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Water, Earth, Sky

Rusty Dennen writes about the environment and the great outdoors.

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Aftershocking

Since Tuesday’s magnitude 5.8 earthquake, there have been five aftershocks of 2.5 magnitude or larger, according to the National Earthquake Information Center in Golden, Colo. The latest were a magnitude 2.5  event at 12:06 a.m today, followed by a magnitude 4.5 jolt at 1:07 a.m..  Yesterday, there was  a 3.4 aftershock at 12:45 a.m., and a 4.2, at 8:04 a.m. Tuesday’s magnitude 5.8 quake at 1:51 p.m. was followed by a 2.8 aftershock at 2:46 p.m. The U.S. Geological Survey says aftershocks could continue for days, or longer, and that there is no way to predict when they will hit, or how strong they will be.  Earthquakes are usually measured on one of two scales, the Modified Mercali Scale, which goes from 1 (detected only by seismographs), to 12 (catastrophic);  and the Richter Scale, measuring magnitude.  According to the Mercali Scale, an earthquake of magnitude 5 to 6  would be felt by people walking, awaken sleepers, sway trees, and  cause  some damage from overturning and  falling objects. But the  scale’s descriptions for a magnitude 6 to 7 quake better describe the damage in Mineral, a few miles from the epicenter, and Culpeper: cracking of walls, downed chimneys  and some damage to buildings.  The Richter Scale, named after Dr. Charles F. Richter of the California Institue of Technology, is logarithmic–an earthquake of magnitude 5.8 is 10 times as strong as a 4.8.  Click here for up-to-date quake information worldwide  from USGS.

Permalink: http://news.fredericksburg.com/waterearthsky/2011/08/25/aftershocking/

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