08-25-2014, 12:50 PM
(08-24-2014, 09:10 AM)Randy B_imp Wrote: I heard on the news that the Loma Prieta quake was 22 times more powerful....wow.
Yeah it's pretty wild to think of it that way but it kind of makes sense since magnitude is on a log scale... the Loma Prieta is listed as 6.9 while this one is 6.0 which means about one order of magnitude difference.
That's not the whole story though, as the depth of the epicenter also makes a difference. So what we really should care about is "intensity" instead of magnitude, because that measures the actual force felt at any given point on the ground.
Deeper epicenter means the power is dissipated over a larger area by the time the waves hit the surface. I'd want to imagine that it should be inversely proportional to the square of the depth, if you think of power dissipation in the absolute simplest way possible, but earthquakes can't be quite that simple. Pretending that it is that simple, than an earthquake of the exact same magnitude but twice the depth would have 1/4 the intensity.
So assuming 22 times more power and half the depth, we get about 4/22 times as much intensity.
"The More You Know..."
And, I did not wake up for this one. I didn't know it happened until I peeked at Bay Area Riders Forum and somebody posed the question, what happens if there's an earthquake while you're riding?