Region may now be seismically hyperactive

The 7.0-magnitude earthquake that hit Sichuan on Saturday occurred on the same Longmenshan fault as the 8.0-magnitude earthquake in 2008.

That has deepened geologists' concerns that seismic activity in the region has entered a hyperactive period, which could endanger the millions of people living along the fault.

Xiong Xiong , a researcher with the Institute of Geodesy and Geophysics at the Chinese Academy of Sciences in Wuhan , Hubei , said the earthquake occurred on the southwestern part of the fault.

The biggest displacement of earth reached 1.5 metres at about 13 kilometres deep on one of the fault's three major subsidiary fault lines, according to the institute's analysis of data from seismic monitoring stations across the world.

The earthquake lasted about 20 seconds, with most of the energy released in the first 10 seconds. It tore apart surface areas within 10 kilometres of the epicentre in Lushan county, Yaan .

In a 2009 paper, Xiong's team warned that the 2008 earthquake, which occurred on the northeastern part of the Longmenshan fault, had significantly increased the geophysical stress on the area that was hit by Saturday's earthquake.