The Edmond Sun
Hydraulic “fracking” is not the cause of recent earthquakes felt in the Edmond area, but a possible connection to Arcadia Lake is being studied, a report states.
Monday morning, Oklahoma Geological Survey seismologist Austin Holland said the agency is investigating the possible link to the lake with the U.S. Army Corps of Engineers, which partnered with the City of Edmond to build it; the lake opened in 1987.
Holland said discerning the cause of the spike in activity, which began Nov. 2 and continued with a 2.8 magnitude quake recorded just south of the lake during the weekend, will take time. Detective work related to the possible lake connection will include the geological makeup of the area, Holland said.
The likelihood of a link to the lake is low, but the public is interested in learning the cause, and a cause other than natural geological changes may never be found, Holland said. Each earthquake causes changes in sub-surface conditions, he said.
At one point in early June, the lake was 10.5 feet above normal after storms caused flashflooding in the metro area.
The Oklahoma Geological Survey will be placing more seismic stations across the state in an effort to cover more areas, Holland said. A number of stations already have been in place in central Oklahoma. Temporary stations have been provided by the U.S. Geological Survey.
In an analysis of the recent activity, Holland and colleagues Amie Gibson and Christopher Toth stated there are no salt-water deposit wells within several miles of the recent quakes. Furthermore, there were no hydraulic fracturing operations in the area, indicating it is not a possible cause either, the document stated.
“The correlation between lake levels at Arcadia Lake and this earthquake swarm is interesting and requires futher investigation,” the authors stated. “Earthquakes can be caused by high lake levels or rapidly changing lake levels, and there often (are) time-delays between these surface observations and earthquakes occurring at depth.”
In late 2011, increased seismic activity began south of Arcadia Lake and remained fairly constant until October 2013, according to the report. On Nov. 2, a significant number of magnitude 3.0 and greater earthquakes began occurring. They were felt in significant portions of the northwest metro area, Edmond and surrounding areas.
Primarily a flood control body of water, Arcadia Lake has 1,820 surface acres and 26 miles of shoreline, according to the city. The lake serves as a recreation area and as a flood control for the Deep Fork River Basin.
Additionally, the authors of the study stated it is possible the spate of recent quakes are a northwest extension of the Jones earthquake swarm.
“This sequence is quite comparable to previous periods of activity within the Jones earthquake swarm,” the authors of the report released last week stated.
One such similar period occurred between Jones and Luther in August and September 2010, the authors stated.
Ultimately, earthquakes are due to the natural accumulation of stress or pressure on faults, the authors stated. Occasionally, human activity or hydrological loads can slightly alter pressures on faults.
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