亚失稳态野外观测证据

2010年1月24日,山西省河津市发生了MS4.8级地震,在此之前,山西临汾地震台VP型宽频带倾斜仪2009年的观测数据清晰地记录到与实验室岩石破裂失稳过程类似的图像:4—7月观测数据以准线性变化为主;8月出现偏离线性的非线性变化;10月达到峰值点之后开始缓慢下降,此阶段即亚失稳阶段;12月出现加速下降;12月21日转平。转平之后35d距离观测台站89km处的河津市即发生了MS4.8级地震。在准线性阶段(岩石破裂实验的应力积累阶段),发震断层及附近的Benioff应变曲线也出现同步加速现象。这表明临汾地震台VP型宽频带倾斜仪所记录的亚失稳态现象是来自震源的信息。实验室观测到的亚失稳现象可在野外观测数据中得以验证。

Outdoor Observation Evidence of the Meta-Instability State

The similar image of rock rupture process was recorded clearly in laboratory by the broadband tiltmeter of Linfen station before the 2010 Hejin MS 4 .8 earthquake .In 2009 ,the observation data from April to July ,were based on almost all linear variation ;Nonlinear variation deviating linear appeared in August ;Data began to drop slowly after the peak reaches in October ,and that is a stage of sub‐instability ;Data appeared quick drop in December and turned flat on Dec .21 .35 days later , the earthquake of MS4 .8 occured 89 km away from the observation station .In the stage of quasi‐linear (stress accumulation stage of rock rupture test ) ,seismogenic fault and Benioff strain curve accelerated at the same time ,indicating that the sub‐instability phenomena recorded by VP‐type broadband tiltmeter of Linfen station was from the hypocenter . The sub‐instability can be proved through outdoor observation data .