Strange Earthquakes Strike Across the United States
Alabama Earthquakes Stun Residents And Geologists Alike
By Weather.com. Early one morning last November, Jim Sterling was frightened when the ground began shaking outside his 156-year-old antebellum home in Alabama. . .”I heard a boom and felt the shaking,” Sterling said. “It really upset me.”
Since that day, more than a dozen weak earthquakes have shaken western Alabama’s Greene County. Geologists are now working to find out what has caused this swarm over the last seven months, in an area of the South that’s used to large tornadoes but not light tremors.
“It is interesting that recently there has been more activity there than in the last four decades,” said Sandy Ebersole, an earthquake expert with the Geological Survey of Alabama.
Records from the U.S. Geological Survey show the first of 14 earthquakes occurred on Nov. 20, when a magnitude 3.8 earthquake was recorded about 10 miles northwest of the community of Eutaw. The second occurred in mid-December, followed by another in January and three within a few hours of each other on Feb. 19.
The tremors have continued ever since, with the most recent occurring June 6, when a magnitude 3.0 quake rattled the area. All the tremors have been weaker than the initial jolt in November, and Ebersole said some have been too slight for residents to detect. (Read more from “Strange Earthquakes Strike Across the United States” HERE)
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Mysterious Quake Hits Wyoming, One of the Deepest in History
By Matt Walker. A mysterious earthquake that struck the centre of the US was one of the deepest earthquakes of its type ever recorded, say scientists.
The quake, known as the Wind River Earthquake, struck the state of Wyoming in 2013 with a magnitude of 4.7 Mw (Moment magnitude scale). . .
The Wind River area of Wyoming is usually quiet, seismically speaking. In the past 60 years since records have been collected, few earthquakes in the region have been recorded with magnitudes of 4 Mw, while just one surpassed 5 Mw. . .
[T]he region is also tectonically quiet – that is, there is little movement in the Earth’s tectonic plates below the site. The nearest tectonic movement occurs 200 km away to the northwest, at the so-called Yellowstone Hotspot, an area that produces volcanic activity across the states of Oregon, Nevada, Idaho, and Wyoming. . .
Now scientists have evidence that the Wind River earthquake actually occurred deeper within the Earth, in its mantle, rather than within the Earth’s crust.
Their measurements suggest the earthquake occurred at a depth of 75 km.
In the local area, known as the Wyoming Craton, the Earth’s crust is no deeper than 40-50 km, forming part of the cold, stable lithosphere that underlies much of North America. (Read more from this story HERE)
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