2020年云南省巧家县MS5.0地震强震动记录初步分析

Strong motion record analysis of the Qiaojia MS5.0 earthquake in Yunnan Province, 2020

2020年5月18日云南省巧家县发生MS5.0地震,中国数字强震动台网的13个强震台站和昭通简易烈度计示范项目建设的43个烈度计台站,共接收168条强震动记录,经常规处理,绘制震区加速度峰值等值线图,并与云南地区常用地震动衰减关系进行对比,分析加速度峰值较大的几个台站频谱特性,计算地震动能量持时,讨论中小地震中高加速度峰值/低震害现象的成因,得到以下结论:①PGA等值线图形状较为平滑,其长轴呈NW—SE向展布;②云南地区常用地震动衰减关系预测值总体衰减趋势与观测值一致,但在近场(0—30 km)时,预测值基本偏小;③加速度峰值较大的几个台站记录主频集中在1—5 Hz;④小河镇台记录的能量持时较短,说明能量衰减较快,属脉冲型记录,不会对建筑物造成较大破坏。

An MS 5.0 earthquake occurred in Qiaojia County of Yunnan Province on May 18, 2020. 13 strong-motion stations of the China Digital Strong Motion Network and 43 intensity stations built in the Simple Intensity Demonstration Project of Zhaotong collected 165 sets of records in the earthquake mainshock. First, the strong-motion records were preliminarily processed and the PGA contour lines were drawn. Then the commonly used attenuation relation of strong motion in Yunnan was compared with the observed data and the spectral characteristics of several stations with large peak accelerations were analyzed, the ground motion energy durations were calculated. Based on these analyses we get some conclusions: ① The contour lines of PGA are smooth and their long axis spreads in the direction of northwest-southeast. ② The commonly used attenuation relationship of strong motion in Yunnan is consistent with observed data in general but smaller in the near field(0-30 km). ③ The peak frequency of records at stations with large peak accelerations is concentrated in 1-5 Hz. ④ The ground motion energy duration of the record at Xiaohe station is very short, indicating the energy decay is fast, so it will not cause great damage to buildings.