鲁甸地震强震动记录与地震动衰减模型的对比研究

利用2014年鲁甸M_S6.5地震断层距小于300 km的32个自由场地观测台站的地震动加速度记录，分析了地震动峰值加速度(PGA)和峰值速度(PGV)的空间分布特征，并对已有地震动衰减模型中的NGA-West2四个模型和1个中国川藏区模型进行了比较分析.研究表明，地震动PGA和PGV衰减最快的方向与断层主破裂方向一致.在整个断层距(R_rup)范围内大多数台站的地震动PGA、PGV和加速度反应谱值(Sa(T=0.1、5.0 s))均位于NGA-West2四个模型预测曲线的±1倍标准差之外.PGA、PGV和Sa(T=5.0 s)的事件内残差均值在-1.43~-0.74之间.Sa(T=0.01~5.0 s)事件内残差均值在整个距离范围内均表现出系统性偏负.NGA-West2四个模型的PGA事件内残差的空间分布特征相似，其最大正值和最大负值分布区域的震源-场地方位角约为-90°和90°，与主破裂断层方向垂直，所处地势较为平坦且台站场地V_S30相对较大.NGA-West2四个模型总体上会较大地高估鲁甸地震整个断层距范围内各个周期尤其是短周期(T < 1.0 s)的地震动加速度反应谱值.考虑本地区实际地震资料的中国川藏区地震动衰减模型也会在一定程度上高估鲁甸地震大多数台站的地震动加速度反应谱值，但是相对于NGA-West2四个模型，其预测值更接近鲁甸地震的实际观测值.

Comparison of strong ground motion records from Ludian,China, earthquake with ground-motion attenuation models

A total of 32 free-field accelerograms recorded at rupture distances of less than 300 km during Ludian M_S6.5 earthquake in 2014 were used to analysis the spatial distribution of peak ground acceleration (PGA) and peak ground velocity (PGV), and compare the Ludian earthquake ground motions with the four NGA-West2 and one China Sichuan-Tibet area ground motion attenuation models. The results show that, the fastest attenuation direction of PGA and PGV is consistent with the main fault rupture direction. For most Ludian station recordings within the entire rupture distances, the PGA, PGV and spectral acceleration (Sa(T=0.1, 5.0 s)) are beyond ±1 standard deviation of the prediction curves of the four NGA-West2 models. The average intra-event residuals of the PGA, PGV and Sa(T=5.0 s) ranged from -1.43 to -0.74. The average intra-event residuals of Sa(T=0.01~5.0 s) showed a systematic negative within the entire rupture distances. The spatial contours of intra-event residuals for PGA predicted by the four NGA-West2 models are almost the same, and the regions of maximum positive and maximum negative intra-event residuals are mainly distributed with the source-to-site azimuth approximating to -90° and 90°, which are perpendicular to the main fault rupture direction. The terrain of these two areas is relatively flat, and the station sites V_S30 in these areas are relatively large. As a whole, four NGA-West2 models will significantly overestimate the spectral acceleration within the entire rupture distances from the Ludian earthquake, especially in short period (T<1.0 s). The China Sichuan-Tibet area ground-motion model considering the actual seismic data in this area will also overestimate the spectral acceleration of the Ludian earthquake to a certain extent, but compared with the four NGA-West2 models, its predicted values will be closer to the actual observed values.