Analysis of Preseismic Anomalies of the Total Electron Content Based on NOAA Data

Based on the data of total electron content( TEC) in the ionosphere released by NOAA,TEC before Mexico's two earthquakes,respectively on March 20th and April 12th,2012,was analyzed by using the point to surface method. The findings confirmed that preseismic anomalies of TEC existed and were manifested as: point-calculated epicenter TEC oscillogram showed TEC on March 7th,15th and 18th,before the March 20th earthquake were abnormal,and TEC on April 4th and 11th,before the April12th earthquake were abnormal. Area-calculated TEC distribution indicated TEC of epicenter's neighboring areas increased or decreased conspicuously comparing with other areas before the earthquake.