西安地震台新、旧山洞VP型垂直摆观测资料对比分析

COMPARATIVE ANALYSIS OF VP VERTICAL PENDULUM OBSERVATION DATA OF NEW AND OLD CAVES AT XI’AN SEISMIC STATION

西安地震台新、旧山洞相距约200 m,在引洞进深、覆盖层厚度、观测环境等方面存在差异。现基于2020年新、旧山洞两套VP型垂直摆倾斜仪观测资料,从数据完整率和连续率、观测波形记录固体潮情况、强远震同震响应、内在质量等指标方面进行对比分析。结果表明,新山洞垂直摆数据完整率和连续率均大于旧山洞垂直摆,而且新山洞垂直摆记录潮汐波形清晰、稳定性较好,旧山洞垂直摆波形较易出现趋势转变、潮汐波形畸变等,稳定性较差;在记录同震响应方面,新山洞垂直摆同震响应持续时间更长、突跳幅度更大;在内在质量方面,新山洞垂直摆潮汐因子稳定性明显高于旧山洞的,其潮汐因子中误差也优于旧山洞的,利用均方连差法计算的新山洞垂直摆非潮汐部分噪声水平稳定性能也更好。

The new and old caves of Xi’an seismic station are about 200 m apart.There are differences in depth of the approach tunnel, the thickness of the overburden, the observation environment and so on.Based on the observation data onto two sets of VP vertical pendulum tiltmeters in new and old caves in 2020,a comparative analysis is made from the aspects of data integrity and continuity, solid tide recorded by observation waveform, co-seismic response of strong and distant earthquakes, internal quality and other indicators.The results show that the data integrity and continuity rates of the new cave vertical pendulum is greater than that of the old cave vertical pendulum, and the tide waveform recorded by the new cave vertical pendulum is clear and stable.The tide waveform of the old cave vertical pendulum is prone to trend change and tidal waveform distortion, and the stability is poor.In terms of recording co-seismic response, the duration of co-seismic response of vertical pendulums in Xinshan cave is longer and the sudden jump amplitude is larger.In terms of internal quality, the stability of the tidal factor of the vertical pendulum of the new cave is significantly higher than that of the old cave, and its mean square error of the tidal factor is also better than that of the old cave.The noise level stability of the non tidal part of the vertical pendulum of the new cave calculated by the mean square continuous difference method is better.