Spatial variation of the active stress field in the North West of Vietnam: implication for related geohazard mitigation

Abstract

The NW of Vietnam is currently affected by a stress field characterizing by approximately NS and EW sub-horizontal maximum and minimum principal stress axis respective1y. The results obtained from field investigations and numeric modelisation reveal that the present stress field varies not only in relative magnitude but also in orientation of principal stress axes from point to point and in depth. The tectonic stress variation strong1y depends on the geometry and active kinematics of faults as well as on their earthquake history. The modeling shows that the tectonic stress field tends to simplity from the subsurface downward to 40km depth. At this level depth, the stress concentrates a1ong the Dien Bien-Lai Chau fault while other faults release stress. Horizontally, the high tectonic stress accumulates in some area such as western side of the Dien Bien-Lai Chau fault, the area from Dien Bien Dong to Lai Chau, a1ong the Son La, Song Ma faults and in some segments of Song Ca fault. These stress anomalies link close1y to historic earthquakes.