A new map shows that reports of a large boom earlier this month – suspected to be a frost quake – came mostly from people living in Calgary’s northwest suburbs.

The map, created by scientists with Natural Resources Canada, was based on 280 surveys filled out by people who heard the boom or felt the ground shake on March 3.

The dots on the map show the reported intensity on a Modified Mercalli Intensity scale, from white as least intense to red as most intense.

Geophysics students from the University of Calgary are also investigating two large cracks in the snow.

Frost Quake Map Canada

(Natural Resources Canada)