基于S变换的唐山四分量钻孔应力时频特征分析

以2016-02～11期间唐山四分量深孔地应力连续观测数据为基础，使用S变换技术获得区域构造信息的时频特征，讨论其与近场小震及远场大震事件的关联性。研究发现，唐山台近场25 km范围内5次小震事件发生前的数日内，其地应力连续观测数据的S变换结果在720～1 440 min周期范围内均表现为高能量簇异常，且与潮汐因子的日常形态存在显著差异；2016-04-15日本九州M7.0级地震的同震效应主要对地应力S变换结果中周期小于240 min的频段具有较大影响，因此，唐山地应力高能量簇特征可能来自于区域构造应力场动态调整，而非远场大震的同震效应，说明地震事件前后的构造应力时频演化特征与近场地震活动可能存在较高的前兆关联性。

Analysis of Time-Frequency Characteristics of Four-Components Borehole Stress at Tangshan Station Based on S-Transform

Based on the continuous stress observation data of four component deep borehole in Tangshan from 2016 February to November, we calculate the time-frequency characteristics of tectonic information in the Tangshan area using the S-transform technique. We analyze the consistency between the earthquakes with magnitude larger than 3.5 and the continuous observation data of crustal stress. The results show that there is a high frequency energy cluster existing from the 1 440 min to 720 min cycle range before the earthquake, showing great diversity with the tide factor. We used observations before and after the April 15, 2016 M7.0, Kyushu, Japan, earthquake to study the coseismic effects of large earthquakes in the far field. The results show that the far-field seismic events mainly affect the frequency bands less than 240 min, which means the high frequency energy cluster may come from the dynamic adjustment of regional tectonic stress field. In our opinion, there is a high precursory correlation between the time frequency evolution characteristics of tectonic stress and the earthquake events.