re: #110 reine.de.tout

Wow.
According to that there was some movement, very slight, but some movement along the Gulf Coast? I didn’t feel anything. Why doesn’t it show anything in the areas where the quake was felt? Am I not understanding how to look at this?

It’s a matter of where the sensor array is placed. Those sensors have a sensitivity of 22 millionths of a meter, or about 900 millionths of an inch (rounding, 1/1000th of an inch) basically two orders of magnitude below what any human could possibly feel. So while the sensors are going off like strobe lights, it’s highly unlikely to be felt by anyone living over the plastic soils of Baton Rouge. Or Kansas, Iowa, Nebraska, &c.

It *does* give credence, however, to the hypothesis that the rupture was within the granitic core of the Blue Ridge, as opposed to a growth or other fault in the soils/rock of the Piedmont. If it was in rock to the east of the Blue Ridge, the granitic core would have absorbed it. Since the sensors indicated a radiating shock wave to the west, it is indicative of a rupture in the granite core itself, which would propagate both east and west.

In addition, since the core of the Appalachians is a contiguous granite mass from Georgia to Maine, it would have caused the entire pluton to ring like a bell, causing shock waves along that SW->NE axis to radiate east and west and be felt from Atlanta to Toronto. Which, for a classically trained structural geologist (Yo!), is absolutely wicked cool.

By the way, if there is a 5.8 in LA, you don’t feel it in Portland. The west has been so faulted and shattered for so long that fault blocks don’t have that transmission capability. No connectivity of relatively incompressible rock facies.

Sorry to go tangential to the thread, but like Faber College, I believe that Knowledge Is Good.