Frequency of quakes at Honshu

Frequency of quakes at Honshu

RickardM 13 Mar 2011 01:05

So, most of you know that I have a slight and not so modest obsession over these darn quakes. The difference is that nowadays I don't automatically tie quakes to 2012, rather I have been able to accept that these things happen frequently as part of nature. As for this event, my thoughts go to all the people struggeling from the aftermaths of the big 8.9 quake (and ofcourse to all that lost their lives during this tragic event).

But, I have some questions that I hope someone will be able to answer; is strong quakes such as this always followed by this intense storm of aftershocks that we can se on the USGS site? As far as I can tell there's been between 10-15 M6-6.9 quakes/day since the big quake (as well as 40-ish M5-5.9 and quite a few 7's)? Was the amount of aftershocks as intense after the Chile quake last year? I know that plate tectonics is quite a mystery from time to time, but I was under the impression that quakes happen when enough stress is built up beneath (to really simplify things in absurdum) so wouldn't a big quake be the stress release and then just followed by a few aftershocks?

I'm sorry if I'm rambling on in my usual way here, but this thing confuses me quite a bit. Shouldn't the seismic activity slow down by now, or could "we" (those living along the ring of fire) be in for yet another big quake in the next couple of days?

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Facts are stubborn things.
- Ronald Reagan

Re: Frequency of quakes at Honshu

obaeyens 13 Mar 2011 01:46

Yes the aftershocks are expected and in this case still relative big but that is expected after such a big one.
It is basically the ground settling to a new equilibrium.

Big Earthquakes can always happen at any moment at the ring of fire. The one in Japan is now settling to equilibrium but Japan is only a tiny length compared to the rest of the ring of fire.

Re: Frequency of quakes at Honshu

RickardM 13 Mar 2011 18:51

Thank you for your response Obaeyens, I was actually thinking along those lines too. But, could this quake have created a new fault (like the New Madrid one) and therefore still is rather unstable (560 quakes and rising at USGS)? I mean, is it possible that it takes quite some time for this one to settle to equilibrium and thus might cause quakes in the area for quite some time?

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Facts are stubborn things.
- Ronald Reagan

Re: Frequency of quakes at Honshu

Astrogeek 15 Mar 2011 23:54

Hi Rickard;

There's no need to consider a new fault line, when the entire region is overlaying a fast-moving subduction zone. In fact, the Pacific plate is moving North-East at about 8.1 cm/yr, or a meter about every 12 years. It is the fastest moving plate on the Earth, as far as I know.

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"Do you ever think about things you do think about?" - Henry Drummond to Matthew Harrison Brady in Inherit the Wind