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A short class with Sarah and her students. The other ways are under More.
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Today, we're going to talk about deep well injection. Does anyone know what that involves?
Is it about putting waste into deep holes in the ground?
Exactly! Deep well injection involves disposing of fluids deep underground. This can change pore pressure and stress in the Earth's crust. Can anyone guess why this might cause earthquakes?
Maybe the pressure buildup could make rocks break?
That's correct! When the pore pressure increases enough, it can cause existing faults to slip, leading to tremors. Remember the acronym DWI for Deep Well Injection to help you recall this process. Let's move on to a real-world example.
Were there any cases where this caused big earthquakes?
Yes, in Oklahoma, there was a marked increase in seismicity due to fracking and injection. This shows the impact of human activities on natural systems. Can anyone think of other examples?
What about places where they mine?
Great thought! Mining activities can also induce seismicity. Let's save that for our next session!
Now let's talk about hydraulic fracturing, commonly known as fracking. Who can explain what fracking is?
It's when they pump fluid into rocks to make them crack for oil or gas, right?
Exactly! While it helps extract resources, it can lead to unintended larger seismic events, especially if not done carefully. What do we expect to see in terms of seismic activity during fracking?
I remember you said microseismicity is normal!
Yes! Microseismicity, or small quakes, occur regularly. But, improper control can lead to significant quakes. Can anyone think of a location where this has happened?
I think there were issues in Ohio related to that.
Excellent example! Always keep in mind the concept of pressure and how it relates to fault activity. Understanding these consequences is key for engineers working in seismic areas.
Now, let's discuss mining and quarrying. Why might these activities create small earthquakes?
Maybe because they blast rocks and dig deep?
That's right! Blasting operations can lead to minor seismic events as the stress in the Earth changes. Over time, what other effects might this have?
They might change how stress is distributed underground?
Exactly! Changes in stress fields can trigger seismic activity, even long after mining has stopped. It's an important consideration in planning, isn't it?
Yeah, engineers have to account for that!
Great! So remember that mining adds to induced seismicity. Let's wrap up what we discussed today.
Finally, let's explore geothermal and oil extraction. How might these practices induce seismicity?
They take fluids out, which can make the ground sink or change pressure?
Exactly! Extracting fluids can lead to voids underground and raise the risk of fault reactivation. What does this mean for areas around extraction sites?
There might be a higher risk of earthquakes occurring?
Yes! Understanding these risks is essential when designing infrastructure. Always consider the environmental impacts of resource extraction. Let's summarize what we learned today about human-induced seismicity.
Seismic events caused by human activities.
A method that alters pore pressure and may trigger earthquakes.
A resource extraction method that can lead to minor and major seismic activity.
Small quakes anticipated during activities like fracking.
Practices that can disrupt subsurface structures leading to seismic events.
Fracking cracks with pressure high, but too much can make the earth sigh.
Once, there was a town that used deep wells for waste. Over time, they felt quakes — little at first, but then they shook awake. The community learned that their actions could cause the ground to quake.
RAMP for remembering: (R)esources, (A)ctivities, (M)ining, (P)ressure.
DWI: Deep Well Injection impacting seismicity.
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What is induced seismicity?
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Define hydraulic fracturing.
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What is deep well injection?
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Earthquakes that are directly caused by human activities.
The disposal of fluids into deep geological formations, affecting pore pressure and stress.
A method of extracting hydrocarbons involving high-pressure fluid injection to fracture rocks.
Small seismic events that occur, often associated with fracking and other industrial activities.
The process of extracting heat or hot water from the earth for energy production.
This section explains how human activities, particularly industrial practices, contribute to induced seismicity through mechanisms such as deep well injection, hydraulic fracturing, and mining.
The section delves into various human-induced activities that can lead to seismic events, particularly focusing on deep well injection of fluids, hydraulic fracturing or fracking, mining operations, and geothermal or oil extraction. Each activity alters subsurface conditions and can trigger seismic events ranging from small tremors to larger earthquakes.