jgg     2010 30 (5):  24-27    ISSN: 0412-1961  CN: 21-1139/TG IONOSPHERIC VTEC ANOMALY DETECTED BY GROUND-BASED GNSS BEFORE Ms7.1 YUSHU EARTHQUAKE Xiong Jing 1,2) ;Zhou Yiyan 1,2,3) ; and Wu Yun 1,2) 1) Institute of Seismology, CEA, Wuhan 430071 2) Crustal Movement Laboratory, Wuhan 4300713) School of Geodesy and Geomatics,Wuhan University,Wuhan 430079 Received: 1900-01-01  Revised: 1900-01-01  Online: null Supporting info null