Characteristics of earthquake source and ground motions in Northern Vietnam investigated through the 2020 Moc Chau M5.0 earthquake sequence

On July 27, 2020, a shallow earthquake with a moment magnitude (M_w) of 5.0 occurred near Moc Chau in Northwestern Vietnam. Several shallow aftershocks, clustered in a small area, followed the mainshock. The mainshock caused damage to infrastructure in the source area, and considerable shaking was felt in many high buildings in surrounding cities. This event was the first recorded significant earthquake by a newly operational Vietnam broadband seismic network. The ground motions of this earthquake sequence were adequately recorded by this network. The strike-slip rupture mechanisms of the events were evaluated through moment tensor inversion analysis. After this earthquake, a field survey was conducted. A combined analysis of damage patterns and source mechanisms revealed that this earthquake sequence might be associated with the active right-lateral Da River fault. The site classification of each station that recorded data on the Moc Chau series was evaluated by computing the horizontal-to-vertical spectral ratio. This earthquake sequence was analyzed to evaluate the characteristics of the earthquake source and the seismic wave propagation in Northwestern Vietnam and to address the potential earthquake engineering applications of this information.