An interesting question that gets into an interesting issue. We always explain the difference between east & west coast quakes in terms of difference in how seismic waves travel in the two regions 1/ https://twitter.com/NotNormalIndstr/status/1292502102296600577

But there's another factor as well: not every earthquake of the same magnitude generates the same amount of shaking 2/

Wait, what, isn't magnitude a measure of energy release. In fact no, not exactly: modern magnitude values reflect how big the fault patch was that moved, and how far it slipped 3/

Radiated energy, which controls shaking, depends on the details of fault motion. And it turns out that, magnitude unit for magnitude unit, quakes in the east pack a bigger punch than quakes in the west 4/

Seismologists talk about a difference in "stress drop," which we usually don't try to explain 'cause magnitude is confusing enough all by itself 5/

Anyway, if today's #ncearthquake indeed packed less of a punch than a typical M5.1 in the east, that may be related to the (apparently) shallow depth of the earthquake 6/

This one is going to be interesting to analyze 7/7