Abstract

We consider the September 21, 2020, M_w = 5.5 seismic event, which occurred in the eastern part of the Tunka rift basin system and was followed by a relatively strong mb = 4.6 aftershock. The earthquake epicenter is localized within the Bystraya basin in the zone of prolonged seismic quiescence and is possibly confined to the Main Sayan fault zone. The hypocentral depth, according to the solution of the Baikal Branch, United Geophysical Survey, Russian Academy of Sciences (UGS RAS), is estimated as h = 18 km. The focal mechanisms of the main shock and strong aftershock are characterized by almost pure strike-slip movements, which agrees well with modern ideas about the tectonics of the area. The maximum shaking intensity observed in the populated areas closest to the epicenter is estimated at VI–VII on the MSK-64 scale. A shaking intensity of V and IV was observed in populated areas at distances over 180 and 500 km, respectively. This earthquake made it possible to obtain new data on the dynamic ground motion parameters. The maximum peak ground acceleration (PGA) of 187 cm/s² was recorded at the Talaya seismic station, which is the highest value for the territory of the Southern Baikal Region during the digital period of earthquake detection.

中文翻译：

---

2020年9月21日，M w = 5.5，贝加尔湖南部地区的Bystraya地震：仪器和宏观地震观测的初步结果

摘要

我们认为2020年9月21日的M _w  = 5.5地震事件发生在通卡裂谷盆地系统的东部，随后发生了相对较强的mb  = 4.6余震。地震震中位于局部Bystraya盆地内的长时间地震静止带中，并且可能仅限于主要的萨彦断裂带。根据俄罗斯科学院联合地球物理调查局贝加尔分校的解决方案，震中深度估计为h = 18公里。主震和强烈余震的震源机制以几乎纯的走滑运动为特征，这与该地区构造学的现代思想非常吻合。在MSK-64尺度上，在最靠近震中的人口稠密地区观察到的最大震动强度估计为VI-VII。在人口超过180 km和500 km的区域，分别观察到V和IV的晃动强度。这次地震使获得有关动态地面运动参数的新数据成为可能。塔拉亚地震台站记录的最大峰值地面加速度（PGA）为187 cm / s ²，这是在数字地震探测期间贝加尔湖南部地区的最高值。