Magnitude of Chatham-Kent, Ont., earthquake downgraded slightly
What's the science behind what makes the earth shake?
Earthquakes Canada has downgraded Friday afternoon's minor earthquake in east Chatham-Kent Ont., from a 2.7 magnitude to a 2.5.
There were no reports of any damage, the agency said on its website.
Allison Bent, a seismologist with Natural Resources Canada, says they made the call to downgrade its severity after studying more data.
"These are kind of on the threshold that people would feel if it's near a populated area, which this one was," Bent told CBC Radio's Afternoon Drive guest host Josiah Sinanan.
"If it was in a more remote area, it would only have gone noticed by our instruments."
Matthew Myers, a volunteer firefighter who lives in Ridgetown near the epicentre, was home at the time when it happened.
"I just walked in the front and all of a sudden I just heard like this big bang and the house shook," he said. "I honestly thought someone hit the house with the car. It was confusing and concerning — just like really quick."
Bent says for the Lake Erie area, while still fairly uncommon, larger earthquakes normally originate from places such as Ohio, and not from the north side of the watershed.
"With large earthquakes, the shaking is sustained. So you feel a lot of that back and forth vibrations. With the smaller earthquakes, it's so short that sometimes when you feel it, it's hard to tell whether it was an earthquake, whether it was explosion, whether something hit the building. That is fairly typical."
Earthquakes Canada says earthquakes with a magnitude of under 3.5 are generally not felt, but they can be recorded on local seismographs.
Chatham-Kent police said they received several calls that afternoon from people who believed there was an explosion near Ridgetown, with numerous structures "experiencing tremors."
Emergency services responded to attend the areas in question, but no explosions were located. It was later determined to be the result of a minor earthquake.
A larger earthquake was experienced the same afternoon on the country's west coast in B.C.
The 4.7-magnitude earthquake hit near the seaside community of Sechelt just before 1:30 p.m. PT, according to Earthquakes Canada.
The agency said earthquakes are caused by the slow deformation of the outer, brittle portions of the earth's outermost layer of crust and upper mantle.
"Due to the heating and cooling of the rock below these plates, the resulting convection causes the adjacently overlying plates to move, and, under great stress, deform," Earthquakes Canada says on its website.
"Sometimes, tremendous energy can build up within a single, or between neighbouring plates. If the accumulated stress exceeds the strength of the rocks making up these brittle zones, the rocks can break suddenly, releasing the stored energy as an earthquake."