When I promised the amazing Joanne Quinn-Smith that I would look into the possibility of earthquakes in Butler County, PA, I had no idea that I would unleash powerful brainwaves into the Internet. Either that, or search algorithms are more powerful than I thought.
Why do I think this? For your consideration, I present the headline from Thursday's (4/23/15) Huffington Post.
And this, from the U.S. Geological Survey (USGS) on the
same day:
Actually, I am glad the USGS published its findings because it saves me from listening to the entire workshop. I was slogging through it when the report was released. I've found I can read a lot faster than other people talk, and with more patience.
The gist of this announcement is: for the first time ever, the USGS is recommending that emergency planning agencies consider the potential hazard to population and infrastructure from "induced seismicity."
That night, man-made earthquakes even made the lead story on the
Daily Show.
This post explores the possibility of man-made, or "induced" earthquakes.
WHAT?? Man-Made Earthquakes???
Man-made earthquakes aren't unheard of, so don't get too excited. Mining operations are common culprits.
But how can we assume earthquakes are man-made, and not an "Act of God?"
Warning: Science ahead (yinz can skip this if you want)
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| Tectonic Plates - geology.com |
Tectonic plates hold the answer (and a very generic one - go find a geologist if you want more detail). The earth's crust shifts along these plates; when it does, we get earthquakes and volcanoes. These plates are held in place by friction until the stress becomes strong enough to force the plates to shift and spring back.
(Let me help you visualize this: You want to get your friend's attention, but you don't want to yell, because you're in a math test and you want the answer to a story problem. You snap your fingers. Your thumb presses against your finger. It slips after some pressure, creating a shockwave of sound, disrupting class, and your teacher flunks you both for cheating. Your thumb is one tectonic plate, and your finger is another. The shockwave is the sound of the snap.)
Various weaknesses have formed in the earth's crust as a result of this stress; these are fault lines. The Rockies? A fault line. The volcanoes in Washington state? A fault line. The Appalachians? A very, very, very old fault line. I hope you get my (continental) drift.
The plate boundary closest to Pittsburgh is in the middle of the Atlantic Ocean - action along this plate will frequently light up Iceland and
mess up air travel in Europe. There's a volcano erupting in Chile
right now thanks to movement in the famous "Ring of Fire" around the Pacific Plate. Movement between the Eurasian Plate (green) and the Indian Plate (red) is responsible for a
7.9 magnitude earthquake in Nepal on April 25, 2015.
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| Earthquake Hazard in U.S. |
We expect, and plan for, earthquakes along and near tectonic plates. You can compare the location of high earthquake hazard (in red) in the U.S. with the location of the plate boundaries, if you want. The areas in the Western U.S. are red for a couple of reasons: (1) the Pacific Plate's eastern boundary snakes right up the West Coast, and (2) the population and transportation consequences could be devastating (and have been, historically).
Some locations in the middle of the country are faults resulting from mind-bogglingly old rifts (where tectonic plates tried to pull apart) that cause weaknesses in the earth's crust. Rifts make the surrounding crust more vulnerable to stress from plate movements, even when the boundaries appear far away. The likelihood of an earthquake occurring here is low, but the consequences/hazard is very high because of population and impacts to transportation.
Back to our regularly scheduled blog
Before I got all sciency, you were about to ask how we can assume earthquakes aren't an "Act of God."
Answer: Because plate tectonics tells us there shouldn't be earthquakes in Oklahoma or Ohio, we can take God out of the causal loop.
For example, in November 2011, a
5.6 magnitude earthquake (along with aftershocks) occurred about 50 miles north of Oklahoma City, Oklahoma, causing extensive property damage. Earthquakes had been on the rise in Oklahoma since 2009, and Oklahoma's Geologic Survey (OGS) was perplexed. The USGS took notice, too.
That purple blob on the left represents the Magnitude 3+ earthquakes recorded in 2014. The green blob shows magnitude 4+.
Then they put it another way. the red blobs on the right represent earthquakes occurring so far in 2015. Green blobs are those recorded in 2014.
No matter which way they looked at it, these things called non-tectonic earthquakes started happening with
alarming frequency:
During 2013, the OGS observed on average about 2, M3+ earthquakes each week on average, and this rate continued to increase during 2014. Currently, the OGS is reporting on average about 2½, M3+ earthquakes each day.
So, how did OGS and the USGS conclude these quakes aren't natural? As you can see above, the earthquakes in Oklahoma were spread out over a wide area.
For comparison,
here is the USGS Earthquake Report for Saturday, April 25 and Sunday April 26, 2015:
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The blob in Asia represents aftershocks from Saturday's Nepal Earthquake.
Contribute here if you can help. |
Notice how all but one of the earthquakes recorded on the right all occur on the tectonic boundaries? The pattern is generally linear.
The outlier is in Oklahoma.
When you have a seemingly random earthquake sequence, and you're trying to figure out if it will happen again, you have to figure out what caused it in the first place. So, that's what the agencies did. Almost 50 years ago, there was a string of unusual earthquakes in Colorado, near the Rocky Flats weapons arsenal. They were centered very near a deep (@3600') injection well. Experts concluded that the earthquakes were caused by the injection well: when use was discontinued, the earthquakes stopped.
Researchers at the USGS and the University of Oklahoma thought, "what if that is happening here?"
Marley's Ghost?
Okay. I need to be abundantly clear. Forgive me for harping on this, but I need to make this clear. As clear as Dickens had to be about Marley being dead. There is no story until you accept these truths:
- There are no tectonic plates near Oklahoma.
- There are fault lines deep underground.
- But there is no reason for them to produce random earthquakes.
- These faults are very deep, very old, and mostly dead.
Like Marley, however, they can be pressed into service if sufficiently provoked.
This is what happened in Oklahoma. According to one researcher, Dr. Elizabeth Cochran,
... what we looked at for the Oklahoma sequence was where the earthquakes occurred relative to these disposal wells. And we also looked at whether there was any link between changes in seismicity and changes in production or change in the volume of fluids being disposed of. And so what we found was that the earthquakes were occurring within very close proximity to the depth of these wells, within about 500 meters. And that's basically to the resolution we can accurately estimate the location of those earthquakes.
The deep injection wells in Oklahoma were actually pressing down on these old fault lines:
... if you look in detail at the injection pressures, what happened was initially they could inject wastewater without any pressure. It would just basically go straight down the well, and they didn't have to put any pressure to make it go into the formation. But those pressures gradually rose over the 20 year period until essentially they'd have to keep increasing the pressure at which they'd force the water down in order to continue injecting the same volume of water.
And so we think that was showing that essentially this formation, which had been previously drilled and produced and now is being reinjected into, was essentially filling up, that it was a closed space where they were pumping a lot of water down into, and essentially it got to the point where the formation was full, and that caused increases in core pressure, which may have led to these events along the existing fault systems there.
The entirety of her interview is available
here. The
conclusion is that the Oklahoma earthquakes are the result of "injection/disposal of water associated with oil and gas production."
Yes, Virginia, there are man-made earthquakes. Next post, whether there can be earthquakes in Butler County.
(c) Tamar Cerafici, all rights reserved. This blog may be reposted with all of the following information.
Legal Shoe's author is Tamar Cerafici.
Tamar is an internationally recognized leader and legal specialist in the often complex and challenging nuclear regulatory industry. As an environmental attorney she has been at the forefront of the industry in building regulatory and policy framework for a new generation of nuclear plants.She is a major contributor to the first Early Site Permit granted under 10 CFR part 52, successfully implementing alternative site analyses that has become the general standard.
She is also an internationally known expert on marketing techniques for lawyers and other billable-hour professionals, speaking around the world to delighted audiences everywhere.
Find this blog at http://legalshoe.blog spot.com
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