STUDY OF THE QUATERNARY ACTIVITIES OF THE RED RIVER FAULT (II)-ITS FEATURES OF ACTIVITY, SLIP RATE AND RECURRENCE INTERVALS OF EARTHQUAKES

Since the time when the Red River and its tributaries began their down-culling process up to the present (some 750,000 yrs), the Red River fault seems to have produced 5-6 km right-lateral offset. Using the masimum possible down-culting rate of the river, we. made the estimation that the average slip rate of the fault is 7 mm/yr. Under the offset of such long- term slip, the minimum order of horizontal offset along the fault is 4-9 m. If this offset should be taken as the product of an earthquake, the rccurrc ice interval of seismic events would be 500 to 1,200 yrs. This understanding of ours agrees quite well with the fact that no strong earthquakes along the Red River fault had been documented in the historical record in the past 300 years or so.