Tuesday 24 December 2013

Two Magnitude 3.3 Earthquakes in Parker County, Texas.

The United States Geological Survey recorded a Magnitude 3.3 Earthquake at a depth of 5 km, in northeastern Parker County, Texas, roughly 30 km to the northwest of Forth Worth, slightly after 11.30 am local time (slightly after 5.30 pm GMT) on Sunday 22 December 2013. This was followed by a second quake with the same Magnitude, at a depth of 6.5 km and roughly 1 km to the north, slightly after 7.10 am local time (slightly after 1.10 pm GMT) on Monday 23 December. There are no reports of any damage or casualties relating to these events, though both were felt throughout the Fort Worth and Dallas areas.

The approximate locations of the 22 & 23 December 2013 Parker County Earthquakes. Google Maps.

Northern Texas has suffered a string of Earthquakes over the last two months, which some residents have linked to injection well drilling, (pumping liquids into oil or gas bearing rocks to displace the hydrocarbons and make it easier to extract), a process that has been linked to increased seismic activity in parts of the US and Europe. The Railroad Commission of Texas, which has responsibility for regulating the oil and gas industries in Texas, and pointing out that many of these quakes have occurred in areas where injection well drilling does not occur.

Northern Texas is affected by seismic activity on the Balcones, Mexia, Talco and Meers Fault systems, although not all of the recent quakes have been close to any of these structures, and any increase in seismic activity is likely to be viewed with concern by people living in the area. Several observers have noted that the much of the recent activity has been associated with the Barnett Shale, which underlies the Dallas and Fort Worth area, and which has become a focus for the natural gas industry in recent years. The Barnett Shale is considered to be a 'tight' reservoir (i.e. it does not give up its gas easily) and has largely been worked by the hydraulic fracturing (fracking) method, a form of injection well drilling that involves blasting liquids into a hydrocarbon-bearing formation at high pressure in order to break up the rock structures and release the gas, a process which has caused particular concern to environmentalists, who link the methodology not only to Earthquakes, but also to pollution of aquifers and excess use of water (a major concern in dry areas such as Texas).

The Texas Railroad Commissioner, David Porter, is to address a public meeting on the subject at Azle High School in Azle, in Tarrant County, Texas, at 5.00-7.00 pm on 2 January 2014, where local residents are likely to raise concerns. The Mayor of Azle, Alan Brundrett, has asked the commission to look specifically into the causes of Earthquakes affecting the town.

Witness accounts of quakes can help geologists to understand these events and the rock structures that cause them. If you felt these quakes (or if you were in the area but did not, which is also useful information) you can report it to the USGS here (for the 22 December event) or here (for the 23 December event).

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