Characteristics of geomagnetic Parkinson vector in Chinese mainland and their tectonic implication

In this paper， the geomagnetic preferred planes， Parkinson vectors and their errors at 36 geomagnetic stations of the Chinese mainland are calcu-lated with the methods of geomagnetic difference-vector and complex transfer function. The results show that for these observatories in the southern portion of North China， Central China and South China (containing Guiyang and Shao-yang) and the coastal observatories， the lengths of Parkinson vectors increase as the period decreases， which indicates the conductivity structure in shallow is more horizontally inhomogeneous. However， for the observatories of western China， such as Lhasa， Tonghai， Xichang， Chengdu， the lengths of Parkinson vectors increase as the period increases， which indicates in the deeper there are more clearly horizontal differences in conductivity. On the Chinese mainland， there are obviously some convergence and radiation regions of Parkinson vectors， among Parkinson vectors of the stations in Qinghai-Tibetan Plateau and around the Bohai Sea cohesive; however those in the Ordos block diffuse. For the coastal observatories exists a more clearly seacoast-effect. For the stable blocks， such as North China plain， the lengths of Parkinson vectors are shorter， suggesting that the conductivity structure of these blocks are close to layered levelly. In addition， the inclination and dip angle of the preferred plane inferred from difference-vector algorithm are almost consistent with those calculated from Parkinson vector formula， and agree well with those obtained from transfer function.