Abstract

In the framework of this paper the authors have carried out the study of the Induce Earthquake Occurrence in the last time in Sông Tranh 2 reservoir. The obtained results have shown that:

1/ The earthquakes occurred in the last time located in the Sông Tranh 2 reservoir are the induce earthquake ones. The earthquake epicenters distributed along the Trà My - Trà Bồng sub-latitudinal fault zone (280⁰-300⁰). The maximum earthquake could be occurs in the reservoir probably reach to magnitude 5.7 to 6.1. The coefficient b of the Gutenberg - Richter law has the value b= 0.8317, more than b of the natural earthquake of the Sông Tranh 2 region (b= 0,604). The frequency of the earthquake occurrence with the magnitude from 4.5 to 6.0 is the following: M= 4.5 is 11 months; M= 5.0 (29 months); M= 5.5 (76 months); and M= 6.0 (198 months).

2/ The earthquake occurred at 13 hour 41 minute 28 second (GMT), M_S= 4.6, I₀= 6.0 (MSK-64), 22 October, 2012 has the epicenter located at the center of the reservoir, 5.5 km far from the dam in the west. The focus mechanism:  depth of the hypocenter is about 4.5 km; the length of the fault plane is 1.8 km with the direction 285⁰, normal right strike slip; dip angle 75⁰; direction of the stress field is 320⁰.