黑龙江林口M_B6.4深震前通河地磁谐波振幅比异常特征

Anomalies of the Geomagnetic Harmonic Wave Amplitude Ratio before the M_B6.4 Deep Source Earthquake in Heilongjiang Province

采用黑龙江通河地磁台分钟值数据进行谐波振幅比计算,结果显示:2016-01-02黑龙江林口M_B6.4深源地震前,距离震中150 km的通河地磁台谐波振幅比出现明显异常,异常特征有:1)地磁谐波振幅比Y_(ZHx)和Y_(ZHy)主要表现为"下降-转折-恢复"的形态;2)谐波振幅比异常变化中的转折上升形态具有由深(较长周期)至浅(较短周期)的迁移特征;3)2014-03～2016-01Y_(ZHy)在不同深度出现介质电性不同步异常;4)Y_(ZHy)异常幅度大于Y_(ZHx)异常幅度。异常产生的原因可能是由于西太平洋板块持续以高速度、小倾角向欧亚大陆下方俯冲,林口地震前孕震体应力变化导致地磁台站附近局部介质电性产生变化。

Applying the method of harmonic wave amplitude ratio,we calculate the minute-value data derived from Heilongjiang Tonghe geomagnetic station.The results show that before the January 2,2016 M B6.4 deep source earthquake in Linkou of Mudanjiang city,the harmonic wave amplitude ratio of Tonghe geomagnetic station,about 150km from the epicenter,presents obvious abnormality.There are four anomaly characteristics:(1)the abnormal change of the harmonic wave amplitude ratio Y ZHx in the north-south and Y ZHy in the east-west show the characteristics the form of"down-turning-recovery";(2)The transition features have the characteristics of migration from deep(long period)to shallow(shorter period)in the abnormal change of harmonic wave amplitude ratio;(3)from March 2014 to January 2016,dielectric properties of the harmonic wave amplitude ratio Y ZHy data in Tonghe geomagnetic station have a different abnormality at different depths;(4)abnormal amplitude of the harmonic wave amplitude ratio Y ZHy in Tonghe geomagnetic station is greater than Y ZHx.The reason for abnormal characteristics is that the Western Pacific plate dived under the Eurasian continent at a high speed with a small dip before the M B 6.4 deep source earthquake in Linkou.The stress change of the seismogenic body led to electrical properties of the local medium changing near the Tonghe geomagnetic station.