Nanaimo, B.C. — Was it a sonic boom, a dynamite blast, or an asteroid hitting the earth?

Government and local emergency services were stumped Wednesday afternoon, unable to explain a powerful blast that shook Nanaimo from stem to stern.

The blast, which occurred around 1 p.m., was heard and felt as far south as Chemainus, and as far north as Nanoose.

Nanaimo RCMP say no damage or injuries had been reported.

One thing is fairly certain: it was not an earthquake, although it did register on a seismograph in Nanaimo.

"From the signature of the wavelength, it does not look like an earthquake, it looks like an explosion," said Alison Bird, an earthquake seismologist with the Geological Survey of Canada.

When talking about atmospheric sound "focusing", what the're really referring to is a phenomenon similar to a rogue wave. Just like waves in the water, sound waves in the air can travel at different speeds depending on their power and amplitude. When waves overtake each other, they can cancel each other out, or they can briefly combine and create a "rogue sound wave"...a noise that can be just as loud as the original blast (imagine standing two miles from a dynamite explosion, and hearing it as if you were two feet away). The waves will loose synchronization and break up quickly, but they can create a tremendous blast for the brief period of time they exist.

These waves REQUIRE an inversion layer to reflect the sound waves along the ground and keep the sound focused enough to get a decent wave overlap. It's uncommon to have an inversion layer low enough to do that, a sound big enough to be noticeable, and people standing in the area the amplified waves are focused in, but it does happen.