Sunday, April 19, 2015

Frackonomics: The Earthquake Edition

For two years, I lived in Western Pennsylvania. I still own real estate there, and hope to sell it one day. So I'm very interested when questions pop up about the quality of life in Pittsburgh and its surrounding towns and boroughs. I also maintain ties with the business community, and sometimes that community will ask me environmental law questions.

I got one last week.

The amazing Joanne Quinn-Smith, publisher of Positively Pittsburgh Live, wanted to know about the earthquakes in Butler. "Why earthquakes?" I asked. She replied, "People are feeling earthquakes in Butler because of the fracking. I want you to find out about that." That got me interested enough to wake up this blog and start writing again.

This blog post is an introduction - a full discussion of this issue is too long for a blog. For good measure, I majored in English for a reason, so I'm not a geologist or a seismologist. Both of those specialties require a better knowledge of math. I am an environmental lawyer, and I'm pretty good at reviewing environmental impacts of a project. I can make the connections between an activity like hydraulic fracturing (fracking) and the environmental risks the activity poses. So, this series will review the risk of earthquakes related to fracking practices.

Let's get started with some background.

Earthquakes in Butler County?

Maybe. But probably not.

Pennsylvania has a historically low probability of earthquakes; they happen, but they're very, very rare. The U.S. Geological Survey (USGS), the federal agency that monitors such things, shows a very low probability that an earthquake would occur around western Pennsylvania. By contrast, my home state of Utah has a very high probability of earthquakes. California's risk is - famously - very, very high.

You can find this map here.
If you asked a geologist about the probability of earthquakes in Butler County, she would reply "probably not," and then add a bunch of extra information about probabilistic risk assessment, and that there is a history of earthquakes in the region. But the reality is that the possibility of a naturally occurring earthquake in western Pennsylvania is so low that we get beige on the USGS hazards map for the state. BEIGE.

You can find this map here.
Most of the earthquakes that occur in Western Pennsylvania are only felt by the most sensitive of instruments. We humans, being less sensitive than the machines in Pitt's geology lab, rarely feel earthquakes that measure less than 3 on the Richter Scale. These are called "felt" earthquakes.

The probability of naturally occurring felt earthquakes is so low that you could say "there is no risk of an earthquake in Butler County" and still show up a your amateur geologists meeting with head held high.

Notice how I slipped that lawyerly qualification into that last paragraph? Naturally occurring earthquakes are very rare. According to the USGS, there is such a thing as "induced seismicity." Activities like coal mining, blasting, and well-drilling practices can trigger "sleeping" faults under really specific circumstances.

Part II of this post will consider man-made, or "induced" earthquakes.

In the meantime, leave a comment below if you're from western PA and have felt a tremor.

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