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FORTH WORTH (CBSDFW.COM/AP) — Thursday’s 4.0 magnitude quake near Johnson County has reinvigorated the fracking debate; the Texas Railroad Commission is requiring operators of five disposal wells to perform a series of tests.

Bosque Disposal Systems LLC, EOG Resources Inc., MetroSaltwater Disposal Inc. and Pinnergy Ltd have agreed to shut down the wells temporarily until results are in on the tests, which will be made within days. The testing will help determine the effect of wastewater injection into subsurface rock formations in the areas feeling the recent activity.

A 2.7 magnitude quake hit Dallas Saturday:

Epicenter of Saturday's quake.

Epicenter of Saturday’s quake.

Thursday’s quake was the largest to ever hit Texas. Prior to 2008, there was only one tremor registered in the Fort Worth area. In January, nine quakes in less than 24 hours were been registered by the USGS in Irving.

Thursday’s quake was centered approximately 30 miles southwest of Dallas. It is the fifth in a week.

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