This quantitative exploratory study analyzes the variation of the total amount of vertical electrons (vTEC) in the ionosphere, in 25% or more of the circular area of 1000 km of concentric radius to the epicenter of each earthquake major than M7.0 degrees during 2015. 13 telluric events have been analyzed. The vTEC data used for the analysis are the variations of ranges calculated with statistical data analysis, using software developed in INTI-Lab. These data are mapped in each region for each hour, they have been considered 18 days before the event. The minimum unit of temporal analysis is 1 hour. The minimum unit of surface analysis are rectangular areas of latitude 2.5 ° x longitude 5 °. It found that the area of 25% was covered with a vTEC in 100% of the events during 2015. This manifested in 8.77 days approx. The variation was maintained during 34 hours of the 432 hours analyzed, in a 7.87% of the time. It should be mentioned that the vTEC values have been analyzed and it was found that during 2015 the maximum variation of vTEC before an earthquake was 15.98, and the minimum -0.989. This study is a quantitative analysis that shows evidence of the significant presence of the vTEC before an earthquake, the final objective is to analyze the viability of an earthquake risk from vTEC variations in the ionosphere and this analysis is an advance significant in our overall objective.