A major earthquake jolted Nepal, India and China on Tuesday, causing widespread panic across the region.The USGS said that the temblor measured 7.4 on the Richter scale and its epicentre was 22 km southeast of Zham city in Tibet region close to the China-Nepal border. Its map showed the epicentre to be within Nepal.Its depth was 18.5 km.An India Meteorological Department official said the epicentre was 60 km southeast of the Lamjung in Nepal where the first major earthquake struck on April 25.China Earthquakes Network Centre said the earthquake measured 7.5 on the Richter scale and it is 10 km deep.