Ionospheric VTEC anomalies before Ms7.1 Yushu earthquake

:Vertical total electron content is examined to check whether the Ms7.1 Yushu earthquake on April 14, 2010, may have caused any anomalous ionospheric changes. The result shows two TEC increases over the epicenter vicinity on April 1 and 5; these anomalies drifted from east to west, the latter across the whole China. The increase on April 5 was probably related to geomagnetic activity, whereas the one on April 1 may possibly be related to the Yushu earthquake.