The epicenter of what’s now believed to be a ‘frost quake’, has been located in northwest Calgary.

A group of researchers was able to pinpoint the location with help from an amateur seismologist who recorded the quake’s seismic signature on his home-built basement machine.

On Saturday, a group led by Dr David Eaton, descended on Captain Nichola Goddard School in Panorama Hills, scouring the frozen ground for signs of prior movement. It didn’t take long before they found a jagged tear in the earth several meters long, at least 50 cm deep and possibly up to a meter deep.

The hunt for physical evidence of the suspected frost quake came after dozens of reports to 9-1-1 and to the CTV Calgary newsroom about a loud “boom” heard and felt across northwest Calgary last Tuesday. Some witnesses said it felt like a small earthquake, others described it as an explosion.

A University of Calgary seismic monitoring station, which could have shed light on the mysterious sound, was offline at the time of the boom. That’s when attention turned to Jeff Zambory, who reached out to CTV to say his basement seismograph captured the data the University’s instruments did not. He was put in touch with Dr Eaton, who used Zambory’s data to zero in on the possible location.

Natural Resources Canada, which had requested Calgarians fill out reports about what they heard March 4th, says it has received more than 280 responses from witnesses. It has produced a map showing the location of all the reports. An official with the organization, Stephen Halchuk, says the “the evidence at the present time indicates that a frost quake is the likely source of the boom.”

The cracks found by the University of Calgary research group are rare physical evidence of a phenomenon that many say they’ve never heard of before. While this is the first recorded frost quake in Calgary, there were several reports of frost quakes in Eastern Canada this winter, where they’ve also been referred to as “ice quakes”.

Frost quakes, also known as cryoseism, occur when prolonged cold temperatures cause water deep in the ground to freeze quickly. That puts pressure on the bedrock, or surrounding frozen soil, causing it to crack. The sudden movement can create loud noise, especially if it takes place close to the surface.