The town of Haenam in southwest Korea lies partially on reclaimed coastal land and experienced an unprecedented earthquake swarm during April and May 2020. Construction of a new town in the area means that there is demand to evaluate the seismic hazard caused by site-specific amplification of seismic ground motions by artificial unconsolidated cover. We used a microtremor horizontal-to-vertical spectral ratio (HVSR) method to identify resonance frequencies, image depths to bedrock, and assess seismic ground vulnerability across the epicentral area of the recent earthquake swarm. Microtremor measurements were taken at 144 sites across an 18.5 km × 12.5 km study area. The HVSR analysis shows resonance frequencies as low as 1.1 Hz. Using mean shear-wave velocities obtained by Multi-Channel Analyses of Surface Waves (MASW), we find that resonance frequencies correspond to depths to bedrock of between 3 m and 56 m. There are clear relationships between the distribution of resonance frequencies, depths to bedrock, surface geology, and areas of development in recent land reclamation projects. Higher resonance frequencies characterize areas of thin sedimentary cover or hard rock sites, while relatively low resonance frequencies characterize reclaimed land or greater depths to bedrock. We quantify the seismic hazard potential across the study area using the seismic vulnerability of ground index (K_g), and observe a clear association between zones of high K_g and areas of reclaimed land. This study demonstrates the value of the HVSR technique in characterizing the subsurface and assessing seismic vulnerability in areas of reclaimed land, where it can be used as a viable and low-cost alternative to large-scale active seismic refraction or MASW measurements. The results can also be used to inform and guide urban planning projects.

韩国西南部的海南（Haenam）镇部分位于开垦的沿海土地上，并在2020年4月和2020年5月经历了前所未有的地震。人工非固结覆盖层的地震地震动。我们使用了微震水平与垂直光谱之比（HVSR）方法来识别共振频率，到基岩的图像深度，并评估最近地震群震中区域的地震地面脆弱性。在18.5 km×12.5 km研究区域的144个地点进行了微震测量。HVSR分析显示共振频率低至1.1 Hz。使用通过表面波多通道分析（MASW）获得的平均剪切波速度，我们发现共振频率对应于3 m至56 m之间的基岩深度。在最近的土地开垦项目中，共振频率的分布，基岩的深度，地表地质与开发区域之间存在明显的关系。较高的共振频率表征薄的沉积覆盖层或坚硬的岩石区域，而相对较低的共振频率表征开垦的土地或基岩的更大深度。我们使用地面指数的地震脆弱性来量化整个研究区域的潜在地震危险（较高的共振频率代表着薄薄的沉积覆盖层或硬岩场地的区域，而较低的共振频率代表了开垦土地或基岩的更大深度。我们使用地面指数的地震脆弱性来量化整个研究区域的潜在地震危险（较高的共振频率表征薄的沉积覆盖层或坚硬的岩石区域，而相对较低的共振频率表征开垦的土地或基岩的更大深度。我们使用地面指数的地震脆弱性来量化整个研究区域的潜在地震危险（K _g），并观察到高K _g区域与开垦土地区域之间的明确联系。这项研究证明了HVSR技术在表征填海土地的地下特征和评估地震脆弱性方面的价值，该技术可以用作大规模主动地震折射或MASW测量的可行且低成本的替代方法。结果还可以用于指导和指导城市规划项目。