BIG QUAKE IN WASHINGTON D.C. REPORTED BY KOKESH!!

[Rydher Profile]

how in the F is this possible...

I have some family in South Jersey and Philly, can't get through no surprise there. But talking to my mom on the phone we both thought the same thing. 5.9 is a good size quake but to be felt that far seems odd. Then again, I'm not an expert on plate tectonics.

[Annieem Profile]

Felt it in the mountains of Pennsylvania....at 1:55 pm....my whole building shook! Scary stuff!

[Annieem Profile]

It was the noise that first got my attention. Sounded like a muffled jack hammer at first, then the noise became louder. Windows started to vibrate, Items in my shop began swinging....

[Rydher Profile]

My dog just now came out of the corner and is acting completely normal now. It's an odd coincidence for sure. Do you think a dog can really sense an earthquake that far?

[Slamgunshark Profile]

My dog just now came out of the corner and is acting completely normal now. It's an odd coincidence for sure. Do you think a dog can really sense an earthquake that far?

Most definitely, animals are special.... very special.

[domdabears Profile Website]

It went as far west as Illinois it said.
I didn't feel anything up here in the Chicago area though.

[Rydher Profile]

Makes you wonder what else your missing out on being 'civilized'.

[Rydher Profile]

Why Was Virginia’s Earthquake Felt All The Way in Canada?

Today’s 5.8 magnitude earthquake centered in Virginia. So why are there reports of tremors being felt as far away as Canada, North Carolina, Georgia and Michigan? According to the U.S. Geological Survey (via Live Science), it’s because the East Coast experiences quakes differently than the West Coast, where they are more common:

“The crust is different in the east than in the west,” USGS earthquake geologist David Schwartz told LiveScience. “It’s older and colder and denser, and as a result, seismic waves travel much farther in the east than in the west.” Additionally, said Andy Frassetto of the Incorporated Research Institutions for Seismology, the sediments along the east coast can make quakes feel stronger. “The sediments of the coastal plain along the eastern seaboard can trap waves as they propagate and produce a minor amplification of the shaking,” Frassetto told LiveScience.

NPR has more specifics on the east-west comparison:

California is a tectonically active area. The state is situated along the San Andreas Fault, where the North American and Pacific tectonic plates meet.

Virginia sits about smack in the middle of the North American plate, where “intra-plate seismicity” — that is, seismic activity within a plate itself, rather than at a plate boundary — causes the occasional earthquake.

According to USGS, earthquakes that take place to the east of the Rocky Mountains are felt over 10 times a longer distance than those to the west. Virginia is classified at “moderate” risk for earthquakes.

USA Today reported seismologist Karen Fischer of Brown University as saying that earthquakes of this magnitude are unusual but not unheard of:

Virginia is not on an active earthquake fault and is roughly in the middle of the North American continental crustal plate, she says. But it has residual fault scars left over from 200 million to 300 million years ago, when it was an earthquake zone, at the time when the Atlantic Ocean rifted apart from Europe.

“We are just seeing pressure build up and release on those scars,” Fischer says. “There is a lot of debate on exactly what is going on down there and exactly how quakes this big happen in this kind of crustal zone.”



This graphic created by USA Today shows the range an epicenter of Tuesday's earthquake. (USA Today Research)

According to USGS, there have been about 200 earthquakes in Virginia since 1977. Tuesday afternoon’s earthquake ties for the largest with the largest quake ever experienced on 1897 at 5.8 magnitude

[Mediasorcerer Profile]

Wow, I got the chills. I'm in Sarasota, Florida and while no earthquake. My dog is acting fucking weird, just sitting in the corner of the house and won't move. Not like him at all.

As a side note, take a look at Alaska HAARP. There have been little blips for that 2.5 frequency areound the time of the Colorado quake. I'm not convinced of HAARP, just something to take note of.


Edited to say: The reason I got the chills is because not even 20 minutes ago I was talking to my coworker on the phone and noticed the dog being like that. Cable is out, so no TV, only internet news.

dogs are very clever ,hope u are ok ryder,shit!

[Shaggietrip Profile]

Yup its cut and paste but good info.



This graphic shows the thickness (in kilometers) of the North American lithosphere. The blue area is about 250 km thick and composed of a 3-billion-year old craton underlain by younger lithosphere deposited as ocean floor subducted under the continent within the past billion years. The green, yellow and red areas are younger and thinner continental lithosphere added around the margins of the original craton, also by subducting sea floor. The thick broken line indicates the borders of the stable part of the continent. Credit: Barbara Romanowicz and Huaiyu Yuan, UC Berkeley

The continent of North America is not a single, thick, rigid slab, but is instead more similar to a layer cake, with a section of 3-billion-year-old rock sitting atop much newer material, a new study that probes the depth of the continent finds.

The finding helps explain how the Earth's continents formed, researchers said.

"This is exciting because it is still a mystery how continents grow," said study researcher Barbara Romanowicz, director of the UC Berkeley Seismological Laboratory.

"We think that most of the North American continent was constructed in the Archean (eon) in several episodes, perhaps as long ago as 3 billion years, though now, with the present regime of plate tectonics, not much new continent is being formed," Romanowicz said.

How cratons form

The Earth's original continents started forming some 3 billion years ago when the planet was much hotter and convection in the mantle more vigorous, Romanowicz said. The continental rocks rose to the surface and eventually formed the lithosphere, Earth's hard outer layer that includes the planet's crust and a portion of the upper mantle.

These old floating pieces of the lithosphere, called cratons, apparently stopped growing about 2 billion years ago as the Earth cooled, though within the last 500 million years, and perhaps for as long as 1 billion years, the modern era of plate tectonics has added new margins to the original cratons, slowly expanding the continents.

One of those original continents is the North American craton, located mostly in the Canadian part of North America.

The history of the Earth's oldest continental plates is vague, because details of their interiors are hidden from geologists. The deep interior of the North American craton is known only from so-called xenoliths — rock inclusions in igneous rock (formed from molten magma) — or xenocrysts such as diamonds that have been delivered to the surface from deep below by volcanoes.

Seismologists, however, have the ability to probe the Earth's interior thanks to seismic waves from earthquakes around the globe, which can be used much like sound waves are used to probe the interior of the human body.

Such seismic tomography has established that the bottom of the North American craton is about 155 miles (250 kilometers) deep at its thickest, thinning out toward the margins where new chunks have been added to the continental lithosphere.

The new study suggests that any continental lithosphere that has been added since the original North American craton formed came from material scraped off of the ocean floor as the craton plunged beneath the continent – and not deposited from below by plumes of hot material welling up through the mantle, as happens at volcanoes and mid-ocean ridges on the seafloor.

Layered continental cake

Romanowicz and UC Berkeley postdoctoral fellow Huaiyu Yuan found the boundary between the old craton and the younger material while using a new seismic technique to locate the boundary between the lithosphere and asthenosphere, the softer material below the lithosphere on which the continental and oceanic plates ride.

Instead, they found a sharp boundary 93 miles (150 km) below the surface, far too shallow to be the lithosphere-asthenosphere boundary. The scientists think the sharp boundary is between two types of lithosphere: the old craton and the younger material that should match the chemical composition of the sea floor. Their interpretation fits with studies of xenoliths and xenocrysts, which indicate that there are two chemically distinct layers within the Archean crust.

Another study conducted three years ago that also used seismic waves to probe the Earth's deep layers found a sharp boundary at a depth of about 75 miles (120 km).

"We think they are seeing the same layering we are seeing, a sharp boundary within the lithosphere," Romanowicz said.

Romanowicz thinks their study will help scientists further tease apart the formation of the continents.

"I think our paper will stimulate people to look more carefully at distinguishing the ages of the lithosphere as a function of depth," she said. "Any information we can provide that constrains models of continental formation is really useful to the geodynamicists."

The study is detailed in the Aug. 26 issue of the journal Nature.

Source: http://www.ouramazingplanet.com/north-america-lithosphere-cratons-studied-0489/