Expression of triggered earthquakes at some hydropower plant reservoirs in Vietnam

Abstract

In this paper, the authors present the expression of triggered earthquakes at some hydropower plant reservoirs in Vietnam. The research results indicated that: - The triggered earthquakes with M > 4.0 have occurred at the Hoa Binh, Song Tranh 2 and Son La hydropower plant reservoirs. These reservoirs all have more than 100 m depth and locate on gneiss, granite or limestone rock backgrounds. - Triggered earthquakes at the Hoa Binh, Song Tranh 2 and Son La hydropower plant reservoirs are the rapid ones. The earthquake frequency has close ties with the water level change. - Vp/Vs ratio can be used as the main factor determining the triggered earthquake source. The natural earthquake sources linking with the reservoir and having the Vp/Vs ratio of 1.63-1.69 have the highest risk of triggered earthquake occurrence. - There is no risk of triggered earthquake occurrence at Hoa Binh hydropower plant’s reservoirany. Triggered earthquakes in the Song Tranh 2 reservoir continue occurring with the magnitude of smaller than 4.7. In the Son La reservoir, triggered earthquakes continue occurring in the coming time with the magnitude of more than 4.3 and may reach a maximum of 5.0.