Syzdekistan

This morning at 6:16:05 A.M. a magnitude 6.0 earthquake struck near Wells Nevada. Not only was it a fairly powerful earthquake, it was shallow (9 km deep) and close to Wells (12 miles east). It did a lot of damage to the historic storefronts in Wells including knocking down facades and brick walls and littering the streets with debris. Luckily only one person was injured. It also broke a water main, started several fires, and was felt from California to Wyoming. The largest city that felt significant shaking was Salt Lake City whose newsaper has a good article on the quake in Wells.

The Flying J Truckstop in Wells shared several security camera angles of the earthquake:

Location map from the USGS.

The USGS has all kinds of interesting data on the quake including a variety of maps, estimates of the number of people affected by differing amounts of shaking, and scientific data. Here is the current tectonic summary of the quake:

The seismological data from this earthquake show that it occurred on a normal fault that trends roughly north-south and has a dip of 30-60 degrees. Based on the location, depth, trend of fault, and proximity to mapped active faults, the earthquake likely occurred on the west-dipping Independence Valley fault system. The fault zone bounds the western margin of the Pequop Mountains, which are located about 30 km east of Wells, Nevada. The entire fault system is approximately 64 km long and consists of a zone of subparallel range-front normal faults.

The most recent surface rupture on the Independence Valley fault zone likely occurred several tens of thousands of years ago. Independence Valley, which lies to the west of the fault, was filled by Lake Clover during the time of the last major glacial advance about 15-20,000 years ago. The fault does not cut the highest shorelines of this lake, which indicates that the most recent movement on the fault predates the lake. In addition, a recent geological study to investigate the history of fault movements estimated that the most recent large earthquake that caused surface rupture occurred at least 42,000 years ago (Wesnousky and others, 2005). Smaller earthquakes that didn’t rupture the ground surface likely have occurred more frequently on the Independence Valley fault zone.

Earthquakes in Nevada are not uncommon. One of the most significant sequences of earthquakes in the western U.S. occurred in Nevada during the first half of the 20th century. The sequence started in 1915, when a magnitude 7.3 earthquake occurred in Pleasant Valley south of Winnemucca. The sequence culminated with a series of four major earthquakes that ranged in magnitude between 6.6 to 7.1 in 1954 the vicinity of the Carson Sink and Dixie Valley. This sequence of earthquakes defines the Central Nevada Seismic Belt.

The geologic expression and studies of the Independence Valley fault zone indicate a relatively low long-term rate of activity, but this event demonstrates that the fault remains active and has the potential to generate larger earthquakes. It is noteworthy that the geologic expression of this range-front fault is similar to hundreds of other faults throughout the Basin and Range Province of the western United States.

Wesnousky, S. G., Barron, A. D., Briggs, R. W., Caskey, S. J., Kumar, S., and Owen, L., 2005, Paleoseismic transect across the northern Great Basin, USA: Journal of Geophysical Research, v. 110, B05408, doi:10.1029/2004JB003283.

This quake was the largest in Nevada since 1954. Nevada is the third most seismically active state (after California and Alaska) but its extremely low population density make damaging quakes rare. Most earthquakes in Nevada occur in western Nevada and there have been a number of large ones. For more information on large Nevada quakes, check out this link to the USGS.
Finally, I must stress that the Richter Scale is a measure of the amount of energy released in the earthquake. More important to the people affected by the earthquake, is the intensity of the earthquake. This is measured by the Mercalli index. The Mercalli scale ranges from:

1-Felt by people in favorable conditions
12-Total Damage: Almost everything is destroyed.

The people of Wells experienced a 6: Felt by all; many frightened and run outdoors, walk unsteadily. Windows, dishes, glassware broken; books off shelves; some heavy furniture moved or overturned; a few instances of fallen plaster. Damage slight.

Looking at the damage in Wells, I wonder if this might be upgraded a bit once seismologist takes a look at the damage.

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