Abstract Based on mathematical or MATLAB language, this paper improves the geomagnetic low-point displacement method and software. This paper replaces the manual drawing with the automatic drawing technology of geomagnetic abrupt boundary to eliminate the random error. The idea is to realize automatic mapping by establishing the geometric analytical relationship between the abrupt boundary and the geomagnetic low-point time of the station network. Voronoi subdivision is done for the geomagnetic network, and the trend of the abrupt boundary is limited to the Dirichlet tessellation line of the geomagnetic network. Then the low-point time isoline is calculated by nearest neighbor interpolation. Finally, the low-point time contour map is transformed into the second order contour map, so as to extract the abrupt boundary. We replace the original GMT with the local time of geomagnetic station to eliminate the low point time deviation caused by longitude effect. The idea is to establish the functional relationship between station GMT, station longitude and local time, then input station GMT and station longitude to output the station local time. This paper takes a geomagnetic low-point displacement phenomenon on July 20, 2017 related to the Jiuzhaigou MS7.0 earthquake as an example to evaluate the improved method.
