Preliminary Investigation on Local Solid Earth Tides Variations in Sumatra Island Using Ina-CORS GNSS Network

Abstract Solid earth tides refer to the periodic motion of the Earth’s crust caused by the gravitational forces of the Sun and Moon. In precise geodetic measurements, solid earth tides are a critical source of error that must be mitigated to achieve high accuracy. This study aims to observe variations in local solid earth tides during two significant time periods: when the Earth is at its closest point to the Sun (Perihelion) and at its farthest point (Aphelion). We used multi-day Kinematic Precise Point Positioning (KPPP) to process kinematic data, effectively eliminating discontinuities at day boundaries. Additionally, harmonic analysis with the least squares method was applied to extract tidal generation coefficients in three directions of motion. These coefficients were then compared with theoretical models of solid earth tides, focusing primarily on the largest tidal generation coefficients for amplitude and phase values to identify local variations. Our findings reveal that the lunar semidiurnal coefficient (M2) is the primary tide generator, exhibiting the highest energy percentage. Furthermore, during the Aphelion and Perihelion periods, our results showed no significant differences in tidal ranges at a 95 percent confidence level, indicating that the Sun’s influence on these tidal variations is minimal. Additionally, we compared the differences between observed M2 coefficients, and the theoretical model provided by the International Earth Rotation and Reference Systems Service (IERS) and found discrepancies that led to large tidal residuals, suggesting that local factors, such as geological features, are not fully captured by global models. In conclusion, this study provides valuable insights into understanding local solid earth tides on Sumatra Island.