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Aftershocks - A Misinterpretation (03-28-2005)
note: this was originally written March 28, 2005. I re-edited it on June 8, 2008.
I was once watching CNN's coverage of the March 28, 2005 Indian Ocean earthquake...and I cringed every time they mentioned that it was an aftershock of the Dec 26, 2004 earthquake. The concept of "aftershocks" is one of the great modern inaccuracies of geology. And it bothers me to no end that geologists continue to not clear this matter up.
Let me say, very strongly, that there is no way an 8.6+ earthquake is an aftershock to a 9.0+ quake event FROM 3 MONTHS EARLIER! It is bad science. It is bad thinking. It leads to mistakes in what actually happens in reality.
There are definitely "aftershock" earthquakes. I'm not trying to eliminate them from the geologic dictionary. However, those are usually brought about due to hyper-stressing the immediate surrounding area of a ruptured fault segment after an earthquake. This then causes small faults in that hyper-stressed area to rupture. These events are usually very small in magnitude and very abundant.
The March 28, 2005 earthquake was a completely different beast. It was more likely an "earthquake induced earthquake". Or what other scientists call an SSE ("Second Strong Earthquake"). A very controversial theory still.
The correct concept is this: the Dec 26th even shifted a large amount of stress onto another portion of the same fault line (it also shifted stress onto other, adjacent fault lines as well...which is why you will sometimes have completely different faults rupturing in high magnitude events within a short time period). The amount of shifted stress was enough to bring the other fault segment very close to rupture, but not enough to rupture it immediately. Rather, after a few more months of stress buildup it finally reached it's current stress threshold...and ruptured.
Sorry sports fans, but that isn't an aftershock. Indeed, a major reason the March '05 event occurred was due to the Dec 26th event. But the terminology is all wrong in describing it. It's just two major earthquake events occurring very close in proximity and time. But if you think about it, the picture starts to become clearer and you start to realize just how much stress transfer causes one earthquake after another. Let me say again from earlier "It is bad science. It is bad thinking. It leads to mistakes in what actually happens in reality." We shouldn't be looking at earthquakes as individual, isolated events. They need to be seen on a grander scale. One event transferring stress and causing another event, which transfers stress and causes still other events. So on and so on and so on........
Come on geologists! Open your mind and throw away these ancient, wrong ideas! Let aftershocks be aftershocks and let true earthquakes be just that. Start connecting the dots and broadening our scope of the stress/strain state of our world! Afterall, you aren't going to advance science or thought if you continue to hold onto incorrect ideas and misapplied terms.
This Rant Brought To You By Matthew T. Chernay
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