On the streets of Mexico City, a rather odd occurrence has been spotted. Videos (above) shared by residents on social media show patches of roads rising and buckling as if the road was “breathing.” It almost seemed as if a large animal beneath the city were emitting giant sighs.

Once the videos were shared on social media, scientists began pitching in with theories of what could be causing this, and turns out the reason was simple – the deadly earthquake that hit Mexico City in September this year.

Geophysicist Mika McKinnon has argued that liquefaction due to the earthquake is causing the undulation. She explained that since Mexico City is built on a base of sediments, seismic activity can can cause this phenomenon when the waves pass through the area. The sediment particles begin to flow like a liquid. The waves then turn into breath-like pulses when they reach the surface of the asphalt.

Seismologist Susan Hough added that the cause can be confirmed with certainty once Mexican authorities have the chance to examine the ground beneath the road.