On the morning of September 3rd, 2016, the residents of Oklahoma (as well as many neighboring states) were literally shaken out of their beds when a
5.6, 5.8 magnitude earthquake stuck close to the small town of Pawnee.
USGS Event Page: M5.8 – 15km NW of Pawnee, Oklahoma
This is the helicorder feed from Clayton, Oklahoma on that morning just after the quake. Note, the lines are off the scale due to the proximity of the recording station which is roughly 155 miles to the Southeast of Pawnee.
Below is a capture from a station located in South Carolina. It took about 6 minutes for the Earth motion to reach the East Coast.
24 hours after the time of the event there are aftershocks showing up
Closer Look at the Epicenter
For those not familiar with the seismic activity of Oklahoma, we have weak to mild earthquakes occurring nearly every day. These range in from 2 to 3 in magnitude and are only felt by those living in close to the epicenters. When Oklahoma experiences 4+ magnitude quakes those are typically picked up and reported by local media and usually cause a stir on social media sites.
According to this map provided by Oklahoma University there is a large network of faults spread out across the state of Oklahoma. This is the first map I’ve seen showing this much detail. They range from the minor, more shallow faults down to the deeper, subsurface faults.
Using an overlay on the map above, this image below shows the edge of Osage county and the location of the epicenter of the main quake and some of the aftershocks.
Note how the epicenter and following aftershocks are positioned in-between two shallow depth (3,000 – 4,999′) subsurface faults indicated on the larger map.
When the coordinates for the epicenter is keyed into Google Maps a well site shows up less than a mile away from the epicenter.
Here’s a closer look at the well site using Google Earth. I’m assuming it’s a Class II injection well based on the tire tracks circling around the site as if water trucks have been in and out over time.
It can be confirmed this is a fairly new site by looking back through the historical satellite imagery. This well was not present before 2014. I imagine the residents of the home located across the road from this location received a fairly rude awaking at 7 am along with everyone else in the region.
I’m not saying the disposal well caused the earthquake, but it’s worth noting the surface activity around the area. The epicenter for most of the earthquakes in the central Oklahoma area are down in the 5 kilometer range. Way below the base of the deepest hydraulic fracturing or injection well activity. However, there are smaller and more shallow faults located in this range.
Injection wells are nothing new. They have been used by the oil and gas industry in Oklahoma since the practice of drilling for resources first started. The earliest record I could locate of well sites date back to the 1930s.
It’s a bit unsettling (no pun intended) when you look at just how many injection wells there are across the state.
With all of this fluid being pumped down into the Earth, it begs the question of how stable the ground remains under this pressure.
There is another theory on the cause of these earthquakes relating to solar activity and Earth’s electromagnetic field. I will cover that information on my next post.
USGS upgrades Pawnee earthquake to 5.8 magnitude