Five new mobile earthquake monitoring stations have been set up in quake-hit Yushu county of Qinghai Province to improve ability for monitoring aftershocks, the China Earthquake Administration said Thursday.

There were just a few earthquake monitoring stations in Yushu, according to the administration.

The new stations, run by migrant quake monitoring workers with Qinghai and Sichuan provincial seismological bureaux, would help authorities to gain more knowledge about the quake zone and have better judgement on future trend of the disaster, the administration said.

Altogether nine aftershocks above magnitude 3 had been monitored in Yushu by Thursday noon since Wednesday's 7.1-magnitude quake, according to the China Earthquake Networks Center.

On average, the Chinese mainland suffered from two earthquakes at or above 7 magnitude every three years, four quakes at or above 6 magnitude and 20 at or above 5 magnitude every year, the center's vice director Zhang Xiaodong said at Thursday's press conference.

The world has been struck by 10 earthquakes at or above 7 magnitude since the start of the year, he said.