This is a good compendium of the strange sounds that have been heard in many places worldwide in recent weeks. The origin of these sounds is an unknown at this time, but the movement of fault lines have been known to make groaning noises. If this is the origin, then the planet is experiencing deep movement of a type that is not being detected by seismographs, because there is no clear correlation between seismic activity and the sounds. At the same time, the sound is similar to sounds from recent science fiction films such as the roar of the Kraken
from Clash of the Titans and the Tripod sound
from War of the Worlds. Cloverfield2 is in production. So viral marketing is always a possibility. In addition, there are more and more videos appearing on YouTube that are actually dubs of the sound taken from other videos. Nevertheless, the origin of the sounds remains unkown at this time.