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MCCALL,Idaho -- You could call it a mystery earthquake, a sonic boom, or maybe nothing at all.

Several witnesses report waking up to what they say was a small earthquake south of McCall early Thursday around 4:30 a.m. However, those shaky claims have employees at Idaho's U.S. Geological Survey scratching their heads in disbelief.

Mickey Hart lives five miles south of McCall just off Highway 55. The 50-year-old resident said she's experienced one previous earthquake here in the summer of 2001.

The second earthquake came early Thursday around 4:30 a.m. Hart says that's when her beloved border collie, Mr. Mac, detected the tremor before it hit.

It was four in the morning, and the house shook, Hart said. It woke up my husband and scared the crap out of my dog.

However, for some folks here in Idaho, those reports just don't seem to make sense.

U.S. Geological Survey Technical Information Specialist Tim Merrick said his agency's seismographs haven't shown any recent earthquake activity in Idaho.

If there was anything, it would almost certainly show up, Merrick said. Our seismology network across the United States is very sensitive.

Scott VanHoff, USGS Geospatial Mapping Coordinator, agrees.

Idaho looks amazingly quiet, and I don't see anything, VanHoff said, adding that the only earthquake he'd seen recorded was yesterday.

USGSrecords show that event was a magnitude 2.2 earthquake recorded around 9:30 p.m., at a location northwest of Weiser, Idaho.

However, other folks in the Valley County area maintain they positively did feel an earthquake early Thursday morning.

Captain Brandon Swain with the McCall Fire Department says he heard reports of the mystery earthquake from his brother, Clint Swain, who lives near Lake Fork.

My brother was awake at about 4:30 or 5 a.m., and the earthquake woke up his wife, Swain said.

A possible answer

Research geophysicist Joan Gomberg works for the USGS at the University of Washington in Seattle. Gomberg says her seismic records do, in fact, show something that could be a small earthquake, recorded at 4:42 a.m. MDT in the McCall area.

However, Gomberg went on to say that most earthquakes strong enough to be felt by people easily show up on USGS seismographs throughout the United States.

As to why some scientists and USGS employees can't readily see this one, Gomberg offered an interesting explanation.

This area is at the edge of the Pacific Northwest Seismic Network, and where the monitoring network begins to get sparser, so small earthquakes are more likely to be missed, Gomberg said.

Gomberg also reminds folks that sometimes a sonic boom from a nearby jet can feel like earthquake, along with large mining equipment, and road work.

However, Mickey Hart says she doesn't need a seismograph to tell her what she experienced was an earthquake. Instead, Hart says she trusts her border collie.

Mr. Mac knew right away. It really shook him up, Hart said.

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