Determining tectonic plate movement velocity and local subsidy of some continuously operating reference stations (CORS) in the Mekong delta in the period 2019 – 2024

Abstract

The Mekong Delta (MD) is gradually sinking, becoming a major concern of scientists and the State in recent years, due to the worrying impacts of global climate change and humans. This study analyzes the displacement of the MD tectonic plate from 2019–2024 based on CORS data and the precise point positioning (PPP) method. The PPP coordinates are standardized according to the ITRF2020 coordinate system to ensure consistency. The results show that the average velocity of the MD in the three components North – East – Up is (-8.6, +27.8, -25.9) mm/year, respectively. The displacement in the ground component of these stations is similar to that of other CORS stations nationwide. However, the displacement velocity according to Elevation is more than 8 times higher, confirming the influence of local subsidence. The largest is in Bac Lieu with -51.4mm/year. After eliminating the influence of tectonic plate movement (using Rach Gia station as a reference), we determined the local subsidence rate of the station in Can Tho to be -41.3 mm/year and Bac Lieu to be -46.4 mm/year. This shows that the overall subsidence in the Mekong Delta is mainly due to local subsidence rather than tectonic movement. At this subsidence rate, after just over 40 years, these stations will be below sea level.