Interesting article in today's WSJ about lessons being learned from this week's Virginia earthquake that are of particular concern in safeguarding east coast nuclear reactors.
Especially noteworthy, to me, is the observation that east coast quakes' ground motion is "high frequency" while west coast quakes are a lower frequency and that the distinction has ramifications.
http://online.wsj.com/article/SB10001424...oWhatsNewsForthEarthquake Triggers Reactor-Design Review
Experts believe sensitive electrical equipment at North Anna responded to high-frequency ground motion—which is a hallmark of Eastern quakes, but not of Western ones—as if it were an electrical disturbance. Nine relays designed to protect expensive transformers from damage misread that cue, temporarily cutting off the plant from the electric grid, according to Dominion's Mr. Heacock.
Every earthquake produces a broad range of ground motion frequencies, expressed in "hertz" or cycles per second. But Western quakes are more noted for the lower frequencies that are especially damaging to large, rigid structures, such as buildings and bridges. Higher frequencies are more debilitating to finely tuned equipment such as electrical or electronic devices.
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