The calculation method of the location of the singular generalized current source according to synchronous measurements of the magnetic field in the remote points is proposed. It is designed for the continuous monitoring of changes of the degree of electromagnetic heterogeneity of the geophysical environment. Regular fluctuations of the apparent distance to the effective single source were recorded according to the magnetic data of the observatories in Japan 2009-2011. They are connected with the rhythm of the geodynamic processes in the vicinity of the station Kakioka. The most significant decrease in the apparent distance was registered in connection with the seismic activation of the region, including the catastrophic earthquake of March 11, 2011 with a magnitude of M = 9.1. The anomalous behavior of the apparent parameters of the generalized source was displayed not less than two weeks before the earthquake. Characteristic changes of the curves were registered in the period of three months.