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M4.7 near Reno, Nevada
Posted on Sunday, April 27, 2008 @ 12:37 pm by Peter Polito
Late Friday night Mogul, NV (just west of Reno) was struck by a M4.7. While a M4.7 earthquake is not terribly large, it was a very shallow quake causing items to fall off grocery shelves, minor rock falls in the surrounding hills, and some of the taller casinos to sway. This quake is the largest thus far in a swarm that began approximately two weeks ago causing seismologists at University of Nevada Reno to issue a statement warning residents of a heightened probability of a larger earthquake.
Source: University of Nevada Reno.
Following an earthquake of this size there is a small increase in the probability of a larger magnitude earthquake in the west Reno area. Citizens should also be aware of the possibility of strong aftershocks from this evenings Magnitude 4.7. Mogul-Somersett residents should expect to feel aftershocks of this earthquake for some time. It cannot be determined if this evenings Magnitude 4.7 earthquake will be the largest earthquake of the 2008 Mogul-Somersett earthquake sequence
The Seismological Laboratory at UNR has posted some terrific products related to this swarm which can be found on their website. The graph below shows clearly how the recent swarm is not just background noise but a true signal:
Source: University of Nevada Reno.
Earthquake Swarm off Oregon Coast
Posted on Monday, April 14, 2008 @ 8:44 am by Dave Schumaker
I may potentially have my computer issues resolved, we shall see. Regardless, I’m back for now! In the past week, there has been a flurry of earthquake activity off the coast of Oregon. While earthquakes in this part of the world are normal, the type and pattern of the earthquakes are puzzling scientists.
The earthquakes are located about 150 nautical miles southwest of Newport, Ore., in a basin between two subsurface “faulted” geologic features rising out of the deep abyssal sediments. The hill closest to the swarm location appears to be on a curved structure edging out in a northwestern direction from the Blanco Transform Fault toward the Juan de Fuca ridge, Dziak said.
Analysis of seismic “decay” rates, which look at the decreasing intensity of the tremors as they radiate outward, suggest that the earthquakes are not the usual sequence of a primary event followed by a series of aftershocks, Dziak said.
“Some process going on down there is sustaining a high stress rate in the crust,” he pointed out.
An article from the Associated Press says that the pattern is similar to those associated with volcanic events. The problem is, there are no known volcanoes in the area.
Scientists don’t know exactly what the earthquakes mean, but they could be the result of molten rock rumbling away from the recognized earthquake faults off Oregon, said Robert Dziak, a geophysicist for the National Oceanic and Atmospheric Administration and Oregon State University.
There have been more than 600 quakes over the past 10 days in a basin 150 miles southwest of Newport. The biggest was magnitude 5.4, and two others were more than magnitude 5.0, OSU reported.
On the hydrophones, the quakes sound like low thunder and are unlike anything scientists have heard in 17 years of listening, Dziak said. Some of the quakes have also been detected by earthquake instruments on land.
[Via ScienceDaily]