AUSTIN -- Thursday’s magnitude 4.8 earthquake made for a lot of chatter on Twitter and Facebook.
The earthquake was centered near Peggy, Texas, or about 47 miles south-southeast of San Antonio. According to the USGS, people from as far south as Corpus Christi and Kingsville felt a weak to light shake, and as far north as San Marcos, Austin, Burnet, Round Rock, and Georgetown.
Click here for Texas' history of earthquakes from the USGS.
Although small, this earthquake goes down in the record books as the strongest in history for that part of Texas. In 1993, a magnitude 4.3 earthquake shook the same area. Experts say these two quakes are most likely due to the exploration and extraction of natural gas. Although the act of drilling does not induce earthquakes, the extraction, or pumping of fluids at oil and gas fields can.
Thursday’s rare event had many people wondering if South-Central Texas could have an earthquake’s epicenter in our area. The answer is yes, although very rare. A book entitled “Texas Earthquakes” by Cliff Frohlich and Scott D. Davis provides excellent information of two earthquakes in the Austin area. One occurred in January 1887, and the other in October 1902.
On October 9, 1902, an estimated magnitude 3.9 earthquake shook Austin. The epicenter was in southern Travis County, near the community of Creedmoor. Frohlich & Davis provide a piece of a report published in the “Austin Daily Statesman” of some people thinking Round Mountain or Pilot Knob where “in a state of eruption” as they were on the lookout for “molten lava.” Also in the book is a piece from the “San Antonio Express,” where a farmer in Cedar Creek concluded the shaking was caused by a meteor hitting Pilot Knob.
Another earthquake was reported on January 5, 1887. The estimated magnitude 4.1 quake was centered in eastern Bastrop County near the community of Paige. People in Austin, Bastrop, Elgin, and Giddings all reported the shake. No major damage was reported.
Frohlich and Davis mention that neither quake can be blamed on petroleum production/exploration since oil was not discovered in this part of the state until 1912. Instead, a series of faults are likely the culprit. The “Ouachita Belt” stretches from Arkansas and Oklahoma, southward into Texas and Mexico. The series of faults that make up the Ouachita are: the Mexia-Talco, the Balcones, the Charlotte-Jourdanton, and the Luling (Frohlich and Davis).
The 1902 earthquake in Southern Travis County was likely associated with the Balcones Fault, while the 1887 quake in Bastrop County was most likely linked to the Mexia-Talco system (Frohlich and Davis). None of the local faults are very active right now. About 10 million years ago, the Balcones Fault was very active, but will likely remain inactive.
So other than a little shake now and then, South-Central Texans can rest easy from the threat of damaging earthquakes.
If you would like more information of the history of Earthquakes in the Lone Star State, pick up “Texas Earthquakes” by Cliff Frohlich and Scott D Davis, ISBN: 0-292-72551-5.
Click here to see a seismic hazard map.
Click here to see the seismicity of Texas.