Scientists baffled by unusual swarm of hundreds of quakes off Oregon coast wrote:By Jeff Barnard, The Associated Press

GRANTS PASS, Ore. - Scientists listening to underwater microphones have detected an unusual swarm of earthquakes off central Oregon, something that often happens before a volcanic eruption - except there are no 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 320 kilometres 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.

The hydrophones are left over from a network the U.S. Navy used to listen for submarines during the Cold War. They routinely detect passing ships, earthquakes on the ocean bottom and whales calling to one another.

Scientists hope to send out an OSU research ship to take water samples, looking for evidence that sediment has been stirred up and chemicals that would indicate magma is moving up through the Juan de Fuca Plate, Dziak said.

The quakes have not followed the typical pattern of a major shock followed by a series of diminishing aftershocks, and few have been strong enough to be felt on shore.

The Earth's crust is made up of plates that rest on molten rock, which are rubbing together. When the molten rock, or magma, erupts through the crust, it creates volcanoes.

That can happen in the middle of a plate. When the plates lurch against each other, they create earthquakes along the edges.

In this case, the Juan de Fuca Plate is a small piece of crust being crushed between the Pacific Plate and North America, Dziak said.

Quakes confuse experts, send kids under their desks wrote:CNN) -- Experts are mystified by what they call a "swarm" of earthquakes hitting Reno, Nevada.

Quakes aren't uncommon there, but analysts just do not know what has caused 344 of them in the area in the past week, the strongest of which was magnitude 4.7.

The quakes have prompted schools to teach more emergency drills, while seismologists examine the data for clues.

No one fault line has been identified as the culprit and the pattern of the earthquakes also has scientists saying they are confused.

Typically, several small aftershocks follow a larger quake. In this case, several smaller temblors led to a larger one, which caused minor damage to shops and homes. Watch damage from Friday's earthquake »

"Whether this last one is the final one of that building pattern is the question, and it will only be answered with time," said Tom Rennie, a seismic analyst with the Nevada Seismological Laboratory. See a map of where the earthquakes hit »

At Jesse Beck Elementary School in Reno, Nevada, there have been three earthquake drills in the past month, prompted by the string of quakes that began in February.

"By the third drill, they pretty much have it down," Kristen Brown, principal at Beck Elementary, said with a laugh. "We make noises over the intercom, sort of a 'mock earthquake,' and had the kids do the duck, cover and hold method."

Aaron Kenneston, Washoe County emergency manager in Nevada, said reaction from the public has been mixed.

"There are a variety of reactions, just like there are a variety of personality types," said Kenneston. "It ranges from people who used to live in seismic zones like California who don't think it's a big deal, to some people like the elderly or frail who are very concerned."

Nevada is the third most active state for earthquakes after California and Alaska.

Since earthquakes cannot be predicted, Kenneston said the most important thing he's focused on is public education.

"There's confidence that comes with preparation, and my goal is to get the populace familiar with how to protect themselves."

Kenneston advises the public to take precautions, like moving heavier objects closer to the floor and securing bookcases and shelves. During an earthquake, people should take cover under a table, near an interior wall or in a doorframe.

At Beck Elementary, education is also a priority.

"One of our sixth-grade teachers has made earthquakes a unit of study for science. Now the kids know more about earthquakes than me," said Brown. "You definitely have to be prepared, and I feel we are."