Oklahoma Hit By Its Strongest-Ever Recorded Quake

First time accepted submitter Wheelie_boy writes "No word yet on hell freezing over, but Oklahoma experienced a 5.6 magnitude earthquake early Sunday morning. This is the largest quake ever recorded in the state. Only minor damage and no casualties have been reported."

Re:Wow

[Lakitu]

http://www.springerlink.com/content/u315626k2071q0j0/ [springerlink.com]

Abstract
In China, the earthquakes induced by water injection have occurred in four oil fields including the Renqiu oil field, and in two mines. Production of oil from the Renqiu oil field began in 1975 and the injection of water into the oil field commenced in July 1976. The induced earthquakes have been occurring in the area for the past 17 years, since December 1976. The controlled experiments of water injection showed the cause and effect relation between water injection and earthquakes. Source parameters such as source dimension, seismic moment and stress drop of a large number of the induced earthquakes, andQ factor for the area have been determined. The results indicate that the stress drop varies from 0.2 to 3.0 bar and theQ factor has an average value of 75.0. The low-stress drop and lowQ factor values imply that the earthquakes are caused by the brittle fracture of weak rocks under low ambient stresses, due to a decrease in their strength because of the injection of water. The induced earthquakes are unevenly distributed in the oil field. The northern part of the oil field, where the reservoir rocks are characterized by low porosity and low permeability, exhibits high seismic activity with the largest earthquake registering a magnitude of 4.5 and about 68% of the total number of induced earthquakes in this part. Whereas, the southern part of the oil field with higher porosity and higher permeability is characterized by low seismic activity with the largest earthquake registering a magnitude of 2.5 and only 4% of the total number of earthquakes which occurred in this part. These features of the focal region suggest that larger earthquakes may not occur in the Renqiu oil field area.

Re:Wow

[Anonymous Coward]

My dad worked in the industry for years and years through KS, OK and TX. He went on many many frack jobs that, in my memory, go back to at least the mid '70's. Please do not link an earthquake today to an active frack job just next door. Or in the case of the San Antonio "second ever recorded" to the active project. I know it is easy to link the two in your mind but these jobs have been happening for decades without an increase of seismic activity so just realize sometimes it can just be circumstantial connection.

Re:Wow

[gstrickler]

Wrong. OK has a history of M5+ quakes about avery 60 years. 1887, 1952 and now 2011.

Re:Wow

[j. andrew rogers]

Because we don't get earthquakes in this part of the world. Ever.

Not according to the USGS seismic hazard maps. Unlike most other states, Oklahoma even has a separate map dedicated to that state. See:

http://earthquake.usgs.gov/hazards/products/conterminous/2008/maps/

There are many states that are prone to periodic earthquakes. This includes many states that most people just assume do not have earthquakes because they are infrequent. I would be hesitant to assume attribution to a fracking that which can be adequately explained by previously known geological science.