华北地磁感应矢量时空特征分析  

The spatio-temporal characteristics of geomagnetic induction vectors in North China

作　　者：王桥[1] 黄清华[1] 

机构地区：[1]北京大学地球与空间科学学院地球物理学系,北京100871

出　　处：《地球物理学报》2016年第1期215-228,共14页Chinese Journal of Geophysics

基　　金：973计划(2014CB845903);国家杰出青年基金项目(41025014)资助

摘　　要：在验证了Robust方法求取地磁转换函数的可靠性之后,将之应用于华北13个台站超过5年的地磁数据中,得到了地磁感应矢量的时间变化序列.结果发现,在各个台站及其不同周期的地磁感应矢量时间变化序列中,都不同程度地存在明显的年变背景特征;使用谐波拟合法提取了其中的长期背景(大于6个月)成分.重点分析了640s周期的地磁感应矢量时间变化序列,结果发现大多数台站的长期背景变化相位一致,显示出较明显的季节性变化特征;根据对其统计分析得到的特征量在空间上的分布特征推断,华北盆地在壳内可能存在一相对高导层;去掉其长期背景成分后的频谱分析显示,地磁感应矢量存在大约一个月的周期特征,这可能与地磁活动的太阳自转周期(27天)变化有关.More than five years′variations of geomagnetic induction vectors for 13 geomagnetic stations in North China were obtained by using the robust estimation method,which has been verified and compared with the ordinary least square and the weighted least square methods.We proposed the following three principles of selecting a specified period of the results from the robust estimation method：（a）the relatively higher coherency between horizontal and vertical component at this period,（b）the much more stable results of the robust estimation at this period,and（c）the skin depth within the crust for the period.After investigating the stability of coherency resulting from different time window（one day and ten days）,we chose the results with640 second period for all stations finally,to be analyzed forward.Significance annual background variations were revealed from the time series results of the geomagnetic induction vectors with640 second period,and were extracted the long-term background（more than six months）from them using the Fourier harmonic analysis.A similar phase variation was obtained for most station excepting DAL,BJI and JIH stations,possibly related to different underground conductive structures.The further statistical analyses of the geomagnetic vectors of BJI,JIH,LYH,WHN,HUH and TAY stations indicated that a relatively higher conductivity layer might existaround these stations,while the results of QIX,TSY,LZH,TAA and MAL stations showed some complexity of the electrical conductivity structures in the crust.After removing the longterm background from the time series,we found that there exists a rough monthly variation of the geomagnetic induction vectors.Such period variation is consistent with the geomagnetic activity index,and may relate to the period of the solar rotation.

关 键 词：华北地区 地磁感应矢量 时空变化特征 电导率异常 

分 类 号：P318[天文地球—固体地球物理学]