Tuesday, August 23, 2011
Virginia M5.9 Earthquake Mechanism
Looks like we have a fine mechanism here, totally unstudied. If we had decent instrumentation, we would find that it is similar to all the other eastern mechanisms, including Charleston and Toronto. You can find it buried in my posts somewhere.
Basically, as with the recent Arkansas attempt, there is a fluid mechanism, and these zones slowly grow from babies to full New Madrids. I only got this by merging rock mechanics and seismicity, which is something you'll never seen done elsewhere. But if you do a standard earthquake frequency plot, you can see that an M6 or greater has a very good chance. It has been somewhat unusual that we haven't seen them more often, but I believe that history has shown these to happen in clusters. There is good physics for this, since they are driven by fluids, and are very sensitive to distant earthquakes. We should expect a return to the 1800's when these were a dime a dozen.