Present‐day crustal thinning in the southern and northern Tibetan Plateau revealed by GPS measurements

Abstract

GPS measurements from sites within the Tibetan Plateau show not only east‐southeast‐west‐northwest extension but also, more importantly, horizontal dilation throughout the interior of the plateau. Assuming conservation of volume, vertical (thinning) strain rates equal horizontal dilation rates, and they, 8.9 ± 0.8 nanostrain a−1 and 7.4 ± 1.2 nanostrain a−1 in northern and southern Tibet, and 12.0 ± 3.2 nanostrain a−1 in its southwestern part, suggest no measureable difference. Principal extensional strain rates also are similar in magnitude and orientation. If crustal thinning began at 10–15 Ma and the current rates of horizontal dilation applied both to the entire crust and to that period, the crust should have thinned by 5.5–8.5 km. If isostatic equilibrium applied, the mean elevation of the plateau would have dropped ~1 km. The similar rates for northern, southern, and southwestern Tibet suggest that the processes dictating crustal extension, normal faulting, and crustal thinning in the three regions differ little from one another.

Interseismic Deformation of the Altyn Tagh Fault Determined by Interferometric Synthetic Aperture Radar (InSAR) Measurements

“…Consequently, we assumed a strike-slip fault with 90˝dip angle. We assumed that LOS deformation is a combination of fault parallel deformation and vertical deformation, ignoring normal fault deformation, which is justified by GPS measurements [11]. We modeled the fault as a buried infinite screw dislocation in a homogeneous, isotropic elastic half-space, where aseismic slip occurs at a rate (s) below a locking depth (d) during the interseismic period.…”

“…This method can localize a given deformation field in space and scale as well as detect outliers in the observation set. Based on the relative less normal deformation from a GPS study [11], we resolved the along-fault velocity using ascending and descending track LOS velocities and used it as the total horizontal velocity. Then we extrapolated the velocity field of this area using the Kriging interpolation method (Figure 7a).…”

“…GPS study [11], we resolved the along-fault velocity using ascending and descending track LOS velocities and used it as the total horizontal velocity. Then we extrapolated the velocity field of this area using the Kriging interpolation method (Figure 7a).…”

“…The red arrows with ellipses show the GPS velocity projected to the rough fault line. The GPS velocity is from Ge et al [11].…”

Contemporary crustal movement of southeastern Tibet: Constraints from dense GPS measurements

“…Global Position System (GPS) measurements have been widely used to constrain the horizontal crustal deformation of Tibet16171819, indicating that Tibet is currently undergoing eastward block motion and clockwise rotation due to the ongoing collision between the Indian and Eurasian plate. Meanwhile, the vertical crustal deformation throughout Tibet at different spatial and temporal scales (e.g.…”