The southern East African Rift System (EARS) is an early-stage continental rift with a deep seismogenic zone. It is associated with a low-to-moderate seismic hazard, but due to its short and sparse instrumental record, there is a lack of ground-motion studies in the region. Instead, seismic hazard assessments have commonly relied on a combination of active crustal and stable continental ground-motion models (GMMs) from other regions without accounting for the unusual geological setting of this region and evaluating their suitability. Here, we use a newly compiled southern EARS ground-motion database to compare six active crustal GMMs and four stable continental GMMs. We find that the active crustal GMMs tend to underestimate the ground-motion intensities observed, while the stable continental GMMs overestimate them. This is particularly pronounced in the high-frequency intensity measures (>5 Hz). We also use the referenced empirical approach and develop a new region-specific GMM for southern EARS. Both the ranked GMMs and our new GMM result in large residual variabilities, highlighting the need for local geotechnical information to better constrain site conditions.

中文翻译：

---

非洲东南部地面运动模型的排名和开发

东非裂谷系统（EARS）南部是一个早期大陆裂谷，具有深层地震带。它与低到中度地震危险有关，但由于仪器记录短而稀疏，该地区缺乏地面运动研究。相反，地震危险性评估通常依赖于其他地区的活动地壳和稳定大陆地面运动模型（GMM）的组合，而没有考虑该地区不寻常的地质环境并评估其适用性。在这里，我们使用新编译的南部 EARS 地面运动数据库来比较六个活动地壳 GMM 和四个稳定的大陆 GMM。我们发现，活动的地壳 GMM 倾向于低估观测到的地面运动强度，而稳定的大陆 GMM 则高估了它们。这在高频强度测量（>5 Hz）中尤其明显。我们还使用参考的经验方法，为南部 EARS 开发了一个新的区域特定 GMM。排名后的 GMM 和我们的新 GMM 都会产生较大的残差变异，这凸显了对当地岩土信息的需求，以更好地限制场地条件。