Wednesday, April 15, 2015

Oklahoma earthquake - extremely tiny and shallow

They are now reporting earthquakes below 2.5.  I guess they got their extra seismic analyst.  We are now going for a record for the tiniest earthquake being felt.  The rule of thumb used to be that you needed a 3 to be felt, but OK is going way beyond that.  This is an extremely shallow strike-slip (shear) earthquake, you can tell by the felt area to the NE.  Their stated depths don't mean anything.  Now, I really wish they had calibrated broadband seismometers so we could tell the PGV.  My general experience Ontario is that it takes 0.5 mm/s to be felt.  But I suspect that everybody is constantly on tenterhooks here, so that the sensitivity must be a lot lower, counteracted by the general apathy to report yet another one.  :)

Update:  Two high-three thrusts, giving an intensity 5, right on the main shear zone.  In Chaos, anything can happen.  :)

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