new madrid earthquake
In 1812, a magnitude 7.5 earthquake struck near New Madrid, Missouri. The earthquake was strongly felt over approximately 50,000 square miles and altered the course of the Mississippi River. Because very few people lived there at the time, only 20 people died. Many more people live there today (Figure 1.1). A similar earthquake today would undoubtedly kill many people and cause a great deal of property damage. Like the Piedmont Seismic Zone, the New Madrid Seismic Zone is a set of reactivated faults. These faults are left from the rifting apart of the supercontinent Rodinia about 750 million years ago. The plates did not rift apart here but left a weakness in the lithosphere that makes the region vulnerable to earthquakes. Click image to the left or use the URL below. URL:
Intraplate earthquakes are the result of stresses caused by plate motions acting in solid slabs of lithosphere. The earthquakes take place along ancient faults or rift zones that have been weakened by activity that may have taken place hundreds of millions of years ago.
2011 virginia earthquake
In August 2011 the eastern seaboard of the U.S. was rocked by a magnitude 5.8 earthquake. While not huge, most of the residents had never experienced a quake and many didnt know what it was. Some people thought the shaking might have been the result of a terrorist attack. This region is no longer part of an active plate boundary. But if you went back in time to the late Paleozoic, you would find the region being uplifted into the ancestral Appalachian mountains as continent-continent convergence brought Pangaea together. The Piedmont Seismic Zone is an area of several hundred million year-old faults that sometimes reactivate.
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intraplate earthquakes are caused by
--> a) stresses from plate motion acting on the solid lithosphere b) stresses from two plates moving apart c) stresses from two plates sliding past each other d) stresses from subduction
intraplate earthquakes occur due to these types of stresses
a) compressional b) tensional c) shear --> d) any type of stress
intraplate earthquakes may happen at reactivated ancient faults.
--> a) true b) false
the 2011 virginia earthquake
a) was about the same magnitude as the loma prieta quake near santa cruz in 1989. b) did almost no damage. --> c) took place along a fault that was active as pangaea came together. d) all of these
the new madrid seismic zone is in california.
a) true --> b) false
the new madrid earthquake of 1812
a) took place at a lithospheric weakness left over from when rodinia split apart. b) was larger than the loma prieta quake near santa cruz in 1989. c) did very little damage for a large earthquake. --> d) all of these.
--> a) experience earthquakes as they come together. b) do not experience earthquakes as they break apart. c) have few earthquakes. d) all of these.
people who experienced the 2011 virginia earthquake
a) are used to earthquakes. b) knew they were experiencing an earthquake very shortly. --> c) thought the quake might be a terrorist attack. d) all of these
the magnitude of the new madrid earthquake
a) was small compared to modern earthquakes. --> b) altered the course of the mississippi river. c) would now, as then, cause little damage in that region of the u.s. d) all of the above.
only locations that are part of modern plate boundaries can have large earthquakes.
a) true --> b) false
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