Response Of Channel Offsets To Dextral-slip Movement Of The Red River Fault Zone

The Red River fault (RRF), is one of the largest strike-slip faults from eastern Tibet. Its strike-slip movement plays an important controlling role for the red river tributaries development form. A large number of system streams respond to displacement by strike-slip faults as its right-lateral strike-slip movement in landscape. Different stages have different offset stream characteristics. Based on GoogleEarth、 ALOS images and ASTER GDEMS and field observations, we carefully extract active fault traces, stream channels as well as their offsets along the Red River Fault Zone, including the Vietnamese portion. We first focus on small-scale deflected gullies, and investigate the recent activity locations and characteristics. Then we examine the channels without river capture. Based on geomorphic analyses, the average-slip rates of late-Quaternary along the fault are constrained, which ranging from0.2mm/a to5.0mm/y. Finally, for the large rivers that river capture repeated, we reconstruct the stream nets. It appears an largest displacement of27km in the middle part of the fault zone, and the displacement decreases both to the northwest and southeast along the fault. According to largest river offsets of the different sections, calculated long-term average slip rates of are about4.2mm/a and13.5mm/a since the early Pleistocene and the middle Pleistocene respectively. Data of recovered river offsets showed that the middle and north of southern segment along the fault, since the early Pleistocene, northern and south segment gradually decreases. The fault zone showed active in each section during the Middle Pleistocene. Combing average slip rate, as well as recent activities since the late Pleistocene, find that activities gradually weakened from north to south and inactive in Anpei near, in Vietnam, since the late Pleistocene. Combined with the river ages in these regions, the long term average-slip rates along the fault are assessed. The study helps to understand the Pliocene to present activity along the Red River fault.