High-Precision Vertical Movement of the Tibetan Plateau

Quantitative and high-precision vertical movements are indispensable for resolving the geological diversity of the Tibetan Plateau. In this study, we proposed a joint geodetic adjustment with Helmert iteration algorithm, systematically analyzed its merits with simulated data, and then jointly processed the datasets, including 116,000 km of leveling data, 21 continuous GNSS data sets, and their connecting surveying data, to get a high-precision vertical velocity field for the Tibetan Plateau. The primary results are as follows: (a) Compared with the single leveling data adjustment, the joint Helmert adjustment results of leveling data (i.e., the leveling data and errors are generated by simulation under the first order leveling regulations, which includes 55,708 km, 4605 segments, 4584 points, 22 loops and 40 nodes) and 500 geodetic simulated data (including 2–4 mm/yr errors) demonstrate that the Helmert adjustment can reduce the residual distribution range by roughly 46%; (b) Vertical uplift is dominant on the southern, northeastern, and southeastern margins of the plateau, with uplift rate ranges of 2.0–3.0, 1.0–3.8, and 1.0–2.0 mm/yr, respectively; (c) Conspicuous subsidence is located along the southern portion of the Ganzi fault, with vertical rates ranging from −3.3 to −0.5 mm/yr; (d) Velocity profiles show that vertical deformation varies in different parts of the Tibetan Plateau, which is mostly accommodated by large strike-slip and thrust faults, such as the Kunlun, Ganzi, and Longmenshan faults. Most of the surface uplift is accommodated by crustal shortening in the interior of the Tibetan Plateau; abrupt changes in vertical rates in eastern Tibet and the widely distributed surface subsidence of southeastern Tibet are consequences of crustal flow and gravitational collapse. Overall, the Tibetan Plateau is characterized by continuous deformation, with large spatial variations accommodated by complicated tectonic processes.