April 30, 2008

Scientists Trying to Make Sense of Recent Earthquakes

A recent surge of seemingly endless earthquakes in Nevada over the past two months have seismologists puzzled as they try to determine whether the quakes indicate more activity to come.

"You're not going to get an earthquake prediction today," John Anderson, director of Seismology Laboratory at the University of Nevada, Reno, said Tuesday during a briefing with Gov. Jim Gibbons and emergency managers on the seismic activity.

Hundreds of quakes began hitting the Reno, Nevada area on Feb. 28. The largest came Friday night reaching a magnitude of 4.7, registered at 11:40 p.m. It was preceded 11 seconds earlier by a 3.3 quake, and followed 3 minutes later by one registering 3.4.

No injuries were reported from Friday's quake.

The so-called "Mogul earthquake sequence" was named in reference to the neighborhood where hundreds of mostly minor earthquakes have occurred.

What's worth noting is that the size of the earthquakes has gradually grown larger, seismologists said.

They added that it's impossible to determine if the temblors are foreshocks of a bigger quake to come, or aftershocks of what has been.

Until April 15, quakes that could be felt above ground were occurring about once every third day, but on April 24, the first 4.2 quake was registered.

Since then, state geologist Jon Price said seismologists "were seeing 20 (of the magnitude) 2s and larger per day."

"This is an exceptionally vigorous sequence of earthquakes," Price said of the unexplainable sequence that has caused more than 500 recorded occurrences within the past week alone.

They are mostly shallow, occurring just beneath the surface to within a mile or two.

"Shallow makes us believe this is absolutely not volcanic," Price said.

Craig dePolo of the Nevada Bureau of Mines and Geology acknowledged the tension felt by residents of the area.

"What's going on is extraordinary," he agreed. "People are being needled by little earthquakes ... for months."

"And the best we can say is we don't know what going to happen."


On the Net:

UNR Seismological Laboratory

U.S. Geological Survey