Wednesday, August 24, 2011

Aftershocks define Virginia Earthquake


Ok, I am a bit happier with this earthquake.  It's right in the middle of the Central Virginia seismic zone, and probably fits right on the magnitude-frequency plot.  It's in the Precambrian basement, on a NE trending zone, just like Toronto.  It's a slightly strike-slip thrust fault with the directivity pulse going NE just like every other earthquake in the east.  The high PGV zone is entirely in the middle of nowhere, and Mineral may be on the footwall, although this is difficult to define with all the Appalachian garbage scrapped over the basement.  If you went on a hike in the woods over the 'punch' zone, you should see something.

Since this is just a single thrust fault, unlike thrust-shear system of New Madrid and Arkansas, we should only expect this one earthquake, ie. it won't have a twin.

If the geology is right, these zones should eventually evolve into a pure thrust and shear system, like New Madrid.

No comments: