Analysis of water tube tiltmeter observation affected by reservoir load

The NE component curve of DSQ water tube tiltmeter at Yixian seismic station in Hebei Province had a downward trend since February 14, 2022. The annual change curve was different from that of previous years. Combined with the simulation results of three-dimensional concentrated load model, it is shown that the total reservoir capacity of Wanglong reservoir reached 279.50×10⁴ m³ from February 14 to April 6, 2022. The theoretical value of tilt change was 1.27×10⁻⁷, which is higher than the limit index of tilt interference of 1.455×10⁻⁸. It was inferred as the main factor causing the abnormal change of NE component acceleration of water tube instrument at Yixian station.