On the southwestern Korean Peninsula, a 74-earthquake swarm was recorded between April 26 and May 9, 2020, with a maximum local magnitude (M_L) of 3.1. This is the third such event since instrumental seismic recordings began in South Korea in 1978. Because this area is located on a stable continent, this rare swarm event provides an opportunity to analyze earthquake sources and attenuation characteristics in this region. In this study, we first analyzed the intensity measure (IM) and the frequency content of the ground motions recorded during this swarm event. Next, we investigated the effects of earthquake magnitude and source-to-site distance on IMs, compared with those derived from international and local ground-motion models (GMMs). We found that the magnitude scaling slope (i.e., variation of IMs depending on M_L) of the earthquake swarm records for M_L ≥ 1.8 is similar to the slopes derived from GMMs, while for M_L < 1.8, the slope from the records is steeper. For distance scaling (i.e., variation of IMs depending on source-to-site distance), the slopes from records are gentler than those from GMMs. This indicates that ground motion attenuates slowly in this region, compared to other global regions.

在朝鲜半岛西南部，到2020年4月26日至5月9日记录了74次地震，最大局部震级（_ML）的3.1。这是自1978年在韩国开始仪器地震记录以来的第三次此类事件。由于该地区位于稳定的大陆上，因此这一罕见的群体事件为分析该地区的地震源和衰减特征提供了机会。在这项研究中，我们首先分析了该群体事件期间记录的地面运动的强度测量（IM）和频率内容。接下来，我们比较了地震烈度和震源到震源距离对IM的影响，并与国际和本地地面运动模型（GMM）得出的影响进行了比较。我们发现，大小缩放斜率（即，取决于M IM的变化_大号）的对M的震群记录_大号≥1.8类似于从转基因微生物产生的山坡上，而对于M_L <1.8，记录的斜率更陡。对于距离缩放（即，IM取决于源到站点距离的变化），记录的斜率比GMM的斜率平缓。这表明与其他整体区域相比，该区域的地震动衰减缓慢。