Mesozoic structural deformation and tectonic stress field characteristics in the north of Qinshui basin

The article analyzes and summarizes the structural deformation and tectonic stress field characteristics of the north Qinshui basin based on studying the folds,faults,and joints.The results indicate that the trends of the structure line in different area ares diverse,in the west the structure lines are mainly NE-SW trending;in the east the structure lines are mainly almost SN or NW-SE trending;in the center the structures lines are mainly almost E-W trending.The characters of the folds,fractures,joints and the drainage all manifest that there was almost SN compression in the study area which happened during the Late Paleozoic and the Mesozoic.The azimuth angle of the maximum principal stress is from 161° to 174°,the dip angle is less than 10°,which may be the response of Indosinian tectonic activities.In addition,there may be NW-SE trending compression in the study area which happened during the period from 165±5 Ma to 136 Ma,and the azimuth angle of the maximum principal stress is 152°,the dip angle is 1°.