洞体形变短临异常HHT时频分析

Application of HHT method in the short-term and impending anomaly analysis of cavity deformation

利用HHT方法,对河津M_L 5.2地震前30天临汾盆地数字化洞体形变观测资料进行分析,计算不同观测手段、不同测向的瞬时振幅、时频谱及边际谱参数。结果表明,震前约14天,在水平摆和垂直摆边际谱上同步出现低频扰动波,且水平摆NS向时频谱伴随频带较宽的高频成分;震前2天侯马水管倾斜仪EW向瞬时振幅出现连续高值异常,时频谱表现为高频成分增多。分析认为,洞体形变观测数据的时频谱变化,可能显示了各阶段震源体激发的不同频段信息。

The short-term and impending anomaly, recorded by the digital observation instruments of cavity deformation at Linfen Seismic Station before Hejin M_L 5.2 earthquake, was analyzed by HHT method. We calculated the instantaneous amplitude, time-frequency spectrum and marginal spectrum parameters of different observation instrument and components from one month cavity deformation observation data before the M_L 5.2 earthquake. The preliminary results show that： The low frequency disturbance wave occurred in the marginal spectrum from the horizontal pendulum and vertical pendulum about 14 days before the M_L 5.2 earthquake, and the timefrequency spectrum of NS horizontal pendulum accompanied with high frequency composition of the wide band; The instantaneous amplitude of EW water tube tiltmeter at Houma station appeared continuous high value anomaly about 2 days before the M_L 5.2 earthquake, and the time-frequency spectrum displayed increasing high frequency composition; The whole evolution process probably indicated that different precursor wave information motivated by seismic source at every stage had short-term and impending prediction significance.