• Town hall meeting on area’s ground shakes Thursday at Azle High School
By CHRISTIN COYNE
A letter sent last week to Azle Mayor Alan Brundrett from the U.S. Geological Survey provided new information about where the area’s quakes have been originating.
The USGS has been working with a team from Southern Methodist University to identify the area where the earthquakes are starting, according to a letter written by Dr. William Ellsworth of the USGS Earthquake Science Center, who said information collected from residents in the area on the USGS website suggested the earthquake activity might not be as broadly distributed as implied by the imprecise USGS National Earthquake Information Center data.
Earthquake epicenters in Texas routinely determined by NEIC can be uncertain by 5 miles or more due to the great distances between seismograph stations, according to Ellsworth. The closest station used by the NEIC to locate the Azle earthquake is more than 60 miles to the south, he added.
After the ice storm in December, SMU researchers installed five “NetQuakes” seismographs from the USGS in the area around Azle, Sanctuary, Reno, Briar and Pelican Bay, which became operational on Dec. 15.
“Since then, I have located a number of earthquakes, including several that were also located by NEIC,” Ellsworth wrote. “The epicenters are confined to a limited area approximately midway between Reno and Briar. This source zone includes the epicenters of the two magnitude 3.3 earthquakes of Dec. 22 and 23.”
Ellsworth said the earthquakes are shallow, occurring at an estimated 2.5 to 4 miles below the surface of the ground.
The USGS has recorded at least two dozen earthquakes in the area ranging between 2.2 and 3.7 in magnitude over the course of the past two months. Across the region, some 30 earthquakes have been recorded since Nov. 1, including some in Palo Pinto County north of Mineral Wells.