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Geoff Blewitt, a University of Nevada physicist who focuses on measuring minute earth movements with GPS, believes that since the swarm began, a 20-square-mile area has shifted eastward one centimeter – just under a half-inch.
The shift is too great to be caused by the swarm itself and hints that a deeper, underground creep is straining the region above it, Blewitt said. The swarm could be partially releasing that strain.
The Component box gives a selection between "Short period", "Long period" and "Very long period". Data shown on this page are all recorded on the vertical component of a broadband seismometer, which records in the frequency range 0.0083-50Hz. However, to look at the data it is useful to apply a filter. The "Short period" data are bandpass filtered in the frequency band 3-8Hz and typically show local earthquakes. The "Long period" and "Very long period" data are lowpass filtered and only contain frequencies up to 1Hz and 0.1Hz respectively. Both can show earthquakes at a large distance from the station. Large local earthquakes can show up on all the plots.
Nevada has a complex plate-tectonic environment, dominated by a combination of extensional and transform motions. The Great Basin shares some features with the great Tibetan and Anatolian plateaus. All three have large areas of high elevation, and show varying amounts of rifting and extension distributed across the regions. This is unlike oceanic spreading centers, where rifting is concentrated narrowly along the plate boundary. The numerous north-south mountain ranges that dominate the landscape from Reno to Salt Lake City are the consequence of substantial east-west extension, in which the total extension may be as much as a factor of two over the past 20 million years.
The extension seems to be most active at the eastern and western margins of the region, i.e. the mountain fronts running near Salt Lake City and Reno. The western Great Basin also has a significant component of shearing motion superimposed on this rifting. This is part of the Pacific - North America plate motion. The total motion is about 5 cm/year. Of this, about 4 cm/yr takes place on the San Andreas fault system near the California coast, and the remainder, about 1 cm/year, occurs east of the Sierra Nevada mountains, in a zone geologists know as the Walker Lane.
As a result, Nevada hosts hundreds of active extensional faults, and several significant transform fault zones as well. While not as actively or rapidly deforming as the plate boundary in California, Nevada has earthquakes over much larger areas. While some regions in California, such as the western Sierra Nevada, appear to be isolated from earthquake activity, earthquakes have occurred everywhere in Nevada.
In Nevada, gold mines drink a desert dry
Quest for riches puts future at risk
By Kirk Johnson
Published: FRIDAY, DECEMBER 30, 2005
ELKO, Nevada: Just outside the chasm of the biggest open-pit gold mine in North America, there is an immense, ever-flowing oasis in the middle of the Nevada desert. It is an idyllic and isolated spot where migratory birds often alight for a stopover. But hardly anything about it is natural.
This is water pumped from the ground by Barrick Gold of Toronto to keep its vast Goldstrike mine from flooding, as the third-largest gold company in the world carves a canyon 1,600 feet, or 485 meters, below the northern Nevada aquifer.
Gold mines drain nearly 10 million gallons, or 38 million liters, a day in the driest state in America and the fastest growing one, propelled by the demographic rocket of Las Vegas. It is just one of the many strange byproducts of the tangled Nevada love affair with gold.