Comparative analysis the data of two sets VP broadband inclinometers at Jixian seismic station

Jixian seismic station is the only bedrock outcrop in the Tianjin area, with two sets of VP broadband inclinometers installed in Xinshan cave and Xiaoxinzhuang cave respectively. Through comparative analysis of the intrinsic quality, co-seismic response, environmental impact, and instrument maintenance of two sets of VP broadband inclinometers at Jixian station, the following conclusions are drawn. Taking 2023 as an example, the continuity and completeness of the VP broadband inclinometer in Xiaoxinzhuang cave at Jixian station were high, but the completeness of the VP broadband inclinometer in Xinshan cave was relatively low due to human interference and instrument maintenance. The tidal factor stability of both instruments is good, but due to pendulum system failure, the NS accuracy of the Xinshandong cave VP broadband inclinometer is relatively poor. By comparing from 2018 to 2023, the VP broadband inclinometer in Xiaoxinzhuang cave had a clear annual variation pattern, while the VP broadband inclinometer in Xinshan cave had an inconspicuous annual variation pattern, which may be related to the relatively fragmented geological conditions of the regional structure in Xinshan cave. Natural environmental changes such as heavy rainfall and strong winds can have a certain impact on the observation of the two sets of instruments. The Xinshan cave is significantly affected by the pumping around the station. VP broadband inclinometers have a strong ability to record earthquakes, and can clearly record periodic surface waves of several seconds to tens of seconds for far-field earthquakes. For near-field strong earthquakes, they can clearly record the initial arrival of P-waves, but subsequent seismic phase identification is more difficult. A maintenance process was summarized to provide reference for the operation and maintenance of similar instruments, in response to the occasional sudden jumping errors in the EW direction of the Xinshan cave VP broadband inclinometer.