Satellite-based radar confirms man-made Texas earthquakes

Herman Weaver
September 23, 2016

"The detection of uplift when combined with well-injection records provides a new way to study wastewater injection", Ellsworth said.

While the East Texas temblor and several strong aftershocks were suspected to be "induced" by the nearby wells, "our research is the first to provide an answer to the questions of why some wastewater injection causes earthquakes, where it starts and why it stops", said study co-author William Ellsworth, a geophysics professor at Stanford University's School of Earth, Energy & Environmental Sciences.

A series of earthquakes struck near the town of Timpson in eastern Texas over the course of a year and a half, with the team of American and British researchers looking into the most powerful of them, which took place in 2012 and reached a magnitude of 4.8.

For the first time, scientists say they have proof that some Texas earthquakes are man made.

The study, published in the journal Science, suggests that the researchers could estimate how much pressure is increasing underground due wastewater injection.

These wells had operated between 2005 and 2007, injecting about 200 million gallons of wastewater annually underground at its peak-or, as Science pointed out, "about an Olympic swimming pool's worth of wastewater pumped underground each day".

Brackish water naturally coexists with oil and gas within the Earth.

The theory of pore pressure has been used to conclude that the Texas quake was due to human activities.The pressure is created beneath the earth's surface due to pores clogged by waste waters, which eventually results in sudden tremors.

Injecting wastewater at a depth of over 1 mile, or 1.6 kilometer, two of the wastewater disposal wells the researchers examined lie directly above where the quake occurred; and the other two wells injected similar volumes of wastewater, but at shallower depths, just over a half mile, or 800 meters, below the surface. The researchers explained that continued seismic activities in these areas were caused by the pore pressure continuing to diffuse throughout the area from earlier injections. The scientists believe that satellites may improve forecasts of the man-made earthquakes.

But where that wastewater is injected can make a huge difference.

This did not happen at the shallow well sites in East Texas because a thick layer of almost impermeable rock beneath the injection sites of the shallow wells prevented the pore pressure from migrating downward towards the crystalline basement, a deep and faulted rock layer where earthquakes originate.

As explained in the Stanford press release, the rising pore pressure built up until it triggered earthquakes in 2012 along an ancient fault line. The researchers affirmed that natural disaster which rocked Texas in 2012 was due to the deformed surface by waste waters dumped in the area near Timpson.

"So now the goal, the scope of every scientist across the United States of America, and maybe overseas, is to make that injection safer" by "reducing the number of earthquakes as much as we can", he said. "Injecting at shallower depth above a blocking formation would reduce the ability of the pore pressures to migrate to the basement and activate the faults".

"This research opens new possibilities for the operation of wastewater disposal wells in ways that could reduce quake hazards", Shirzaei said.

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