3D Velocity field of Romania derived from more than 20 years of continuous GPS observations

Abstract The Earth's surface is continuously transformed, with deep and superficial processes contributing to the present-day morphology. Evaluating the contribution of each process and interaction between tectonics, climate, and human activities is difficult, especially in areas with relatively low crustal deformation. With this study, we aim to better understand the tectonic and sub-surface geodynamic processes that result in (small) surface motions in Romania. We are particularly interested in the Eastern Carpathians Bending Zone (Vrancea region), where strong deep earthquakes occur. Furthermore, we are focused on the interaction between the Eurasian, and Aegean tectonic plates. For this purpose, we processed more than 20 years of cGPS data from various networks in Romania (more than 100 stations), using the GipsyX software. To put our results in a broader perspective, we also included similar results published in open-source online literature including countries around Romania. Combining all these solutions we generated a velocitiy horizontal and vertical velocity fields for this extended region. All solutions were converted to the Eurasian tectonic reference plate in the ITRF14 plate rotation model. We find that in general, the horizontal velocity vectors in Romania have small values, ranging from 0.0 mm/yr in the north to 1.5 mm/yr in the south, and notably, the majority of stations indicate a subtle yet significant downward motion of 1.0 -2.0 mm/yr. In contrast, to our expectations, we did not find any significant horizontal and vertical motions in the Vrancea region. The horizontal motions exhibit a strong, generally southward, and gradually increasing trend, starting south of the South Carpathians. The trend is in the direction of the tectonic plates in southeast Europe. It means that the intraplate deformation zone extends to south Romania. The observed patterns contribute to our understanding of intraplate deformation and emphasize the need for continued regional research. Keywords: crustal deformations, GPS, geophysics, tectonics Acknowledgments This paper was carried out within Nucleu Program SOL4RISC, supported by MCI, project no PN23360101, and PNRR- DTEClimate Project nr. 760008/31.12.2023, Component Project Reactive, supported by Romania - National Recovery and Resilience Plan