Hi Thomas,

Good question... I am following the activity in the interior US with great
interest.

In Europe, it is easily to say whether an earthquake is natural or not. Over
here, the manmade quakes are of low magnitude and the epicenters are at well
known places (like quarries/mines or offshore detonations because of WWII
mines).

Some of the events in Texas, Oklahoma, Arkansas etc. are different. Those
events are much more intensive (magnitude and depth), I can even see some of
them over here in my data in The Netherlands (!)

This makes me wonder whether those events are induced ones or not.
Personally, I think it is too easy to blame fracking in all cases....


Regards,

Marchal van Lare
-Oostburg, The Netherlands

-----Oorspronkelijk bericht-----
Van: psnlist-request@.............. [mailto:psnlist-request@...............
Namens Thomas Dick
Verzonden: vrijdag 18 mei 2012 23:21
Aan: psnlist@..............
Onderwerp: What is an earthquake?

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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