广东惠东M_(L)4.6地震前地磁逐日比内源电流解释

Source current mechanism of the daily ratio of geomagnetism before the M_(L)4.6 earthquake in Huidong,Guangdong province

距离大亚湾核电站约50 km的汕尾—潮州断裂上在2022年3月14日发生了惠东M_(L)4.6地震,1911年在相同位置发生了一次6级地震.本文根据惠东M_(L)4.6震前提出的地磁逐日比短临异常意见的预测范围,以华南沿海地区10个地磁台站的地磁观测数据为例,使用日变化畸变时段的积分效果来量化异常的分布,探讨此次地磁逐日比计算中干扰对结果的影响程度,并利用内源环电流作为源,开展与地磁逐日比异常相关的源电流机理解释.结果显示,对噪声干扰大的地磁台站数据做滤波处理,能够有效去除其影响,提升逐日比计算可信度;提出面积补偿法对异常日的弱日变化幅度作补偿,得到接近正常的日变化幅度,面积差在平面上的分布也较好地反映异常中心与震中位置的密切关系;根据三层导电体中电流变化的趋肤深度估算方法,模拟了环电流感应磁场的叠加,它可能弱化了Sq电流引起的地磁垂直分量日变幅度并导致地磁逐日比出现异常.

About 50 km away from Dayawan Nuclear Power Station,a M_(L)4.6 earthquake occurred at the Shanwei-Chaozhou fault on 11 March 2022.There was an earthquake as large as M6.0 occurred in same site.In this paper,based on the geomagnetic observation data of 10 geomagnetic stations in coastal areas of South China,the integration effect of the diurnal variation distortion period was used to quantify the distribution of anomalies.we discussed the degree of interference and the decisive factors in the calculation according to the prediction range of the day-to-day ratio threshold,and the internal source ring current is used as the source to explain the source current mechanism related to the geomagnetic day-to-day ratio anomaly.The results show that filtering the geomagnetic station data with large noise interference can effectively remove its noise,improving the credibility of the day-to-day ratio calculation.It is proposed that the diurnal variation amplitude of the geomagnetic vertical component is mainly controlled by the Sq current system,which may be related to the space weather activity of the ionosphere and is obviously dependent on local time.Estimating the skin depth of the current change in the three-layer conductor and combining with the results of other geophysical explorations,we believe that the position where the ring current is generated may be located at the most intense exchange between the asthenosphere hot material upwelling to the lithosphere material,about 100 km underground.Therefore,we calculate the induced magnetic field distribution caused by the ring current superimposed on the surface at a depth of 100 km.The magnetic field generated by this internal source current weakens the vertical geomagnetic field caused by the Sq current.Themagnitudeofthe Z-component changes day by day,which eventually leads to an anomaly in the day-to-day ratio of the geomagnetic field.