The blast was apparently amplified for miles by weather conditions and led many people across the county to fear an earthquake or another gas line explosion.

Dave Vande Linde, chief of the state Department of Environmental Protection Office of Explosives and Blasting, believes the sound came from a blast set off as part of normal mining operations at Kingston Industries LLC's Rush Creek No. 2 Mine south of Charleston.

Vande Linde said inspectors are continuing to investigate, but believe that they have narrowed the incident to a 5:08 p.m. blast at the 375-acre surface mine.

He said the blast in question did not violate any DEP standards, but was very close to exceeding the sound limit of 133 decibels measured at any buildings or structures. For instance, DEP inspectors found the blast measured 125 decibels at a monitor on a gas well about 1,000 feet away and 131 decibels on a monitor at a cemetery about 2,200 feet away, Vande Linde said.

Mine operators use explosives -- usually ammonium nitrate and diesel fuel -- to blast off hilltops, removing rock and earth to reach coal reserves underneath.

The cloudy and wet weather contributed to helping to spread noise from the "airblast," which is energy from the blasting released into the atmosphere in the form of air pressure, he said.

"It can really make a shot run down the hollow," Vande Linde said. "It was really the worst time to set off a shot."

But, Vande Linde said, DEP regulations don't take into account the potential for weather conditions to make sound carry more than it might otherwise.

"The blaster is supposed to use their best professional judgment on that," he said.

Barney Frazier looked at the Kingston Mine from his home along Mount Alpha Road on Tuesday. He said he frequently takes photos of dust rising from mine blasts nearby. Although he's sensitized to the sound and feeling, Frazier said Tuesday's blast startled him.

"It not unusual for a blast to go off. You can hear it and feel it in our home," Frazier said. "But that was the loudest blast I've ever heard with the most dust and the most vibration."

Frazier and other residents along the Mount Alpha Road area turned out in 2005 to oppose a permit for the mine's operation, saying they were concerned about blasting, noise, dust and other problems.

Since then, Frazier said the operation and the blasting has gotten closer to his house.

DEP officials installed a seismograph in Frazier's front yard based on the proximity to the Kingston Mine late last year. He said DEP inspectors showed up Wednesday morning to download a seismic reading. They drove straight to the mine after reading the report, he said.

Vande Linde said a blast of this size is not especially unusual in a coal-mining community.

"I don't see how this was any different than any other [coal-mining blast] out there," he said. "It's not an uncommon thing."

Michael Hohn, state geologist and director of the West Virginia Geological Survey, said Tuesday's blast was not big enough to register seismic waves at the station in Morgantown. Large mine blasts, he said, sometimes register as seismic activity and geologists then work to distinguish them from an actual earthquake.

Coalfield residents frequently complain about blasting, and government officials often downplay those complaints.

The U.S. Office of Surface Mining concluded a decade ago, for example, that additional regulations on blasting were not needed, despite the growth of the practice as mountaintop removal mines got larger.

More recently, government scientists have been examining whether predicate matter deposited in coal-mining communities from blasting could be part of the explanation for increased risk of illnesses found among residents living near mountaintop removal mines.

Reach Ken Ward at kw...@wvgazette.com or 304-348-1702. Reach Travis Crum at travis.c...@wvgazette.com or 304-348-5163.