TECTONIC ACTIVITY IN SEMI-ARID AREA OF NORTH CHINA DURING LATE QUATERNARY

The last 0.2 Ma has witnessed very obvious tectonic activity in the semi-arid area of North China.There are many active structures dated as of late Quaternary age in the area,such as normal fault,reverse fault,strike-slip fault,fold,sag,uplift,tectonic landform,tectonic terrace,fossil earthquakes and volcanic structures.The maximum amplitude of the vertical movement is about 88-132m with an average rate of 0.44-0.66 mm/a in the centre of tectonic blocks,and in the active tectonic zone around these blocks the maximum amplitude is about 210-343m with an average rate of 1.05-1.72mm/a,the intensity and rate of the movement contimually increasing.The principal compressive stress trends NE SW and E W.The tectonic activity in the last 0.2 Ma may be divided into 6 stages with ages of about 200,100-70,50-30,10-7,0.7 and 0.3 kaBP,respectively.The most intensive tectonic movement in the late Quaternary fell in the periods of 100-70 and 50-30kaBP.The tectonic reactivation in the semi-arid area of North China is correlative with the uplift of the Tibetan Plateau,serving as one of the controlling factors in the formation and evolution of the arid and semi-arid areas of North China.