Here is an awesome video by a Christchurcher showing how the sediments pouring up through earthquake cracks have the perfect mixture of water and soil to be prone to liquefaction:
I spent a week clearing this crap out of people back yards with the student army of volunteers. They estimate 200000 tonnes of the silt had to be cleared.
For those of us who are not familiar with the term liquefaction. In simple terms, I think it means the soil becomes like quick sand because of the earthquake.
That is really disturbing, and it reminds me of something I just read the other day.
For any Seattle startup folks, just remember that all of Pioneer Square (and then some...) is a liquefaction zone[1]. Also, don't forget that the Viaduct is a death trap, and you really are better off never setting foot (or wheel, I guess) on it.
You mean that bridge that's about a foot above the water level and, when there's a really turbulent storm, can have rough water on one side and calm water on the other, and have waves literally crashing over the cars from the one side of the water?
Nooo, I would have never thought that bridge would be dangerous in an earthquake! </sarcasm>
I'm not intending to mock you, though it's probably coming off that way. Outside of the cool special effects during a storm (seriously, the 'rough water, bridge, calm water' effect is quite eerie), I have no idea why that bridge was built the way it was.
It's about the same with the I-90 bridge too, and you don't even need a storm to see the cool effect of wavy water on the south side and calm on the north side. It always fascinates me when I drive over it. I've only had a spray of water hit my car once so far, I'll make a note to avoid either bridge during an earthquake. ;)
You should also stay in an underground bunker and never go outside, because dude do you have any idea how many asteroids are out there?? The entire surface of the Earth is an Asteroid Impact Zone!
Quite a remarkable video... a little less so when you get to the end and he informs you of the history of Tokyo Central Park (reclaimed land). Still... unbelievable. Much less dramatic that the Google images of entire communities washed from the Earth... devastating.
I've never experienced an earthquake. As such, the cracks and drifting earth make me doubt the reality of such a video. Does this drifting actually occur at the surface like that? Edit: speeling ;-)
I've been in 2 about 20 years ago; both ~5.1. If memory serves there were 2 distict types of shaking. The first was a fairly high frequency vibration that shook the walls and mimic what you see in movies; $#@! flying off shelves, etc.
The second came a few seconds later, and was a slow back and forth horizontal movement of the ground. I remember it being a bit faster frequency than that video shows, maybe about 1Hz, but it seemed like the ground was just moving fairly slowly back and forth a few inches.
I've heard many accounts of these phenomena from others. What I'm having difficulty with is the relative motion of the different pieces of earth. I live on pretty solid ground away from active fault lines. If one of our minor fault lines ever acted up, I could certainly imagine the kind of motion you mention. But if my property "cracked," I'd expect to feel the swaying motion and that each piece of my yard would move in the same direction preventing me seeing the motion. On further consideration that the park in the video is built on a former bay, I supposed the quake could be making the dirt float around on the mushy underside.
The first thing I noticed was an oddness about the crack in the sidewalk. It seems to have cracked perfectly along some crack line that's outside of the sidewalk (not likely - just because dirt cracks underneath doesn't mean the concrete will crack exactly where the dirt does) and there seems to be some rubbery surface where the crack ends in the sidewalk (it stretches as the parts of earth move in different directions.) Not like the pure concrete sidewalks I'm accustomed to, but Tokyo is worlds away and maybe it's not just concrete.
P.S. Why the downvoting on my original post? Is it not a valid question?
That pavement is most likely asphaltic concrete (commonly, though incorrectly, known as "asphalt"), which is a mixture of asphalt and sand/gravel aggregate. It's fairly flexible, at least compared to Portland cement concrete.
I was in the earthquake in Tokyo (a few kilometers from Odaiba where that video was likely taken) and I can say I believe it. Out this far from the epicenter it felt very wobbly. It was like my house was on a block of Jell-o. It felt like a 1-3 htz wave. There was a good three minutes of very strong movement and another severe aftershock a 10-20 minutes afterward.
BTW, The girl having a picnic with her boyfriend when the video starts is shouting こわい (kowai) which means "scary!".
http://www.youtube.com/watch?v=2WoKu5VxKgs
Here is an awesome video by a Christchurcher showing how the sediments pouring up through earthquake cracks have the perfect mixture of water and soil to be prone to liquefaction:
http://www.youtube.com/watch?v=1KqlAMWMjOE