Swarm of Quakes in Nevada Has Experts Concerned
Swarm of Quakes in Nevada Has Experts Concerned
April 15, 2011MyNews4.com - Nevada Seismologists are keeping a close eye on an area southwest of Hawthorne, Nevada where hundreds of earthquakes have been detected since Sunday.
"It's a little bit concerning in a sense. The largest earthquakes in these sequences are pretty large in size." Graham Kent is Director of Nevada Seismological Laboratory at the University of Nevada Reno.He says there have been hundreds of earthquakes southwest of Hawthorne over the past few days. The largest--recorded at a 4.4 in size.
"These are the biggest in a sequence we've seen at least in the last couple of years."Kent says unlike the 2008 quakes in Somersett that damaged so many homes, these earthquakes are fortunately not underneath a community.
Size is not the only reason Kent says they are watching the swarm of quakes closely. The location of these quakes is on top of a fault that has until now remained unknown or has not been active. Kent then made an eerie comparison,
"Whats really interesting about most of these earthquakes we've experienced... short of the Chilean and Japanese, Haiti, Baha, even Christchurch... were on unknown faults."But Kent says just because those devastating quakes happened on un-named faults does not mean that the series of quakes near Hawthorne will lead to a big quake there. Reno, Carson City and the Las Vegas valley all lie on top of fault lines. And right now, there is no way to predict where the next big quake will occur.
"That's yet another reason why you don't want to look at the map and go phew, I'm safe. We're in earthquake country and so we have to be prepared."
Nevada Continues to Be Shaken by Earthquake Swarm
April 14, 2011Yahoo! - The western U.S. state of Nevada has been rattled in recent days with a number of small earthquakes that are being described as an earthquake swarm. According to the United States Geological Survey, at least 80 small quakes, ranging in size between 1.0 and 4.4 magnitude, have struck the western Nevada area near Hawthorne and Qualey's Camp, near the California border.
The location of this swarm of earthquakes is just west of the Wassuk Range Fault System--about halfway between Bridgeport, Calif., and Hawthorne, Nev.
What exactly is an earthquake swarm? An earthquake swarm is defined as a series of small magnitude earthquakes that occur over a (usually) short period of time in the same or similar location. Swarms can be precursors to larger earthquakes, but that is not always the case. Swarms can also occur in proximity to a volcano and can result from the movement of magma.
Most of these small quakes in Nevada have occurred within a few minutes of each other, with almost daily increases in the number of earthquakes since April 7.
On April 7, one earthquake was registered near Hawthorne at a size of 1.4 magnitude. Three days later, a 1.3 magnitude quake occurred, followed by 3.0 and 3.5 earthquakes within 10 minutes. More than 30 more small quakes that ranged in magnitude from 1.1 to 4.2 struck the same area throughout the day on April 10. A number of small quakes struck in the same time frame a few miles away, much closer to the border between California and Nevada.
About 17 quakes were registered Monday in the same vicinity, but all of the quakes on that date were in the 1.0 to 2.4 magnitude range. Only three earthquakes struck Tuesday, but just after 3 p.m. Wednesday, the largest quake in this swarm struck--a 4.4 magnitude temblor that was followed by three more 3 and 4 magnitude quakes within 10 minutes. A total of 15 quakes struck Wednesday. So far, the activity has continued Thursday with 20 quakes striking so far.
All of the quakes in this swarm have been at depths ranging between 1 and 20 miles.
The USGS characterizes Nevada as a very seismically active state; the state feels small earthquakes on a regular basis. The largest earthquake ever to strike the state was a 7.75 shaker in October 1915. This was the third of three earthquakes that struck northern Nevada within a seven-hour period. It caused damage in Pleasant Valley, Kennedy, Lovelock and Winnemucca. Those earthquakes were felt in locations as far away as Baker, Ore.; San Diego, Calif.; and Salt Lake City, Utah--an area that covered about 800,000 square miles. It was estimated that about 100 aftershocks followed the initial main shock.
Earthquake Swarm in Nevada Continues with Micro-quakes and Salton Buttes Swarms
April 14, 2011geologycrawl.blogspot.com - This is today and yesterday's swarm in Nevada. You see how it is very highly localized, which is very typical of volcanic behavior in spreading zones.
If you look at the low end of the large body of water, you will see some blue squares. That's the Salton Buttes swarm. Also note the cluster of yellow events at the left about two quarters down the map, on the US-Mex border. That swarm is taking place under Signal Hill, and was the site of a good many aftershocks after last years 7.2 mag earthquake to the south of that. It was quiet recently, until this week.The same principal goes for the micro-quakes in Arkansas. A lot of respected people are blaming that quake swam on nearby gas drilling. They fail to realize that this swarm sits in an old area of rifting, and again, swarms are normal in spreading zones. If you Google Earth the Nevada quake swarm, you do not see much human activity other than a small strip mine and some dirt roads. You can't blame the old strip mine. But what you do see is the old lava flow I mentioned before. That flow is an obvious indicator of volcanism. Volcanos cause swarms all the time.
http://earthquake.usgs.gov/earthquakes/recenteqscanv/FaultMaps/116-33.html
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