The Gyeongju area covers the intersection of two major young structural features in Korea: the Yangsan and Ulsanfaults. More than 60 Quaternary fault sites have recently been reported along these fault zones, which are thus considered major active tectonic features in southeast Korea. An earthquake of local magnitude ML = 5.8 struck the Gyeongju area on September 12, 2016; the largest instrumental earthquake recorded in South Korea. We performed detailed investigation for severely damaged buildings and houses in villages around the epicenter, and determined the characteristics and controlling factors of the earthquake damage. The distribution of damaged buildings is relatively scattered around the epicenter, which may be related to the relatively deep focal depth of approximately 13–15 km. The radius of the reported damage area affected by ground motion is approximately 17 km from the epicenter, which is almost equal to the focal depth. Old buildings with traditional styles are more seriously damaged than modern buildings, suggesting that the damage intensity depends on the building structure, material properties, and seismic design. Interestingly, in a small village, the degree of building damage is clearly divided by a small stream. Based on an electrical resistivity survey for the local geological condition, we found that the degree of building damages also strongly depends on the local unconsolidated alluvium thickness. Moreover, the orientation of tilted or damaged buildings is closely related to the general trend of the related faults indicating the propagation direction of ground motion. Although focal depth, building style, and foundation condition are the main controlling factors to the building damages caused during the 2016 Gyeongju earthquake, other minor factors could also be involved. This information will be useful to design proper construction codes for reinforced buildings and for hazard studies against future earthquakes in potential earthquake prone areas.

中文翻译：

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朝鲜东南部2016年ML = 5.8庆州地震的地震破坏及相关因素

庆州地区涵盖了韩国的两个主要年轻建筑特征：梁山和蔚山断层。最近在这些断层带上报告了60多个第四纪断层，这些断层被认为是韩国东南部的主要活动构造特征。2016年9月12日，庆州地区发生了ML = 5.8级地方地震；韩国有史以来最大的器乐性地震。我们对震中周围村庄严重受损的房屋和建筑物进行了详细调查，确定了地震破坏的特征和控制因素。震中周围受损建筑物的分布相对分散，这可能与大约13-15 km的相对较深的焦深有关。所报告的受地震动影响的损坏区域的半径距离震中约17公里，几乎等于焦深。传统风格的老建筑比现代建筑受到的破坏更严重，这表明破坏的强度取决于建筑结构，材料特性和抗震设计。有趣的是，在一个小村庄中，房屋损坏的程度明显除以一条小溪。根据当地地质条件的电阻率调查，我们发现建筑物破坏的程度也强烈取决于当地未固结的冲积层厚度。此外，倾斜或损坏的建筑物的方向与指示地面运动传播方向的相关断层的总体趋势密切相关。虽然焦深，建筑风格，基础条件是影响2016年庆州地震的建筑物损坏的主要控制因素，其他较小的因素也可能涉及。这些信息对于设计适当的加固建筑施工规范以及潜在地震多发地区对未来地震的危害研究非常有用。