ACTIVE FAULTING IN NORTH VIETNAM: INSIGHTS FROM MORPHOTECTONIC AND GEODETIC STUDIES ALONG THE RED RIVER AND DIEN BIEN PHU FAULT ZONES

Abstract

Tue Red River (RRF) and Dien Bien Phu (DBP) faults are very important strike-slip faults in SE Asia. The RRF marks the boundary between the South China and Indochina blocks which was shaped in two phases: during sinistra! ductile shear active in 27-16 Ma, followed by exhumation and uplift from a depth of 20-25 km, and as dextral, predominantly brittle shear active in Plio-Quatemary times. The amount of post-Miocene dextral offset has been variously reconstructed at 20 to 57 km, whereas the size of individua! offset of Quatemary valleys has been calculated as 9 m to nearly 2 km. [...]