The Chilean Earthquake was huge. An 8.8 on the Richter scale. That means it had 100 times the shaking amplitude of the Northridge Quake.
This works because of the logarithmic nature of the Richter Scale. It’s in base ten. In simple terms that means each increase of 1.0 is a tenfold increase. And in Richter terms that means a tenfold increase in shaking amplitude. Lots of people interpret this as power, and while the two are closely related, the amplitude and power aren’t 1:1. In fact, as the difference on the Richter Scale increases, the power varies even more than the amplitude.
Lots of the info out there says that Richter was measuring the power of the quakes, but the best info says he was measuring wave amplitude. This was what he could observe. And observe he did: the scale was born (not surprisingly) in Southern California.
Measuring wave amplitude means that the actual ‘power’ (in the Physics sense, not the everyday sense) varies by a 3/2 exponent (or you could say ‘to the 3/2 power’ but that’s the mathematical use of ‘power’, not the physics use, or the everyday use. Silly mathematicians.) Okay, what this all means is that a 2.0 increase in the Richter Scale for shaking amplitude means a 1000-fold increase in the power of the quake (in the physics sense). Yeah, yeah, if you really wanna know, get your pencil out and get your math on – it works.
What this all comes down to is this – the Chile earthquake was a big ass quake. It made Northridge (6.7) and Haiti (7.0) look like they weren’t even trying.
Apparently enough mass shifted from the quake that the earth literally moved on its axis. (No, that wasn’t you. That was the quake.) It moved a whopping 8 centimeters (that’s about three inches, for the conversion impaired.) 8 centimeters is a big movement in earth terms. Think about how hard it is just to move your refrigerator 8cm, then think about doing that to the earth. In earthquake terms again, Haiti and Northridge didn’t touch this.
This movement of the axis has apparently altered sunrise time, popping it up to about five minutes earlier. And that’s not all. Not only did the quake tip the axis, it moved enough of the earth’s mass toward the equator to make the earth spin just a little faster. If you doubt or don’t know how centralizing mass makes things spin faster, try spinning on a tire swing or a rope. Go ahead, relive some childhood memories in the name of science. You can also run your own biology experiment here . . . fast spinning induces nausea due to the way your eyes track movement. Good times!
Sadly, though the earth is spinning faster, it isn’t noticeable. (Even if it were largely different, would we notice it? After all, the vast majority of our timescale is based on the rotation of the earth . . . so how would we know?? It’s all very Einsteinian.) While it’s cool that the Chile Quake changed the course of days, it only shortened them by 1.26 microseconds. What a let down!
In fact, the Indian Ocean Quake (that triggered the Tsunami in 2004) moved enough mass to shorten earth’s days by 7 whole microseconds. Cool, but still not measurable without some very precise instruments.
This does mean that since 2004 we have lost a total of 8.26 microseconds from each day. Let’s consider one more thing, though: both these quakes moved mass toward the equator, and quakes tend to move in the same direction. This is because the earth is, quake by quake, moving further and further away from the good old days of Pangaea. So it makes sense that these big quakes will continue to shorten days.
Sadly, we won’t be here to see it really take effect. It either won’t add up to enough time in the time we have, or we’ll perish in one of the big quakes that really moves the mass around. Ironically, wanting to see the days get shorter, is detrimental to living to see them get shorter.
I really wanted to say to my great-grandchildren, “I remember when days used to be a full two minutes longer than what you kids have!” On the upside, just the time it takes your neurons to fire to learn that the days have gotten shorter was way more than the 8+ microseconds we’ve lost. In fact, we could argue that, with all the time we put into contemplating the Chilean Earthquake just now, we have effectively lost a good second+ per day for the next year! Mission Accomplished! Sweet!
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