PSN-L Email List Message

Subject: Re: What is an earthquake?
From: Brett Nordgren brett3nt@.............
Date: Sat, 19 May 2012 09:01:14 -0400


Hi Thomas,

I would think that they should count.  They are real quakes, 
releasing strain energy which has been building up over time.  It's 
just that they were artificially triggered well before they would 
have naturally occurred.  I think the best current opinion is that 
they are usually not triggered by the hydraulic fracturing operation 
itself but rather by the associated water-disposal wells which can 
serve to lubricate and weaken any nearby faults.

In mine blasting the vibration energy source is not geological but chemical.

Brett

At 05:21 PM 5/18/2012, you wrote:
>I wonder if anyone has an opinion on this subject or even cares. 
>Years ago, I was told not to post mine blasting. Now, a new era is 
>on us. Are we going to consider fracking/induced earthquakes as 
>earthquakes are treat them as if they were "human induced" like mine 
>blasts? Certainly not all the waveforms of a typical earthquake are 
>produced in these events. When the Arkansas earthquakes started I 
>faithfully posted those that were three and above. Now we know that 
>95% of those quakes were induced. A comment from the floor a week or 
>so ago (Menlo Park...USGS podcast) was accepted with qualification 
>when he said that chances are two mag 5 quakes already this year  in 
>the mid-continent region were induced. I suppose quakes in Texas, 
>New York State and the Washington, D.C. area are suspect too. And 
>then the latest one in Timpson, TX ... was that a real quake? How do 
>you suggest we separate the "real" from the "unreal"!


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