A seismic expert has refuted an Internet rumor that Sunday's earthquake that killed more than 400 people in Southwest China's Yunnan province was somehow caused by a man-made dam, Beijing News reported.

The 6.5-magnitude quake that struck Longtoushan township, 23 km southwest of the county seat of Ludian in Zhaotong city, sparked interest among Internet users who asked whether large dams built nearby may have been a factor.

"A dam with the capacity of some 20 million cubic meters, such as the Yueliangwan Dam in Ludian county, is not large enough to give rise to the devastating earthquake that struck Yunnan," Chen Huizhong, a researcher with the China Earthquake Administration, told Beijing News.

Chen added that any earthquake caused by a dam usually has a limited scale. The Ludian earthquake would have required a dam more than 100 million cubic meters in capacity and just a few kilometers away.

The dams built in Zhaotong are at least 100 km from the victimized area.

Seismic data also shows that a dam-caused quake often has a hypocenter less than 5 km in depth. The earthquake that hit Yunnan struck 12 km under ground, which also denies the possibility of dam-caused quake.