008年汶川8.0级地震序列震源参数分段特征的研究[J].地球物理学报,2009,52(2):365-371(Hua Wei,Chen Zhangli,Zheng Sihua.Astudy on segmentation characteristics of aftershock sourceparameters of Wenchuan M8.0 earthquake in 2008[J].Chinese Journal of Geophysics,2009,52(2):365-371(inChinese))
[9]Boore D M,Joyner W B.Site amplifications for genericrock sites[J].Bulletin of the Seismological Society ofAmerica,1997,87(2):327-341
[10]Bassin C,Laske G,Masters G.The current limits ofresolution for surface wave tomography in north America[J].EOS Trans AGU.1998,81:F897
[11]程万正,陈学忠,乔慧珍.四川地震辐射能量和视应力的研究[J].地球物理学进展,2006,21(3):692-699(Cheng Wanzheng,Chen Xuezhong,Qiao Huizhen.Research on the radiated energy and apparent strain of theearthquakes in Sichuan province[J].Progress inGeophysics,2006,21(3):692-699(in Chinese))
[12]阮祥.川滇中小地震震源参数的研究[D].兰州:中国地震局兰州地震研究所,2007(Ruan Xiang.Research offocal parameter of medium and small earthquakes inYunnan and Sichuan[D].Lanzhou:Lanzhou Institute ofSeismology,China Earthquake Administration,2007(inChinese))
[13]Ghasemi H,Fukushima Y,Koketsu K,et al.Ground-motion simulation for the 2008 Wenchuan,China,earthquake using the stochastic finite-fault method[J].Bulletin of the Seismological Society of America,2010,100(58):2476-2490
[14]徐锡伟,张培震,闻学泽,等.川西及其邻近地区活动构造基本特征与强震复发模型[J].地震地质,2005,27(3):446-461(Xu Xiwei,Zhang Peizhen,Wen Xueze,etal.Features of active tectonics and recurrence behaviors ofstrong earthquakes in the western Sichuan province and itsadjacent regions[J].Seismology and Geology,2005,27(3):446-461(in Chinese))
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