Differences of geomagnetic anomalous field over Chinese mainland and its adjacent areas during 1960−2000 based on Taylor polynomial model

This study adopts the geomagnetic measurements of the Chinese mainland in 1960.0, 1970.0, 1980.0, 1990.0, 2000.0, and the Taylor polynomial model to build up a medium-scale crustal magnetic anomaly model with low spatial resolution, associated with the fourth-generation geomagnetic comprehensive model （CM4）. The figures of the anomaly field are drawn. The whole trends of the field are studied by putting all measurements into 2000.0. The differences in anomalies among different epochs have also been analyzed by the newest three-dimensional surface spline （3DSS） model derived from all available ground and aeromagnetic data. Results show that the intensity of the northward component X decreases with time, and its distribution shrinks to the southwest; the positive area of eastward component Y gradually moves to the west, and the negative area gradually occupies most of Chinese mainland; the distribution of vertical component Z is stable and is mainly negative in the study area, which implies that other factors do not likely influence the radial component. For the overall distribution of magnetic anomalies, components X, Z, total intensity F and horizontal component H are almost negative, which differs from CM4. Regarding the data consistency, the distribution of F has some similar features to the 3DSS model, which can illustrate more middle and small wavelength structures of the anomaly field. Large differences among the three models mainly come from the different measurement numbers, locations, and modeling theories.