The 4.8 magnitude earthquake that hit East Texas back in 2012 was the result of wastewater injections from oil and gas companies. These are the findings, say scientists using a new method of research in the earthquake/geophysics field—Interferometric Synthetic Aperture Radar (InSAR).
InSAR is a "technique for mapping ground deformation using radar images of the Earth's surface that are collected from orbiting satellites," according to the U.S. Geological Survey. It's regularly used to monitor volcanoes. In East Texas, it could detect changes in the of Earth's surface at the scale of centimeters.
Setting InSAR's eye on four high-volume wells used for wastewater disposal, the researchers began to track the changes in the Earth. Wastewater injection wells handle a byproduct of fracking, which study co-author William Ellsworth compares to "ancient ocean water" in that it is "too salty and too contaminated with other chemicals to treat economically, so the only viable solution at present is to put it back underground." The wells then push that wastewater thousands of feet underground, although distances vary per well.
Other scientists have already hypothesized, using more traditional analysis, the same solutions to the East Texas earthquake events. As many people here have pointed out, in virtually every diary I’ve written on this subject, wastewater injection by itself is not the problem. Neither is hydraulic fracturing, necessarily. The issue is where the wastewater gets injected.
The InSAR measurements revealed that wastewater injection at the shallow wells resulted in detectable ground uplift up to 5 miles (8 kilometers) away but only a modest rise in pore pressure, which is the pressure of fluids within the fractures and cavities of rocks, at the depth at which earthquakes happen 2 or more miles below the surface.
Increasing pore pressure within a geologic fault can cause the two sides of the fault to slip and release seismic energy as an earthquake.
According to the study’s findings, the shallow well sites seemed able to distribute the pressure of wastewater injection in such a way as to not travel down towards the “crystalline basement, a deep and faulted rock layer where earthquakes originate.” However, the deep well injection sites helped build and create the pressure that ended with the 2012 earthquake and subsequent tremors.
The scientists involved feel that what’s most important about their research is that they feel this method of research (geological mapping from space) can help the oil and gas industry make safer decisions about how they build and operate their waste well facilities.