高台YRY钻孔应变仪与BBVS-120地震仪青海玛多M S7.4地震同震对比分析

Coseismic Comparative Analysis of Gaotai YRY Borehole Strain Gaugeand BBVS-120 Seismometer of Maduo M S7.4 Earthquake in Qinghai

以高台台秒采样YRY-4钻孔应变仪记录的2021-05-22青海玛多M S7.4地震观测数据及同址观测的BBVS-120地震仪重采样秒数据为研究对象,进行观测曲线变化特征、地震学震相及频谱特征对比分析。结果发现,钻孔应变仪秒采样数据同震记录清晰,满足四分量钻孔应变观测的自检特性。两套仪器均能记录到玛多地震的震相数据,且震相形态相似,到时基本一致。两套仪器的频率谱及时频分布形态相似,频谱成分接近,但频率分布和幅值变化存在差异,这与仪器的观测原理、分量(测向)方位、频带宽度及观测灵敏度等有关。为进一步分析钻孔应变仪的动力学意义,对仪器进行不同时间节点的空间投影,结合震中与台站的相对方位进行分析,发现接近震中指向台站SW-NE向分布的2323、2324分量和垂直于震中指向台站分布的2321、2322分量受力状态相反,可能与P、S波传播规律有关。

We study the data of Maduo M S7.4 earthquake in Qinghai province on May 22,2021 recorded by second sampling YRY-4 borehole strain gauge and the resampling seconds of BBVS-120 seismometer observed at Gaotai station.We carry out comparative analysis of data variation characteristics,seismological phase morphology and spectral characteristics.We find that the coseismic record of borehole strain second sampling data is clear,and the coseismic record satisfies the self-check characteristics of the four-component borehole strain observation.Both sets of instruments can record the seismic phase of the earthquake,the seismic phase morphology is similar,and the seismic phase arrival time is basically the same.The frequency spectrum and time-frequency diagram of the two sets of instruments are similar,the spectrum components are close,but the frequency distribution and amplitude change are different.This is related to the observation principle,component(direction finding)orientation,frequency bandwidth and observation sensitivity of the instrument.To further analyze the dynamic significance of borehole strain,we conduct space projection of borehole strain at different time nodes,and combined with the relative orientation of the earthquake epicenter and the station,we find that the southwest northeast 2323 and 2324 components,which are approximately close to the epicenter pointing station,and the 2321 and 2322 components distributed perpendicular to the epicenter pointing station,are in opposite tension and compression states.This may be related to the propagation laws of P and S waves.