Abstract: To optimize a research method to be used for fault activity intensity in petroleum basins, this study analyzed commonly used parameters to study fault activity intensity, including fault growth index, fault throw, and the rate of fault activity. Then, the new approach was used to calculate the fault throw and the vertical rate of fault activity by the differential tectonic subsidence on both sides of the fault. The characteristics of the Paleogene basement faults’ activity in the Qiongdongnan Basin were studied using the new approach. The results show that the activity of the Paleogene basement faults in the Qiongdongnan Basin can be divided into three phases. In the first phase (from 40 to 36MaBP), the NE tending faults in the eastern Qiongdongnan Basin were strongly active with the fault throw of 800 m and the vertical rate of 200 m · Ma ^{- 1} . In the second phase (from 36 to 30MaBP), the activity of the faults’ trenching in the NE of the eastern Qiongdongnan Basin became weaker, while the faults’ trending in the NW of the western Qiongdongnan Basin became active. The activity intensity of the two different trending faults is similar with the fault throw ranging from 400 - 800m and the vertical rate from 70 to 130 m · Ma ^{- 1} . In the third phase (from 30 to 21MaBP), interior faults of the Qiongdongnan Basin acted more strongly again with the fault throw from 700 - 1800 m and the vertical rate from 80 to 200 m · Ma ^{- 1} , while the boundary faults acted more weakly with the fault throw of 500m and the vertical rate lower than 60 m · Ma ^{- 1} .

Key words: fault activity intensity;tectonic subsidence, vertical rate of fault activity;fault throw, Qiongdongnan Basin