Computer Analysis of Total Electron Content in the Earth's Ionosphere in Problems of Searching for and Detection of Earthquake Precursors: Current Problems and Challenges

The article reviews methods for the computer analysis and detection of so-called ionospheric earthquake precursors. It is shown that the applied techniques lead to quantitatively incomparable results due to the differences in determination of a reference undisturbed variation and in quantitative criteria of considering disturbances anomalous. As the existing techniques do not take into account the known sample standard deviation (provided by NASA along with the global ionospheric maps of total electron content for the Earth's ionosphere), the amplitude of revealed anomalies cannot be compared to the level of natural variability of the ionosphere. To eliminate this shortcoming, we propose a few metrics to determine numerical criteria that enable to classify as anomalous the total electron content disturbances observed before strong earthquakes.