Sumatra Quake Caused Water
In VA Well To Rise 3 Feet
By A. J. Hostetler
Times-Dispatch Staff Writer
Spawned by the South Asian earthquake, seismic waves rolling deep within the Earth made Virginia well water rise and fall by 3 feet, the U.S. Geological Survey reported.
Strong oscillations at a 450-foot-deep well near the Round Meadow Country Club in Christiansburg in western Virginia started about an hour after the magnitude 9 quake struck some 9,600 miles away. Seismic waves travel through the Earth at about 7,400 mph.
"It took another five hours for that sloshing to settle out," USGS groundwater specialist David Nelms said yesterday. "That water's going up and down, up and down, up and down in that well."
The height of the oscillation came about 77 minutes after the earthquake struck near Sumatra. The water level rose about 2 feet, according to Nelms. Data indicate that water came at least within 4 inches of the surface, perhaps even spilling out.
"We saw it here. That's what amazes me, we saw it here," Nelms said. "In about an hour, we were seeing something from that earthquake here."
The well is one of 280 whose groundwater levels are monitored by the USGS and the Virginia Department of Environmental Quality and one of about a dozen with satellite equipment that provide daily readings. The 2002 drought revealed the value of such timely information as residents across the state wanted to know why their wells ran dry, Nelms said.
The equipment at Christiansburg records groundwater readings once every 15 minutes, so the oscillation may have been even greater, Nelms said.
Data is transmitted from the well to the satellite and eventually to the USGS in Richmond, allowing DEQ and USGS personnel to check readings by computer.
The earthquake data is considered a "bonus" to the wells' usual job monitoring groundwater. The Dec. 26 quake is the first time the DEQ-USGS well project recorded the effect of an earthquake and had it online in near real-time, Nelms said.
Nelms was on vacation when he heard news reports about the underwater earthquake that sent tsunamis throughout the Indian Ocean.
"I wondered if we saw it. I went on the Internet from home and saw it," Nelms said of the spike recorded at the Christiansburg well. "As soon as that pops up on the screen, you go, 'I know what that is.'"
The Christiansburg well is known to respond to earthquakes around the world. When the 1985 Mexico City earthquake struck, with a magnitude of 8, the well recorded a 7-foot oscillation, according to Eugene Powell of the DEQ office in Charlottesville.
Nelms said he was surprised that the earthquake's effects were recorded so clearly, because of the 15-minute recording intervals.
"We were kind of afraid that maybe [the equipment] would miss it if it all happened so quick, but the duration of this tremor was such that we got some good readings," Powell said.
Officials at the Richmond USGS office are now discussing whether the equipment on wells should be altered to record more frequently when oscillations are greater than expected.
The Christiansburg well, taken over by the DEQ in 1969, is finished in limestone. Water enters the well through fractures or cracks in the rock. Like fireplace bellows, seismic waves compress and expand the fractures, drawing water in and expelling it.
"We mainly see this, the earthquake effects, in wells west of [Interstate] 95 in rock country," Nelms said. Those wells are measured in real time. Monitoring of Virginia's more numerous coastal wells focuses on the water table, which typically doesn't show earthquake-related changes.
The well just west of Christiansburg is the only one in Virginia known to have rocked with the South Asian earthquake, although a Roanoke well dropped a bit around the time of the earthquake, Nelms said.
A well in Augusta County reputed to respond to earthquakes lacks real-time satellite equipment and is not scheduled to be checked manually until February, Powell said.



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