Water well reacts to distant Chile earthquake

When Chile was rocked by a massive earthquake on Saturday, David L. Nelms knew Virginia would feel it, too - in water wells.

Sure enough, water in a monitoring well in Christiansburg, near Virginia Tech, rose at least 4 inches and then dropped about 2 feet as energy waves rippled through the Earth. But Nelms, a groundwater specialist at the U.S. Geological Survey in Richmond, saw something unexpected, too.

"The weird thing about this one was we saw it in wells we normally don't see response in," he said, looking over water level charts called hydrographs. "There's one out in Clarke County that we've never seen anything like this in, but there's a little blip up."

Wells in Augusta, Brunswick, Nottoway and Rockingham counties also rose and fell but not as much as the well in Christiansburg.

"There's always more of a response in Christiansburg," Nelms said. "Why that is, we don't really know."

The Christiansburg well is so sensitive to earthquakes around the world that the USGS has a Web site showing all the quakes it has responded to and by how much: va.water.usgs.gov/earthquakes/index.htm.

Coastal plains wells, because they are in sand, do not react to earthquakes. But wells in the Piedmont and mountains, where water flows through fractures in the rock, rise and fall as energy waves squeeze and relax the cracks.

The water level in the Christiansburg well is recorded every five minutes. The water likely rose more than 4 inches during the earthquake because it dropped farther than that, but it just wasn't recorded, Nelms said.

"This phenomenon happens other places," he said. "But the king daddy of them all is Christiansburg. For whatever reason, it's just responsive as all get-out."

Diane Tennant, (757) 446-2478, diane.tennant@pilotonline.com