The number of noticeable aftershocks related to the Great East Japan Earthquake that rocked northeast Japan in March 2011 had reached 9,577 as of Monday, the Meteorological Agency said.

The tremors are continuing to rattle the country two years on, though with lessening frequency, the agency said.

Yoshimori Honkura, chairman of the government's Earthquake Research Committee, said it will take several more years before the rate returns to the predisaster levels.