Abstract. The Lo River fault near Tam Dao, North Vietnam, is a young, right-lateral, normal fault which has been active throughout the Quaternary. Rates of dextral slip range between 1 and 2 mm/yr whereas rates of uplift can be estimated roughly at 0.1–1 mm/yr. The drainage deflection and arrangement of shutter ridges suggest 1.5–2.0 km of dextral offset during the past 1–2 millions of years (m. y.), and the height of the youngest faceted spurs averages at 170 m. Analysis of morphometric parametres of the mountain front at Tam Dao indicates that this segment shows properties typical for nearly rectilinear, young normal scarps that belong to class I or II of relative tectonic activity and that are capable of generating strong earthquakes in the future.