An earthquake expert says a northeast Ohio well used to dispose of wastewater from oil and gas drilling almost certainly caused a series of 11 minor quakes in the Youngstown area since last spring.

John Armbruster of Columbia University said Monday that it might take a year for the wastewater-related rumblings in the earth to dissipate even though the Youngstown well was closed last week to allow for research on the seismic activity.

Brine wastewater from oil and gas drilling operations is often disposed of in wells called injection wells.

Armbruster said injection wells, like the one in Youngstown, have also been suspected in quakes in Arkansas, Colorado and Oklahoma.