Thread: All Shook Up

I was about 25 miles from the epicenter and it really shook the building. At first we thought it was a train and then realized there are no train tracks close enough to our studio to cause that kind of rumble. It started as a low rumble and then turned into a mild roar as it peaked. We left the building ASAP since there was nothing to get underneath of and I noticed the large panes of glass on the front of our building were waving around like water even though they are about 6.5 mm thick. No damage or casualites except some computer equipment that shook and fell to the ground. I'm quite concerned about possible hidden structural damage to various buildings and infrastructure. One of the bridges had a big chunk of concrete come off of it and several others are being checked for less obvious damage. Quite strange to go through that and it felt like the entire building I was in was about to come tumbiling down but thankfully it did not. It was a long quake with about 25 to 30 seconds at its peak magnitiude of 5.8 and 6.0 closer to the epicenter.

That sounds very similar.

It's strange that the noise is what really got my attention before the ground moving. It was only after,
that I thought of how much the ground was actually moving. Maybe it was because I was too busy
moving myself.

It was felt in Ontario Canada too... probably at greatly reduced intensity but my house shook for about 40 seconds and things were waving around and moving on the tables... no damage though. The apartment building next door emptied out in a hurry and pretty soon the whole neighborhood was having this mass discussion about "What just happened?" .... Evreyone was ok, no surprises, we were almost 800km from the epicenter.

A couple of local news stories were explaining that East Coast temblers tend to be felt over very large areas... but wow.

5.8 I believe. I have been hearing that 5.8 on the east coast can be stronger than 5.8 on the west.
Something to do with the difference in the plates. I guess the seismographs measure the magnitude
the earthquake one way and people and buildings see it a little different. Anyway, it definitely got
your attention.

The east coast has a pretty big fault line. I experienced one in New York long time ago.

AFAIK, a 5.8 is a 5.8 no matter where you are. It's not a weak quake, but we're used to them out here in California, so it doesn't seem like a big deal. Plus, all our buildings are well designed for earthquakes, so we don't have all the brick structures falling down like you had out there. The main difference between the two coasts has to do with the plates. California is "younger" geologically speaking (this is why the Sierras are higher and sharper, and the Appalachians are lower and more rounded), and has many, many more faultlines and small pieces of plate. Those faultlines act as a damper, as the seismic waves have a harder time crossing them. The eastern part of the US and Canada is more like one giant piece of rock, with relatively few faultlines and separate pieces of plate, so the wave travels much longer distances. There's also several types of seismic waves that affect how an earthquake feels (sharp and jolting, or rolling). They have different wavelengths, speeds and energies, so the depth of the epicenter and your distance from it affect what type of waves you feel. In my very non-scientific experience, the shallower a quake, or the closer I am to it, the more of the sharp, jolting waves I feel, and the deeper or farther away I am, the more "rolling" I feel.

@VirtualAce: Being mounted to a concrete pad on the ground is more likely to collapse your building, since the energy travels straight up into the walls. Many of the big buildings here are built on what amount to giant springs and rollers. That actually improves the building's ability to withstand an earthquake since the ground can move under the building with some of the energy being absorbed by the springs, and the rollers allowing the building to "stay in place" while the ground moves under it. In actuality, the building still moves a great deal. The top floors of a high rise can move dozens of feet side-to-side, while the bottom floor stays relatively stable. A bit scary the first time, looking out your office window feeling like you're sailing the high seas, but better than the top snapping off and falling to the ground.