Members of the Kansas Geological Survey (KGS) were invited to NCK Tech in Beloit on Tuesday by Representative Susan Concannon to hold a forum discussing increased earthquake activity in NCK over the past couple of years.
Rolf Mandel of the KGS introduced Rick Miller who specializes in geophysics for the KGS at the University of Kansas. Miller said Earthquakes have been electronically monitored in Kansas since the mid-1970’s. The KGS operates 24 monitoring stations, including one in Jewell County. Between 1867 to 1976 there were 30 earthquakes felt in the state of Kansas ranging from 2.5 – 5.0 on the Richter Scale. Most quakes below a 2.5 will not be felt by humans. Prior to the 70’s, the magnitude of an earthquake had to be estimated by the recorded accounts of those who could feel them and their descriptions of how much anything moved.
Between 1977 and 1989, after electronic monitoring began, there were 171 recorded earthquakes ranging from 0.5 – 3.5 in magnitude in Kansas. There were just 18 quakes recorded from 1990 to 2014 ranging from 2.3 – 3.5. Activity has increased since then, particularly in South Central Kansas and sporadically in other parts of the state such as Jewell County in April of this year.
The year prior, there were several events in Smith County. The trend seemed to be that those quakes were moving to the east, and now into Republic County. The easterly locations are nearer to the Humboldt Fault which run north and south through the state close to a line near Manhattan where the largest earthquake in state history is believed to have taken place in the 1860’s.
Miller explained that he feels this is a natural cycle and not necessarily a “new normal.” After a peak in activity in Jewell County in April, the tendencies have fallen off significantly. Despite increased earthquake activity throughout the state, Kansas remains on the low end of vulnerability to experiencing damaging ones.
Jewell County is in what geologists refer to as the Salina Basin. Fault lines could be anywhere from ground level to miles deep within the earth. Miller said it’s like bending a board until it breaks. It’s most likely to break in the middle, and that’s where parts of Jewell County lie in the Salina Basin. Miller said there is less than a 1 percent possibility of a damaging earthquake hitting NCK. He explained how the possibility of having a damaging earthquake is estimated based on past activity.
Miller went on to explain the small size of fault lines in NCK would not likely allow for a higher magnitude quake than the max 3.5, or so, recorded in Jewell County in April. He said a magnitude 5 or 6, where any kind of significant damage could occur, are not possible based on the size of the existing faults in NCK.
Miller also said all of the earthquake activity in the state is happening at significant depth. He said there is no surface evidence of any known fault lines in Kansas having actually moved in recorded history. All the activity has been at depth and within small un-viewable fault lines. He said some of the activity, particularly in southern Kansas, that some believe are due to fracking are not.
He said fracking and the horizontal drilling that takes place itself does not cause earthquakes. What can and has contributed to earthquake activity is larger amounts water being injected deep into the ground in oil and gas exploration in general as compared to years past. He said water is injected into what is called the Arbuckle in Kansas which is similar to a sponge-like aquifer that already contained natural wastewater and is unfit for consumption due to natural causes aside from wastewater ejection. There are, however, some parts of the Arbuckle where water is potable in extreme eastern Kansas.
He said the issue with fracking is not the drilling itself which can increase earthquake activity. It is the increased amounts of water that are used and pumped deep into the ground in the production process which he believes has led to higher occurrences of minor earthquake activity in Kansas. He said the links to water injection and seismic activity are largely a product of where the work is being done and where the water is being pumped deep into the ground.
Areas in North Dakota, in comparison, have not seen any earthquake activity despite dramatic increases in fracking operations. More so than in Oklahoma and Kansas. It’s simply a difference in the ground composition. Water being pumped back into the ground in North Dakota is going into an aquifer enclosed on top and bottom by rock. While water being pumped into the Arbuckle in southern Kansas is surrounded by other types of ground composition and small faults. Yet, in Canada, there have been significantly more and stronger earthquake activity associated with water injection due to the fact that the water being pumped back into the ground is being done near existing fault lines.
Regulations have been created in Canada to limit how close water can be pumped into the ground near an existing fault line. Miller said no drilling or fracking in Kansas is close enough to any existing fault lines to be a concern.
After evidence was revealed showing that fluid injection was contributing to earthquake activity, the Kansas Corporation Commission required reductions in the amount of water that could be pumped back into the ground. After that, the number of quakes in Sumner and Harper Counties dropped dramatically according to Miller.
He said there has been a 50 percent reduction in quakes after the reduction order was issued. There was a two-year period between 2011 and 2013 where injections increased dramatically. After 2013 earthquake activity increased. After the order was issued in 2014, there was a year or so lag before activity began to decline and continues to do so.
He also explained the three types of earthquake activity. Foreshock, tremors before an actual earthquake. Mainshock, the actual earthquake itself, and aftershock. These three types of events are typically related, but they could occur anywhere from minutes to years apart.
The earthquakes in Jewell County are all but impossible to have occurred due to injection methods. No recorded earthquake has ever taken place within 15 miles of an injection point. The closest injection point to Jewell County is more than 45 miles away.
He said the small faults in Jewell County and surrounding areas are unlikely to produce an earthquake above a magnitude 4.0. He added that earthquakes in Smith, Jewell and Republic County have led scientists to believe that this is a natural, cyclical occurrence. There have been over 9,500 earthquakes recorded in southern Kansas since 2013, but the vast majority of those are not noticeable outside of seismometers.