Dragonsbain
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Registration Date: 18-04-2011
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Thank you Becky. Each region has it's local everday disasters. I work with three guys that all moved from California. They were being gentle yesterday.
They all knew that this quake was minor for them but HUGE for us. It was agreed that it is dangerous to be in an earthquake on the East Coast. We don't build for it. Thus all the damage that is being recorded.
Just for note, I didn't feel the earthquake. Also the difference in the geology. The following is from the GEEKTECH.
Due to the positioning of the North American Plate boundary and nearby fault lines, the West Coast sees a lot of activity. Because of all this activity, the crust along the West Coast is generally a lot hotter and also a lot weaker in comparison to the East Coast, where the plate boundary is further out to sea. Seismic waves find it much easier to travel through colder, stronger, less abused areas of the Crust than more offset surfaces such as in California. As Holly explains:
“The West Coast is worse due to the collision of the Pacific and North American plate, creating the San Andreas fault line. The East Coast's closest plate boundary is Mid-Atlantic ridge, and that's pretty far away from it! [The East Coast's crust is] cooler and stronger, but [it] does not necessarily have a thicker crust though. But the colder surface definitely makes waves travel faster!â€
The actual bedrock can have an impact on how earthquakes travel. In Virginia, the Piedmont contributes to the Appalachian Range, created millions of years ago, out of very old rock. The mountain ranges were created out of faulted marine sedimentary rocks, volcanic rocks and were part of the original Pangaea supercontinent. The old and faulting rock of the Appalachian range, combined with the coolness of the east coast, and potential activity in the Seismic Zone encourages further-moving waves due to reverberation. The breaks in the bedrock of California usually stop this kind of reflex.
“Virginia is part of the Appalachian Range, so a similar formation to Scotland and Norway [once all of these countries were attached and the range ran throughout]--very old rock squashed in Pangaea supercontinent collision 440 Ma [million years ago]," Holy tells us. "This created loads of faulting, hence the wide spread of seismic propagation.â€
When you bring all these factors together, it makes a clearer picture as to why the Virginia quake carried so magnificently: cool, barely-ruptured ancient ground combined with an activity zone will let a sudden powerful surge energy equivalent to 7000 tons of TNT less than 4 miles from the surface travel at a fair pace across lots of connected faults and fault lines to reach other parts of the continent.
Of course, why such a sudden moderate-heavy quake happened at such a shallow depth is yet to be really uncovered--perhaps it's a mystery fault that went previously undetected--but if there's one thing that geologists, seismologists, and scientists can agree on, it's that the Earth will always continue to surprise.
I hope all of this explains a little. I'm offering a bit of comfort to those same three guys that have never been a hurricane before. I was in Hurricane Andrew.
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25-08-2011 01:26
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amethyst
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I am a Condor.
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Registration Date: 15-07-2009
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Yeah, lived through Loma Prieta. Fortunately I was north of San Francisco at the time in Napa. However, I have very close ties to the other two cities that took major damage. I was born in Santa Cruz and my mother's family is from Hollister. Many of the buildings that I remember from my childhood in both towns are gone. Not damaged, but gone. I remember watching the fire that swept through the Marina District in the city.
Radio, phones, tv all were disrupted. I think radio and TV came back within 20 minutes to a half hour for those areas that had power. Being where we were, we were lucky. I had an uncle in Hollister and one in San Jose that we couldn't contact because of damage.
That one was felt throughout the San Andreas fault which means, it was pretty much felt from just north of Los Angeles to north of Santa Rosa.
But I suppose it's like the few times we get a twister stronger than a dust devil out here. I don't get wound up, but some do. Now we ever have a hurricane out on this end of the Pacific, then maybe I'll get uptight. Heck, we don't even get the monsoons that Asia and Hawaii get. Although, we might have had a few El Nino storms that make us wonder, I doubt they are on the same level.
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25-08-2011 04:54
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