QUANTITATIVE ANALYSIS OF ACTIVITY CHARACTERISTICS OF LONG YAO GROUND FISSURE

Longyao ground fissure is one of the large and hyperactive ground fissures in North China plain. The activity of the fissure has caused damages such as slip dislocation,vertical subsidence and horizontal tension to buildings and highways over the fissure. In order to provide essential data for disaster prevention and mitigation of engineering buildings along the fissure,we carried out field geological survey and OSL dating experiment to ascertain the accurate activity value of Longyao ground fissure. We summarized the horizontal distribution and sectional structure characteristics of Longyao ground fissure at the beginning. Then we determined the strike-slip displacement,vertical dislocation and horizontal tensile width of the ground fissure based on the exploratory trench profile. Finally,we estimated the slip rates of Longyao ground fissure during different periods. Our study results show that the vertical differential settlement rate is the largest on both sides of the fissure,the horizontal strike-slip dislocation rate is the second,and the horizontal tension rate is the smallest. According to the OSL experiment,from 8 ka B.P. to present,the displacement rate of Longyao ground fissure has been increasing. Since the Holocene,the ground fissures have been continuously active and the intensity has been raised constantly. We also found that there were three periods of rapid rise in activity rate.