基于四区域椭圆模型的汶川8.0地震加速度峰值衰减关系拟合
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摘要
利用加速度记录直接拟合衰减关系时,现行几乎所有文献都采用圆模型,以震中距或震源距为观测点坐标位置的唯一统计量。对于长断层的大震而言,等震线的圆模型假设和实际等震线图存在严重的偏差,加速度峰值在沿断层方向的长轴和垂直于断层方向的短轴衰减关系差异非常明显。提出的加速度衰减关系的四区域椭圆模型,按断层破裂方向的长轴和过断层为中心垂直于长轴的短轴将地震记录观测点位置分为四个区域,以烈度等值线为参考,给出了四个区域内各自的加速度峰值等值线的椭圆近似曲线。并在此基础上得出了汶川8.0级地震加速度峰值在两个长半轴和两个短半轴方向上的衰减关系,和圆模型相比,该模型在精度上更加可靠,且能够反映断层破裂方向效应和上下盘效应,具有较强的工程应用价值。
At present,an equal-distance circle model is generally used for directly fitting acceleration peak attenuation curve,epicentral distance or focal distance is only the coordinate statistical parameter for a seismic observation station.For large earthquake with a long fault,the isoseismic curves of the equal-distance circle model exist serious deviation from realistic isoseismic curves.There is enormous differences between the acceleration peak attenuation curve along the long axis and that along the short axis.An four-area elliptical model was proposed here dividing seismic observation stations into four areas according to the long axis and the short axis.Every elliptical acceleration isoseismic curve in four areas was respectively figured out using interpolation in relation to seismic intensity isoseismic curves.On this basis,Wenchuan earthquake acceleration peak attenuation curve was derived along two long semiaxes and two short semiaxes.Comparing Wenchuan 8.0 rank earthquake acceleration peak attenuation curve using the four-area elliptical model with that using the circle model,the former was more close to the real situation and it could reflect the hanging and foot wall effect of fault and the direction effect of earthquake.
At present,an equal-distance circle model is generally used for directly fitting acceleration peak attenuation curve,epicentral distance or focal distance is only the coordinate statistical parameter for a seismic observation station.For large earthquake with a long fault,the isoseismic curves of the equal-distance circle model exist serious deviation from realistic isoseismic curves.There is enormous differences between the acceleration peak attenuation curve along the long axis and that along the short axis.An four-area elliptical model was proposed here dividing seismic observation stations into four areas according to the long axis and the short axis.Every elliptical acceleration isoseismic curve in four areas was respectively figured out using interpolation in relation to seismic intensity isoseismic curves.On this basis,Wenchuan earthquake acceleration peak attenuation curve was derived along two long semiaxes and two short semiaxes.Comparing Wenchuan 8.0 rank earthquake acceleration peak attenuation curve using the four-area elliptical model with that using the circle model,the former was more close to the real situation and it could reflect the hanging and foot wall effect of fault and the direction effect of earthquake.
引文
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[2]陶夏新.孙晓丹.陶正如.对新一代地震动衰减关系研究看法[C].第七届全国地震工程学术会议论文集,2006:58-65.
[3]地震工程与工程振动编辑委员会[M].汶川8.0级地震工程震害概览,科学出版社,2008,10:15-20.
[4]卢荣俭.地面运动峰值与烈度的相关关系[R].工程力学研究所报.79-011号,1979:20-40.
[5]Laubenbacher R,Pengelley D.Mathematical Expeditions[M].New York:Springer-Verlag Inc,1999:62-78.
[6]中国地震局震害防御司[M].汶川8.0级地震未校正加速度记录.地震出版社,2008.9:22-92.
[7]黄慧华.近源地震动峰值加速度衰减关系影响因素分析[J].工程地质学报,1998.6(1):61-66.
[8]姜慧.新疆地震烈度的椭圆衰减关系研究[J].高原地震,1993.15(4):90-96.
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