Correction method for secular variation in the main geomagnetic field using a field seismogeomagnetic survey

Using the repeated survey data from field stations and the weighted least-squares method, this study obtained the long-term correction results of the measurement data and compared these results with those of current methods. The results were as follows: 1. The new method substantially improved long-term spatial distortion compared to the old method. The secular variation (SV) results of the main geomagnetic field produced by the new method have a higher linear correlation to those of the international geomagnetic reference field (IGRF)_SV model. The mean square error (MSE) of the difference in the three elements F, D, and I between the new method and the IGRF_SV model is 10.7%, 47.0%, and 14.5% of that of the original method, respectively. 2. Applying the new SV correction method obtains more stable and reasonable variations in Earth’s crustal magnetic field. The average amplitude of the Earth’s crustal magnetic field variation in F, D, and I is 28.5%, 55.4%, and 34.4 of the original results, the MSE is 59.1%, 56.5%, and 40.3% of the original results, and the mean gradient is 93.6%, 91.9%, and 97.0%, respectively. 3. In the processed results of the new method, the seismomagnetic information is clearly optimized, and the epicenter location is more consistent with the 0 value line of the Earth’s crustal magnetic field. The processed results of the new method are considerably better than those of the original method and have a higher application value.