Ionospere change before Japan 2011 M9.0 earthquake

Some studies about the ionosphere change before the Japan M9.0 earthquake which occurred on March 11, 2011 have been reported. They found ionosphere anomalies on different days, and the anomalous area is so large that it is nearly impossible to estimate the epicenter location. Here we analyze GIM TEC (total electron content) data from 2011-1-1 to 2011-3-11 with two different methods and found that the TEC anomaly appears on March 8, and the epicenter has the biggest TEC anomaly. This provides a possible method to estimate the epicenter location.