Anomalous variations in ionospheric TEC prior to the 2011 Japan Ms9. 0 earthquake

:The ionospheric total-electron-content (TEC) data provided by the International GNSS Service (IGS) network and the VTEC data from the GPS reference stations of Crustal Movement Observational Network of China(CMONC) were processed and statistically analyzed to search for earthquake-related TEC anomalies prior to the 2011 magnitude 9.0 earthquake in Japan. Preliminary results showed that anomalous variations occurred 6 – 11 days and 0 – 4 days prior to the earthquake. After considering solar activity, geomagnetic conditions, and proximity in space and time to the earthquake, we tentatively concluded that the anomalous increase on March 5 may be related to the earthquake.