Fracking -- not wastewater disposal -- linked to most induced earthquakes in Western Canada

http://www.eurekalert.org/pub_releases/2016-03/ssoa-fwd032216.php

Public Release: 29-Mar-2016
Fracking -- not wastewater disposal -- linked to most induced earthquakes in Western Canada
Seismological Society of America

A survey of a major oil and natural gas-producing region in Western Canada suggests a link between hydraulic fracturing or "fracking" and induced earthquakes in the region, according to a new report published online in the journal Seismological Research Letters.

The study's findings differ from those reported from oil and gas fields in the central United States, where fracking is not considered to be the main cause of a sharp rise in induced seismicity in the region. Instead, the proliferation of hundreds of small earthquakes in that part of the U.S. is thought to be caused primarily by massive amounts of wastewater injected back into the ground after oil and gas recovery.

The SRL study does not examine why induced seismicity would be linked to different processes in the central U.S. and western Canada. However, some oil and gas fields in the U.S., especially Oklahoma, use "very large amounts of water" in their operations, leading to much more wastewater disposal than in Canadian operations, said Gail M. Atkinson of Western University.

It is possible that massive wastewater disposal in the U.S. is "masking another signal" of induced seismicity caused by fracking, Atkinson said. "So we're not entirely sure that there isn't more seismicity in the central U.S. from hydraulic fracturing than is widely recognized."

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