Weatherford Democrat

December 29, 2013

QUAKE CENTRAL

Monitoring data defines area between Briar, Reno ground zero of earthquakes

Taylor Armerding
CNHI News Service

• 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.

Ellsworth said the earthquakes are shallow, occurring at an estimated 2.5 to 4 miles below the surface of the ground.

Though the depths are somewhat uncertain due to a lack of detailed information about the area geology, that is something that can be remedied, he wrote.

SMU researchers are relocating several of the NetQuakes instruments to better surround the source region of the earthquakes, he said.

Meanwhile, Texas Railroad Commissioner David Porter is expected to discuss the issue with the public this week. A town hall meeting is scheduled for 5-7 p.m. Thursday at the Azle High School Auditorium, located at 1200 Boyd Road in Azle. Other state and local officials are expected to be in attendance.

With some experts saying the earthquakes could be occurring as a result of injection wells in the area, many have called on the Texas Railroad Commission, which regulates the oil and gas industry in Texas, to investigate whether the earthquakes have been triggered by activity in the area.

RRC Chairman Barry Smitherman told the Democrat earlier this month the commission will likely also ask a group with the qualifications and experience to do a study of the issue. 

Meanwhile, researchers attempting to narrow down the location of the earthquake epicenters are making headway.