Abstract: An M4.9 earthquake occurred at the junction of Gaoyou and Baoying on July 20, 2012. In this paper, 43 sets of strong motion records of the main shock are analyzed. With these data, we analyzed the characteristics of the peak ground motion value, attenuation relation, duration and acceleration response spectrum. We draw the peak acceleration contour map of the region near the epicenter. The contour line is smooth and the trend of long axis is northwest-southeast. Distribution of peak acceleration of the observed records is basically consistent with the real intensity distribution. Compared with the predicted result based on the seismic attenuation relation proposed by Yu Yanxiang and Wang Suyunon for eastern China and the Fifth-generation ground motion zonation map, the horizontal PGA and PGV of Gaoyou-Baoying earthquake are higher than the predicted results that are based on the model of Fifth-generation ground motion zonation map, while the PGV is similar with the predicted results which are based on Yu Yanxiang and Wang Suyun's model. We regressively analyzed the spatial-temporal change curves of the two types of relative ground motion durations. Compared with the predicted results proposed by Bommer et al. (2009) based on the NGA strong motion records, the durations of all the three components of this earthquake are higher. 10 typical recordings' acceleration response spectra with 5% damping are calculated, their peak periods are around 0.1~0.3s. The acceleration response spectrum of the station 32BYT, which has the largest amplitude, is considerably larger than the Chinese code design spectra, while it becomes notably smaller when the period is larger than 0.4s. Compared with the horizontal bedrock acceleration response spectrum predicted by the attenuation relationship for the eastern part of China, the observed response spectrum shape is similar with the predicted ones, while almost all the observed response spectrum values (except station 32YCT)are smaller than the predicted bedrock acceleration response spectrum. These phenomena suggest that this earthquake has a weak impact on the seismic fortification standards in this area. Using H/V single-station spectral ratio method, amplitude and site amplification effect of the two typical stations are calculated, and the results show the H/V values are obviously larger than that of ground microtremor. This suggests that the site of the station has obvious amplification effect on ground motion.

Key words: Gaoyou-Baoying earthquake, amplitude, duration, response spectrum, site effect

摘要： 2012年7月20日江苏高邮、宝应交界处发生4.9级地震。文中利用江苏省强震动台网获取的43组主震强震动记录，从地震动峰值特征、衰减关系、持时和加速度反应谱等方面进行分析，结果表明：观测记录的峰值加速度等值线长轴沿SW-NE方向展布，与真实的烈度等值线格局基本一致；水平向峰值加速度值与中国东部地区地震动衰减关系预测值基本相符，水平向峰值加速度值和水平向峰值速度值均高于第五代区划图（GB18306-2015）中使用的衰减关系预测值；回归分析了2种地震动相对持时的空间变化曲线，与基于NGA强震记录库的全球经验预测曲线相比，此次地震动持时高于预测值；加速度反应谱峰值周期在0.1～0.3s之间，与相应地区基于中国东部地区水平向基岩加速度反应谱衰减关系计算得到的基岩反应谱的形状和峰值周期相比，几个典型加速度记录的反应谱峰值周期相对较小，但反应谱形状大致相似；采用H/V单台谱比法分析了2个典型台站在地震中的场地放大效应，结果表明台站场地对地震动存在明显的放大现象。

关键词: 高邮-宝应地震, 幅值, 反应谱, 持时, 场地效应