ACTIVE CHARACTERISTICS OF SAM NUA FAULT ZONE DURING NEOTECTONIC STAGE

Abstract

The Sam Nua fault zone lies in the Sop Cop fault zone (in the NW of Vietnam). In Laos, the Sam Nua fault zone composed of two fault branches, which are the main branch called Na Vine - Nam and Tham Pong - Na Ham fault. The first part of fault zone is NW-SE directed extension while the southeastern end turns gradually to latitude direction and sloping NW. In the present - day tectonic period, it has been undergone two stages of motion: right lateral slips in the Miocen - Pliocen time and left lateral slip in the latter phase (Pliocen - Quatylity). The amplitude of horizontal movement is estimated approximately 1200m at a slip - rate of 4mm/year and the vertical is 50m. Recently, this fault zone has been reactivated with a magnitude 5.5 Richter by earthquake recorded. This study will attribute to reveal the process of displacement in Sop Cop fault zone.