宁夏及邻区地震震源衰减模型及震源参数研究
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摘要
选取2003年1月至2011年12月宁夏及邻区发生的201个ML2.0以上地震事件进行反演,用经验格林函数计算得到本区地震震源谱衰减模型。在已知非弹性衰减系数和场地响应的条件下,计算得到震源谱并研究了近震震级与拐角频率、地震矩、震源破裂半径及应力降之间的关系。详细分析了震源参数误差大小及各种误差影响因素。对剩余应力降时空演化特征分析研究结果表明:高剩余应力降集中分布在宁夏北部宁蒙交界地区、低剩余应力降分布在宁夏中部同心、中卫一带,银川盆地中南部的吴灵地区和宁夏南部海原断裂带中东段剩余应力降变化较为明显,在时间分布上这两个区域剩余应力降在中强地震前均有降低—增强的趋势。
201 events of ML≥2.0 are selected from January 2003 to December 2011 in Ningxia and its adjacent areas for inversion.Seismic spectral attenuation models are calculated by empirical Green function.On the base of known inelastic attenuation coefficient and site response,the source spectra are calculated and the relationship between local magnitude and corner frequency,seismic moments,rupture radius and stress drop are studied.Magnitude of error of seismic source parameters and influence factors are analyzed in detail.Temporal evolution characteristics of residual stress drop analysis results show that high residual stress drop is concentrated in the northern Ningxia and Inner Mongolia border region,low in Tongxin and Zhongwei area of central Ningxia.Residual stress drop changes more obviously in the Wuling area of south-central Yinchuan basin and middle-east Haiyuan fault of southern Ningxia.On these two regions,residual stress drops have decrease-enhancement trend in temporal distribution before strong earthquakes.
201 events of ML≥2.0 are selected from January 2003 to December 2011 in Ningxia and its adjacent areas for inversion.Seismic spectral attenuation models are calculated by empirical Green function.On the base of known inelastic attenuation coefficient and site response,the source spectra are calculated and the relationship between local magnitude and corner frequency,seismic moments,rupture radius and stress drop are studied.Magnitude of error of seismic source parameters and influence factors are analyzed in detail.Temporal evolution characteristics of residual stress drop analysis results show that high residual stress drop is concentrated in the northern Ningxia and Inner Mongolia border region,low in Tongxin and Zhongwei area of central Ningxia.Residual stress drop changes more obviously in the Wuling area of south-central Yinchuan basin and middle-east Haiyuan fault of southern Ningxia.On these two regions,residual stress drops have decrease-enhancement trend in temporal distribution before strong earthquakes.
引文
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[11]Brune J N.Tectonic Stress and the Spectra of Seismic Shear Waves from Earthquakes[J].J GeophysRes,1970,75(26):4 997-5 009.
[12]Shearer P M.Introduction to Seismology[M].Cambridge Press,1999.
[13]Savage J C.Relation of corner frequency to fault dimensions[J].J Geophys Res,1972,77(20):3 788-3 795.
[2]Shearer P M,Prieto G A,Hauksson E.Comprehensive analysis of earthquake source spectra insouthern California[J].J Geophys Res,2006,111,B06303,doi:10.1029/2005JB003979.
[3]Allmann B P,Shearer P M.Spatial and temporal stress drop variations in small earthquakes nearParkfield,California[J].J Geophys Res,2007,112,B06305,doi:10.1029/2006JB004395.
[4]赵翠萍,陈章立,华卫,等.中国大陆主要地震活动区中小地震震源参数研究[J].地球物理学报,2011,54(6):1 478-1 489.
[5]杨明芝,马禾青,廖玉华.宁夏地震活动与研究[M].北京:地震出版社,2007.11-46.
[6]师海阔,朱新运,贺永忠,等.宁夏及邻区地震震源参数研究[J].大地测量与地球动力,2010,30增刊(1):38-43.
[7]许英才,许文俊,李鸿庭,等.利用数字地震波资料研究宁夏地区介质非弹性衰减和场地响应[J].大地测量与地球动力,2011,30增刊(1):33-37.
[8]金春华.宁夏及邻区和祁连山中东段的S波非弹性衰减Q值研究[J].内陆地震,2009,23(1):18-25.
[9]金春华,赵卫明,盛菊琴,等.利用宁夏大峰矿特大爆破资料研究地震波的衰减特性[J].地震地磁观测与研究,2009,30(2):46-48.
[10]金春华,李鸿庭,盛菊琴.宁夏及邻区地震动衰减和场地响应的分区研究[J].地震地磁观测与研究,2012年第5/6期合刊.
[11]Brune J N.Tectonic Stress and the Spectra of Seismic Shear Waves from Earthquakes[J].J GeophysRes,1970,75(26):4 997-5 009.
[12]Shearer P M.Introduction to Seismology[M].Cambridge Press,1999.
[13]Savage J C.Relation of corner frequency to fault dimensions[J].J Geophys Res,1972,77(20):3 788-3 795.
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