Abstract

We use the precise point positioning (PPP) technique to process global navigation satellite system (GNSS) data of 15 continuously operating reference stations (CORS) in Vietnam for the period 2019-2023. After using the sine function to model the series of coordinate components with a fixed period of 351.6 days, the results show that the horizontal component displacement velocities of all CORSs are similar for the entire country. However, in terms of the Up component, stations in the Mekong Delta region have much greater values than the remaining stations. The Up movement velocity of the CORSs in 5 provinces of Tien Giang, Hau Giang, Ca Mau, Bac Lieu, and Can Tho is all downward with a value greater than -12 mm/year. Notably, stations in Can Tho and Bac Lieu provinces have Up displacement velocities of -46.5 and -51.3 mm/year, respectively. We also find that the variation of the PPP Up series at these stations does not entirely comply with the sinusoidal law like normal tectonic plate shifts. This shows that the Up movement of the CORSs in the Mekong Delta region may be affected by subsidence of the construction and subsidence of the local geology