汶川8.0级地震陕西省数字强震动记录分析

Analysis of Digital Strong Motion Records of the M8.0 Wenchuan Earthquake from the Network of Shaanxi Province

本文对2008年5月12日四川汶川8.0级地震陕西数字强震动台网27个台的地震加速度记录进行了处理和分析,包括对加速度波形数据的基线调整、滤波、加速度反应谱计算,以及速度和位移计算。结果表明:除局部场地条件的影响外,大地震的能量辐射方向和传播路径中介质的横向不均匀对PGA_H衰减的离散性可能有一些影响;对于同一烈度值,PGA/PGV较小,PGA在数值上平均只有PGV的5倍左右,反映了地震动的低频成分比较丰富;绝大部分强震台所处地区的烈度为Ⅴ—Ⅶ度;PGA_H与水平单分向加速度峰值PGA_(E-W)和PGA_(N-S)中较大值之间的相对偏差绝大部分小于10%;波形的性质为面波,盆地中覆盖土层较厚的场地长周期的面波更为发育,波列持续时间较长;局部场地的介质特性对地震动特征有相当大的影响,盆地中较厚的覆盖土层对较长周期的地震波有明显的放大作用。

Records of 27 stations from Shaanxi Digital Strong Motion Network from the May 12th, 2008 M8.0 Wenchuan earthquake are processed and analyzed, including baseline correction, filtering of acceleration traces, computing acceleration response spectrum, velocities and displacements. The result shows that both direction energy radiation of the large earthquake and horizontal inhomogeneous medium along the wave traveling path might have some effect on scattering degree of the attenuation of PGAH, besides influence of local site conditions. For same intensity, the ratios of PGA/PGV are commonly smaller, averagely about 5 times, which indicates that long period components are rich in ground motions. Intensities for most sites where stations are located are within Ⅴ-Ⅶ. The larger one among PGAE-W and PGAN-S is commonly quite close to related PGAH, less than 10% in relative deviation. The waves are mainly surface waves, so that the thicker the sediment is, the longer the shaking lasts. Local site conditions have relatively large effects on ground motions. The thick sediments can in basin can significantly amplify long-period their components.