New, peer-reviewed research conducted by scientists at the US Geological Survey provides additional evidence of a direct connection between wastewater disposal and earthquakes.
The paper, to be published in the November/December issue of Seismological Research Letters (SRL), focuses on the strongest earthquake ever recorded in Kansas -- a 4.9 magnitude quake in November 2014 near Milan, which is in south-central Kansas.
The earthquake, felt as far south as Fort Worth and as far north as Omaha, occurred along the Nemaha fault system, which runs from Nebraska to central Oklahoma. Still, this is an area which, prior to 2014, had no significant history of seismicity.
The authors report that, in the vicinity of Harper and Sumner counties, which encompass the region where the Milan temblor and related fore- and aftershocks occurred, only two earthquakes (both with Mw 2.7) were reported by the USGS for the period of 1964 to 2010.
The area's apparent lack of seismicity was a thing of the past by 2014, when, over the next two years, there were 374 Mw >2.5 earthquakes in the two counties. What's more, the scientists write, "the onset of seismicity started soon after the initiation of injection of large volumes of wastewater."
According to data provided by the Kansas Corporation Commission, wastewater injection in the area began to increase in 2010, when 19 million barrels of wastewater were injected. By 2013, the amount had jumped to 61 million barrels, but that was only the beginning. Records show a fourfold increase in wastewater injection volumes in 2014 over 2013 levels.
The record Mw 4.9 quake happened on November 12, 2014.
The authors of the paper point out numerous similarities between the circumstances surrounding this earthquake and those that have been researched in Oklahoma.
One of the similarities, they say, involves the proximity of the injection points to the crystalline basement, through which the faults run; they write: "The depths of the wastewater injection wells in the Milan region typically bottom out at depths of 1.3-1.7 km, placing the injection within a few hundred meters of, if not on or into, the basement. The observation that the earthquake depths are deeper than the depths of wells is consistent with suspected induced earthquakes in Oklahoma where wells inject into the Arbuckle formation, and induced earthquakes are in the basement."
The earthquake caused minor damage; reports included instances of cracked plaster, items thrown from shelves, and structural damage to some buildings constructed of unreinforced masonry, according to the study.