The earthquake and tsunami ravaged region of northern Japan suffered its worst aftershock since the March 11 quake, when a 7.4 magnitude aftershock hit just offshore. Buildings as far away as Tokyo shook for more than a minute, and a tsunami warning has been issued for a wave up to six feet high.
Although power outages have occurred in Fukushima and Yamagata, Kyodo News service is reporting no new “abnormalities” at any of the region’s nuclear power facilities.
To be clear: the Richter scale is logarithmic. Every 1.0 magnitude difference represents a tenfold increase in the amplitude of the waves measured by seismographs. In energy terms, a 1.0 magnitude difference represents roughly a 31.6-fold increase, or, to put it most simply, an increase of 0.2 represents a doubling of energy released.
WHAT THIS MEANS is that since this earthquake had a magnitude 1.6 lower than the 9.0 last month, it released roughly 2^8 = 256 times less energy.
Whether you want to take this as reassurance that a 7.4 magnitude earthquake isn’t that bad (uh, it is pretty bad) or as demonstrative of how fucking huge that 9.0 was (It fucking was) is up to you.
Pirate video stream of live Japanese TV news here: http://www.ustream.tv/channel/kamori
Hmph. You’d think a know-it-all like Ben would know that they no longer use the Richter scale.
@1
To be clear.
1) The richter scale can not be measured for an earthquake in Japan because it is based on the instrument response for a type of seismometer of which no functioning example exists, and calibrated for events located in California.
2) The moment magnitude scale has a factor of three in the log formula, so each unit of magnitude is a factor of 30.
You should get you shit right next time you are trying to sound smart.
@4: Sorry for trying to help.
That’s a lie, I’m not sorry for trying to help, and you being a shit isn’t going to stop me from trying to help in the future. Thanks for not really helping, though!
@4 addendum: I looked into it further, and you’re wrong anyway. The moment magnitude scale is still log10, not log30, so each unit is still a tenfold increase in the base measurement. What does increase at roughly thirty-fold is the energy released, which is what I said in the first place (more accurately, it increases by 10^(3/2) ≈ 31.623 for each unit of magnitude).
Oh my god you’re dumb.
What do you think is increasing if not ‘the energy’ (ie seismic moment). Look back at the wikipedia article you just read and try a little experiment. Try plugging in 8 and 9 for magnitude in to the first equation there; solve for the moment. Tell me what’s increasing by ≈30 fold. Okay. Now what there is increasing 10 fold. (Hint: Nothing, because you’re an idiot).
Asparagus, thank you for making me laugh my ass off.
@8: Huh. Welp, never claimed logarithms were my strong suit. I guess now I know.
To clarify, we use the shindo scale in Japan. I never really paid much attention to it at first since it seemed so unscientific. It measures ‘shaking’ (but yes, there’s a formula behind it), so — as with last night — it can be a shindo level 6+ in Miyagi ken but a level 3 in Tokyo to. It turns out this is a great way to describe what people are actually experiencing, since obviously a 7.1 doesn’t feel like a 7.1 across the entire country. Makes sense when you have a lot of them.