Extensional Seismogenic Stress and Tectonic Movement on the Central Region of the Tibetan Plateau

Abstract

Various earthquake fault types, mechanism solutions and stress fields, as well as GPS and geothermal data are analyzed for the study of the crustal movements on the Tibetan plateau and their tectonic implications. The results show that a lot of the normal faulting type-event concentrated at altitudes greater than 4000 m on the central Tibetan plateau. The altitudes concentrating normal faulting type-events can be zoned two parts: the western part, the Lhasa block, and the eastern part, the QiangtangChangdu region. The azimuths of T-axes are in a general E-W direction in the Lhasa block and NW-SE or NNW-SSE in the Qiangtang-Changdu region at the altitudes of the Tibetan plateau. The tensional stresses in E-W direction and NW-SE direction predominate normal faulting earthquake occurrence in the Lhasa block and the Qiangtang-Changdu region, respectively. The slipping displacements of the normal-faulting-type events have great components in near E-W direction and NW-SE direction in the Lhasa block and the Qiangtang-Changdu region, respectively. The extensions are probably an eastward or southeastward extensional motion, being mainly tectonic activity phenomena in the plateau altitudes. The extensional motions due to normalfault earthquakes are important tectonic activity regimes on the high altitudes of the plateau. The easterly crustal extensions on the plateau are attributable to the gravitational collapse of the high plateau and eastward extrusion of hotter mantle materials beneath the eastern boundary of the plateau. Numbers of thrust-fault and strike-slip-fault earthquakes with strong compressive stress in a general NNE-SSW direction occur on the edges of the plateau.

Numerical simulation of fault deformation and seismic activity in the Southern Qinghai-Tibet Plateau

“…The block and fault physical parameters are listed in Table 1 along with related studies (Zhang et al 1995;Liu et,al. 2003;Xu and Zhao, 2009;Jiang et al 2009;Wang, 2005), in which Young's modulus of the fault is 1/3 of the blocks (Zhu et al, 2015). The triangular surface element PLANE 182 was used to divide the mesh, accurately simulating the irregular model.…”

Numerical simulation of fault deformation and seismic activity in the southern Qinghai–Tibet Plateau

“…These faults were regarded as weak zones, with widths of 6 km. The block and fault physical parameters are listed in Table 1 along with related studies (Zhang et al, 1995;Liu et al, 2003;Wang, 2005;Xu and Zhao, 2009;Jiang et al, 2009), in which Young's modulus of the fault is 1/10 of the blocks (Zhu et al, 2015). The triangular surface element PLANE182 was used to divide the mesh, accurately simulating the irregular model.…”

Moho Interface Changes Beneath the Tibetan Plateau Based on GRACE Data

“…(2004) provided some useful constraints on the surface displacement, and they found that there is a very low tectonic denudation rate (near‐zero levels), and the tectonic activity is weakening in the central plateau (N–N, E–E; N–N, and E). In addition, the thrust faults associated with strong compressive stresses are almost all located on the edges of the plateau (Xu & Zhao, 2009), which are beyond the TP boundary of this study, so the seismic energy accumulation and release processes are considered to have less of an effect on the tectonic displacement of the TP. Therefore, the central plateau is expected to be stable, with little vertical deformation.…”