Distant quakes could affect oil, gas fields: Study
12 July 2013
The powerful earthquake that rocked Japan in 2011 triggered tremors around a West Texas oil field, according to new research suggesting oil and gas drilling operations might make fault zones sensitive to shock waves from distant big quakes.
That large quakes could trigger minor jolts thousands of miles from the epicenter has long been known, and volcanically active spots like Yellowstone National Park often experienced shaking following a large distant event.
The influence of remote quakes on fault lines that had been weakened by human activity like the deep disposal of waste water at the Texas oil field had been known, however, a new study led by researchers at Columbia University and published today in the journal Science suggested a strong quake that struck halfway around the globe could cause minor to mid-size quakes near injection wells in the US heartland.
"The seismic waves act as the straw that breaks the camel's back, pushing the faults that last little bit toward an earthquake," lead researcher Nicholas van der Elst said in an email.
Scrutiny of quakes near industrial areas has increased in recent years with the ramping up of drilling to satisfy the US' energy hunger. According to research, wastewater disposal - the process of pumping fluids deep into the ground at high pressures could weaken nearby fault lines and even produce quakes big enough to be felt.
The controversial practice of hydraulic fracturing, or fracking, which used high-pressure mixtures of water, sand and chemicals for the extraction of natural gas or oil, could also trigger quakes, but these typically were microquakes - smaller than magnitude-2.
Van der Elst and his colleagues studied a set of injection wells near Prague, Oklahoma, among other sites and with the monitoring of changes in rock stress and sensitivity as small seismic waves from remote large earthquakes passed by, they concluded that sites with decades of injection history would more likely succumb to quakes.
According to the researchers it was a magnitude 8.8 quake in Chile in Feburary 2010 that triggered smaller quakes and tremors at the Oklahoma site in the days and months that followed. The same might be true of the 2011 Japanese and 2012 Sumatra earthquakes as also tremors around injection wells in western Texas and southern Colorado, the researchers maintain.
According to the researchers, at the core of the earthquake phenomenon, was the pressure that fluid injection put on rock in aquifers (pore pressure), which could lead to stress along fault lines.
''The fluids are driving the faults to their tipping point,'' explained study co-author Elst in a press release.