Current Horizontal Deformation And Motion Mechanism Of Major Tectonic Units And Boundary Zones in North China

Abstract

AbstractBased on the data obtained from the high‐precision GPS measurements carried out in 1992,1995,1996 and 1999 in North China, the relative horizontal motion occurred in two periods (1992–1996 and 1996–1999) botteen the major tectonic units in North China is given in the paper. The results are as follow: (1) Relative to the Ordos unit, the movement of Yinshan unit is of relatively weak left‐lateral strike slip with the amplitude of (0–2.3) ±1.6mm/a and the orientation of about 0°–W13 °N; (2) Relative to Ordos unit, the movement of the Jin–Ji–Lu–Yu unit is right‐lateral extension with the amplitude of (4.4±1.0) –(2.5±1.5)mm/a and the orientation of about S50° −30 °E; while relative to Yanshan unit, it is left‐lateral extensional strike slip with the amplitude (4.7 ± 1.4)–(4.3 ± 1.4)mm/a and the orientation of about E37°–9 °S; (3) Relative to the Jin–Ji–Lu–Yu unit, the Jiao–Liao–Lu–Su unit is characterized by clockwise torsion in the period of 1992–1996. The trend of clockwise torsion is kept with the amplitude of (2.6±1.5)mm/a and the orientation of about W11 °S in the period from 1996 to 1999, showing a right‐lateral strike‐slip movement of extension in the north and compression in the south on the whole. The analysis indicates that current crustal tectonic movement is basically consistent with the current crustal tectonic kinematic property with a little bit difference in magnitudes; Significant fluctuation of the crustal movement with the scale of several years exists, which might be a principal feature for continental crustal movement. The movement in the period of 1996–1999 is different from that of 1992–1996, which is characterized by the strengthening of northward shift of the Ordos unit and the weakening of extensional movement along both sides of the Shanxi graben zone and the Yanshan tectonic zone. It might be resulted from the joint coupling effect of stress accommodatoin after the Zhangbei earthquake and the boundary force of the North China area.