Lore:Pocket Guide to the Empire, 1st Edition/Cyrodiil - The Unofficial Elder Scrolls Pages (UESP) Pocket Guide to the Empire said:
From the Odes:
"He was born in Atmora as Talos, 'Stormcrown' in the language of the ancient Ehlnofey, and it was from that shore he sailed. He spent his youth in Skyrim among the Nords. There he learned much from the Tongues and their chieftains and their ways of war. At twenty he led the invasion of Old Hrol'dan, taking it back from the Witchmen of High Rock and their kinsmen.
"Soon the Greybeards made known that they were restless. Already the storms had begun from their murmurs. The Greybeards were going to Speak. The surrounding villages were abandoned as the people fled the coming blast.
"The villagers warned Talos to turn back, for he was marching to the mountain where the Greybeards dwelt.
"Inside he went, and on seeing him they removed their gags. When they spoke his name the World shook.
"The Tongues of Skyrim told the son of Atmora that he had come to rule Tamriel and that he must travel south to do so.
"And it is true that Talos did come to Cyrodiil shortly after the Battle of Old Hrol'dan.
"And it is true that a great storm preceded his arrival."
The Greybeards speaking causes the world to shake. Todd Howard himself confirms this is literal.
http://www.gameinformer.com/themes/...im-s-dragon-shouts&GroupKeys=&PostPageIndex=1 Skyrims Dragon Shouts (Game Informer) said:
In the lore, Tiber Septim was the first main emperor. He could shout. His way of the Voice was unmatched,” Howard explains. “He is the original guy who walks the seven thousand steps and talks to the Greybeards. And the idea is, at that time, that they were so powerful they had to have all the villages flee for miles. This little kid is walking up this snowy mountain, and all these people are packed up and they’re walking down and away. Because they know the kid is going up to talk to these guys, and when they talk there’s going to be avalanches.”
The Greybeards of the 4th Era do this too, once again shaking the world.
And yes, this is literal, once again confirmed by Todd Howard.
nerdtrek.com/skyrim-details/
Interview with Todd Howard said:
Todd Howard: The greybeards, the guys who live up on the throat of the world, who are the masters of the voice, they find out about this fairly quickly, and they shout your name. They shout Dovahkiin to the wind, and it kind of rumbles through the world. The mountains shake when they call you. And you think ‘what was that,’ and someone says ‘that was the greybeards calling you. To walk the 7,000 steps up the throat of the world to meet them.'”
What's more, it was felt in Winterhold by.
http://en.uesp.net/wiki/Skyrim:Urag_gro-Shub Skyrim said:
Dovahkiin: What about the Dragonborn?
Urag_gro-Shub: What about... wait. Are you? Were you the one the Greybeards were calling?
So yeah, it's literal. Not shaking the perspective; it rumbles through the world and shakes the mountains, and indeed the entire world. Looking at the mercalli chart, it would rank at a IV or V.
That would be about a 5 on the richter scale.
There's two ways this can be done; non-seizemic and seizemic. For now we'll go non-seizemic. Circumference of the Earth is 40,075km, half of which is 20037.5km (though it takes 20011km at best, so we'll go with that). Using
this impact calculator and fiddling with the numbers until we get the
right numbers, which is 1.55 x 10^16 Joules, or 3.69 megatons of TNT equivilent. That's it? I expected more. Still impressive though. And if it's seizemic, it'd be far higher.
Dovahkiin tanks the full strength of the Greybeards shouts at point blank and is completely unscathed. Speaking of, incase it wasn't clear from the game itself, the strength of the shout depends on the power of the shouter. The Greybeards sans Argneir are too powerful to even speak.
Arngeir Skyrim said:
Dragonborn: Why don't the others talk?
Arngeir: Their Voices are too powerful for anyone not trained in the Way to withstand. Even a whisper could kill you.
Final Results
The Greybeards shout = 3.69 megatons 
That would be about a 5 on the richter scale.
There's two ways this can be done; non-seizemic and seizemic. For now we'll go non-seizemic. Circumference of the Earth is 40,075km, half of which is 20037.5km (though it takes 20011km at best, so we'll go with that). Using this impact calculator and fiddling with the numbers until we get the right numbers, which is 1.55 x 10^16 Joules, or 3.69 megatons of TNT equivilent. That's it? I expected more. Still impressive though. And if it's seizemic, it'd be far higher. Dovahkiin tanks the full strength of the Greybeards shouts at point blank and is completely unscathed. Speaking of, incase it wasn't clear from the game itself, the strength of the shout depends on the power of the shouter. The Greybeards sans Argneir are too powerful to even speak.
Arngeir
