天津蓟县地震台两套VP宽频带倾斜仪数据对比分析

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

蓟县地震台是天津地区唯一的基岩出露台,台站两套VP宽频带倾斜仪分别安装在新山洞和小辛庄山洞。通过对蓟县台的两套VP宽频带倾斜仪数据内在质量、同震响应、环境影响、仪器维修等方面的对比分析,得出以下结论:以2023年为例,两套仪器的潮汐因子稳定性均较好,由于摆系故障,新山洞VP宽频带倾斜仪NS向精度比较差。通过2018—2023年对比,小辛庄山洞VP宽频带倾斜仪具有明显的年变形态,新山洞VP宽频带倾斜仪年变形态不明显,这可能与新山洞地质区域性节理发育以及台站周围抽水影响有关。强降雨、气压等自然环境变化会对两套仪器观测造成一定影响。两套VP宽频带倾斜仪均有较强记录地震的能力,能够清晰的记录到远场地震几秒至几十秒周期面波,对于近场中强震可以清晰记录P波初至,但是后续震相识别较为困难。针对新山洞VP宽频带倾斜仪EW向曾经出现的不定时突跳错数的故障,总结归纳了维修过程,为同类仪器运维提供参考。

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.