Analysis on Deformation Characteristics of Environmental Load at Anqiu Station

Abstract

The Anqiu seismic monitoring station is located on the Tanlu Fault Zone in eastern China, an area where the tectonic activity of the fault has been a central focus of research and monitoring by the China Earthquake Administration. This paper investigates mass loading and tectonic deformation patterns using superconducting gravity data, GNSS data, and water level measurements from the Anqiu station, along with geophysical fluid loading products provided by the IERS Associated Product Centre Deutsches GeoForschungsZentrum GFZ Potsdam. The primary objective is to understand how various loadings—such as surface hydrological, non-tidal atmospheric, non-tidal oceanic, and groundwater loading—affect gravity and deformation at this site. The results show that surface hydrological loading can induce gravity changes up to 2 µGal. A joint analysis of non-tidal atmospheric and non-tidal oceanic loads, using a infinite-layer model of vertical deformation, reveals interannual gravity variations of approximately 3 µGal, strongly correlating with residuals from superconducting gravity data, albeit with a phase shift of about 10 h. The study also finds that vertical deformation caused by non-tidal atmospheric and surface hydrological loads is of similar magnitude, both exceeding that induced by non-tidal oceanic loads, with vertical deformations significantly greater than horizontal ones. Further, GNSS-derived vertical displacement data exhibit a negative correlation with superconducting gravity residuals, although slight discrepancies remain in the detailed variations. After removing non-tidal and hydrological influences, the annual gravity variation is approximately 7 µGal. Subtracting groundwater influences leaves a residual gravity change of about 3 µGal, which may be linked to tectonic activity along the Anqiu-Juxian fault zone. These findings offer valuable insights into the geodynamics of the region and contribute to assessing potential geological hazards.