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Arthur T Knackerbracket has found the following story:
In Oklahoma, reducing the amount of saltwater (highly brackish water produced during oil and gas recovery) pumped into the ground seems to be decreasing the number of small fluid-triggered earthquakes. But a new study shows why it wasn't enough to ease bigger earthquakes. The study, led by Ryan M. Pollyea of Virginia Tech in Blacksburg, Virginia, was published online ahead of print in Geology this week.
Starting around 2009, saltwater disposal (SWD) volume began increasing dramatically as unconventional oil and gas production increased rapidly throughout Oklahoma. As a result, the number of magnitude 3-plus earthquakes rattling the state has jumped from about one per year before 2011 to more than 900 in 2015. "Fluids are basically lubricating existing faults," Pollyea explains. Oklahoma is now the most seismically active state in the lower 48 United States.
Previous studies linked Oklahoma SWD wells and seismic activity in time. Instead, Pollyea and colleagues studied that correlation in space, analyzing earthquake epicenters and SWD well locations. The team focused on the Arbuckle Group, a porous geologic formation in north-central Oklahoma used extensively for saltwater disposal. The earthquakes originate in the basement rock directly below the Arbuckle, at a depth of 4 to 8 kilometers.
The correlation was clear: "When we plotted the average annual well locations and earthquake epicenters, they moved together in space," says Pollyea. The researchers also found that SWD volume and earthquake occurrence are spatially correlated up to 125 km. That's the distance within which there seems to be a connection between injection volume, fluid movement, and earthquake occurrence.
(Score: 1) by rylyeh on Wednesday January 10 2018, @06:47AM (7 children)
"a vast crenulate shell wherein rode the grey and awful form of primal Nodens, Lord of the Great Abyss."
(Score: 3, Interesting) by Anonymous Coward on Wednesday January 10 2018, @07:05AM (6 children)
Given how each 1.0 on the scale is a factor of 32, what would you prefer in a span of 500 years?
1 earthquake of magnitude 9, with mountains collapsing and a tsunami that spans the Pacific
32 earthquakes of magnitude 8, pretty devastating once every 15 years
1024 earthquakes of magnitude 7, twice yearly but not really a big deal for a country with building codes
32768 earthquakes of magnitude 6, an annoyance every 5 days
1048576 earthquakes of magnitude 5, just a rumble you get used to every few hours
33554432 earthquakes of magnitude 4, indistinguishable from passing trucks
1073741824 earthquakes of magnitude 3, not that you could tell
If you like that last one better than the first one, frack more.
(Score: 2) by FatPhil on Wednesday January 10 2018, @07:09AM (3 children)
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 4, Informative) by takyon on Wednesday January 10 2018, @07:19AM (1 child)
https://en.wikipedia.org/wiki/Moment_magnitude_scale [wikipedia.org]
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by FatPhil on Wednesday January 10 2018, @07:40AM
However, you have to remember that they've taken into consideration the *area* affected by the quake to get that number. Bigger quakes affect a bigger area, so the energy per unit area does not scale quite as aggressively as that 32x implies, and the local damage is better correlated to the energy per unit area. Hence amplitude is still an important measure.
However^2, the calculation you're performing does rely on total energy dissipation, so it is the correct unit to use.
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 1) by khallow on Wednesday January 10 2018, @04:56PM
Energy goes up as 10^1.5 (which is almost a factor of 32) per one delta. It's the motion that goes up by a factor of 10. The interesting thing is that the power law seems to apply well to the frequency of earthquakes, which decline by similar amounts as one increases in the magnitude scale. Stuck faults tend to decline in frequency by a factor of 10, while slippery faults (and the Oklahoma situation) tend to decline as a factor of 30. That has the consequence that large earthquakes are far more likely on stuck faults than on slippery ones and far larger numbers of small earthquakes happen on the slippery faults.
The real news here is that earthquake frequency in Oklahoma has declined dramatically over the past couple of years. That indicates to me that the real problem is not lubrication of existing faults as claimed in the story, but the energy input from pumping pressured water underground.
(Score: 2) by PartTimeZombie on Wednesday January 10 2018, @11:28PM (1 child)
The Christchurch Earthquake of February 2011 was 6.7 and killed 185 people.
We have building codes (they have been strengthened however) but I can't see anyone wanting to go through that every week.
From what friends tell me, the worst part of the many, many aftershocks (some of which were 4.0 - 5.5 ) was the unrelenting nature of them, many people left the city because they couldn't stand it any more.
I don't think any earthquake of 5 - 6 could possibly be just an annoyance.
(Score: 0) by Anonymous Coward on Thursday January 11 2018, @02:33AM
If they'd had repeated earthquakes of magnitude 6.7, there would not have been 185 deaths each time. The deaths per earthquake would rapidly drop, even if the population is kept up. Bad buildings fail, and are replaced by good buildings. People learn not to stack heavy things on flimsy shelves.