Tom Spears
The Ottawa Citizen
October 8, 1997

Three earthquake experts say a newly discovered fault under Lake Ontario adds to the risk that Pickering and Darlington, as well as four U.S. nuclear plants, are on shakier ground than anyone thought.

Seismologists Joe Wallach, Arselan Mohajer and Richard Thomas explored the deepest part of Lake Ontario last May.

They say the bottom of the "Rochester Basin" in eastern Lake Ontario has heaved and cracked during the past 11,000 years — recent time in geological terms.

Mr. Wallach says this shows the same fault that still causes earthquakes along the St. Lawrence River extends well into Lake Ontario, and maybe into Lake Erie as well.

Yesterday, he presented their results publicly for the first time at the annual meeting of the Seismological Society of America’s eastern section in Ottawa.

"That area is not as seismically quiet as people would like to think," he said in an interview.

He estimates an earthquake measuring 7 on the Richter scale could happen somewhere along that fault, and says the greatest danger would be if it damaged a nuclear plant and released radiation.

Big earthquakes don’t happen often. Mr. Mohajer, a professor at the University of Toronto, has estimated a big one might happen once in 10,000 years in western Lake Ontario, near the Pickering and Darlington plants.

But there are plenty of smaller quakes. Ontario Hydro has recorded more than 50 little ones, some too small to feel, in the past six years near the lake’s west end.

There have also been mid-sized quakes in modern history.

Ontario Hydro says it won’t comment until it sees a written version of the Wallach team’s study. Hydro has always insisted it built its nuclear plants strong enough to withstand any earthquake likely to hit southern Ontario.

Mr. Wallach is a consulting seismologist who used to work for the Atomic Energy Control Board. His team descended in a submersible to more than 200 metres beneath Lake Ontario last May, and found sheer drops of 15 metres where the lake bed had shifted.

He says it’s almost proven that this is an extension of the St. Lawrence Valley fault — which was supposed to come no farther west than Cornwall.

And he said the rock that has been sliced and shoved around is brand-new rock, formed since the last Ice Age ended a little more than 10,000 years ago. That shows these aren’t just leftovers from earlier earthquakes.

"There’s a whole series of faults (in eastern Lake Ontario) and they’re geologically young," he said. "If that structure goes through Lake Ontario, and I suspect it does, then it definitely has a bearing on the earthquake risk at the nuclear power plants."

"We’re looking at all these things as contributors to an elevated seismic risk," Mr. Wallach said. "It can’t be ignored."

The new findings are the second evidence of a fault near Pickering and Darlington. Mr. Mohajer and others found a fault running down to Pickering from the north in the early ’90s.

And divers have since found "pop-ups" in the lake near Pickering and Darlington. These are places where the rock on the lake’s bottom has been squeezed sideways and heaved up.

He said plants near the fault zone include four U.S. nuclear stations: the Ginna station near Rochester, the James Fitzpatrick and Nine Mile Point stations near Oswego, N.Y., and the Perry station in Leroy, Ohio.

"The more you learn about the nuclear plants and their circumstances, the more dangerous they seem," said Tom Adams of Energy Probe, a critic of the nuclear industry.