Solid Earth Tide Analysis of the Trillium Horizon 360 Ultra-Broadband Seismometer at Chongli Seismic Station

Long-period low-frequency waves in seismic records contain crucial information about the adjustment of crustal stress states and the mechanical properties of the medium, and thus hold significant research value. However, their study has long been constrained by the scarcity of systematic observation cases. Solid tides, as a natural and stable long-period signal source in geophysics, serve as a key indicator for evaluating the low-frequency response performance of instruments. This paper, based on the low-noise ultra-wideband reference station built at Chongli Seismic Station under The National Seismic Intensity Rapid Reporting and Early Warning Project, utilized the continuous observation data from the Trillium Horizon 360 ultra-wideband seismometer deployed there in December 2024 to systematically assess the instrument's recording capability of solid tides. The results show that the instrument can clearly record solid tides, with the observed curves having good consistency with theoretical solid tides, and also having a relatively good correspondence with the deformation and tilt observations at the same site. This fully confirms the superior observation environment of Chongli Station and demonstrates that the Trillium Horizon 360 seismometer has excellent capabilities in observing ultra-low-frequency long-period signals. This has significant implications for the recording and study of long-period signals generated by Earth's vibrations.