BAYOU CORNE — U.S. Geological Survey seismological recordings from a station near the northern Assumption Parish community of Bayou Corne show a series of earthquakes occurred on June 8 and July 3, a University of Memphis researcher said Thursday.
Stephen Horton, a research scientist with the university’s Center for Earthquake Research and Information, said about a dozen seismic events have been detected from generally, though not exactly, the same area. The USGS station picking up the quakes is in White Castle, about five miles from Bayou Corne.
“They (USGS researchers) looked at the data, and they see what appear to be long-period seismic events. They are earthquakes, in that an earthquake really just means that the earth shakes. So, yes, the earth is shaking,” he told a crowd of several dozen residents, reporters and officials gathered during a rainy outdoor community meeting near the Bayou Corne boat launch off La. 70 South.
His statement is the first formal indication that seismo-meters have recorded what residents in the area have said they have been feeling for more than a month: tremors putting out candles, knocking pictures askew and cracking slabs and wallboard.
Horton said he set up on Thursday the first of four seismic stations in the area to try to pinpoint where the quakes are coming from and how deep they are in the ground.
“And by associating that with whatever is down there, then we can hopefully come to some conclusion about what is the cause,” he said.
In a later interview, Horton said the first station was established at the Texas Brine Co. LLC facility in the Bayou Corne area.
He told the gathered residents his group is planning on as much as a four-month experiment to do the measurements.
The quakes have appeared to coincide with the accelerated release of natural gas from the surfaces of Bayou Corne and Grand Bayou.
The gas releases have prompted parish, Louisiana Department of Natural Resources and other state officials to try to determine the source.
John Boudreaux, director of the parish Office of Homeland Security and Emergency Preparedness, said a series of tests on the oil and gas infrastructure and brine operations in the dome have not determined the source of the gas.
The latest such test — on a salt dome cavern owned by Chevron Pipeline that stores natural gas — is close to the bayous but appears not to be a source of the gas, officials said.
“So we are at a point where the source is still unknown,” Boudreaux said.
He said USGS, DNR and the Louisiana Department of Environmental Quality have been asked for additional help.
The uncertain origin of the releases has raised community worries about the pace of official response and what may be happening to the Napoleonville Dome, which starts one mile southeast of Bayou Corne and has two caverns that hold natural gas.
On Wednesday, Assumption Parish Police Jury President Martin “Marty” Triche said he is trying to have a meeting with DNR officials and legislators to increase the agency’s involvement and suggested it has taken too long for DNR to respond.
But in interviews Thursday, DNR officials defended their response, saying they immediately reacted when they were informed about the gas releases.
“The first we heard about it was June 11,” said Joseph “Joe” Ball Jr., director of the DNR Injection and Mining Division.
DNR inspectors, for instance, have checked abandoned wells as a possible source of leaks to no avail and reviewed the tests on the Chevron salt dome cavern.
During the community meeting, Bayou Corne resident Carla Alleman, 50, asked Horton directly if the gas bubbles are connected to the earthquakes. Horton said that was an excellent question but said he did not yet have an answer.
“It’s possible … they may be related. They may not be related. We don’t know yet, OK. It could go either way, and that’s one of things we want to determine,” Horton said.
He also said officials at the University of Memphis center, which works on contract with USGS, decided to place the seismometers in the Bayou Corne area because that is where residents have reported feeling the tremors.
He said the White Castle station is too far away and, on its own, cannot detect where the tremors are originating. Horton said at least three stations are needed in the area to triangulate the location.
When asked, Horton said the magnitude of the quakes detected so far cannot be calculated until their location is pinpointed, but he suggested they are likely between a 2.5 and 4.0 on the Richter magnitude scale.
According to the USGS Web site, the Richter scale has no upper limit, but the largest earthquakes recorded have been at the 8.0 level.
Horton said a 2.5 is about the minimum required for someone to feel an earthquake.
Early reports from parish officials indicated that USGS was not picking up the tremors being reported by residents.
Horton said USGS records seismic activity but likely would not locate earthquakes less than a 3.0. He added USGS likely could not have located the earthquakes anyway because only one monitor was detecting them.
“And so they (USGS officials) would not have known about it other than people calling in,” Horton said.