ON TEC ANOMALIES BEFORE THE WENCHUAN EARTHQUAKE

The case study of the strong TEC disturbances observed before the Wenchuan earthquake of May 12, 2008, M 7.9, D 19 km, (31.0N; 103.4E) as possible seismo-ionospheric precursors is presented. Strong local long-living TEC deviations from the quiet non-disturbed conditions that (i. e. anomalies) linked to the near-epicenter region followed by the similar effects at the magnetically conjugated area are discriminated using differential TEC maps derived from the Global Ionospheric TEC Maps provided by the NASA. TEC anomalies were observed 2 days before the Wenchuan earthquake and looked like local TEC increase for more than 60% in magnitude. They occupied similar to 10 deg. in latitude and similar to 40 deg. in longitude at the near-epicenter region and existed from 06 UT till 12 UT May 9, 2008. The geomagnetic situation for the considered time period was quiet, therefore, the investigated TEC anomalies were rather unlikely to be triggered by the geomagnetic or solar activity.