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Aftershock vs separate quake

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When can an aftershock be considered a new earthquake? Fox news is reporting the March 28/29th quake in Indonesia as an aftershock of the December 26th quake in 2004. I would think that after three months a new tremor in the same area would no longer be considered an aftershock.

Aftershocks can continue for many years after a large earthquake. However, the magnitude of the aftershocks drops quickly with time. I don't think it's clear as of this writing whether the March 28/29 quake is an aftershock or a new main shock. It is certainly related to the December quake, though. Gwimpey 03:31, Mar 29, 2005 (UTC)

I think this really comes down to a definition of aftershock. I put "earthquake aftershock" into Google and the best definition contained two criteria namely "in the same area" and "is usually a magnitude smaller". I updated the article to include "in the same region" in the definition. The earthquake mentioned above does not meet either criterion. It was nothing the same real estate being 150 km southeast of the 2004 earthquake and its aftershock region and in the range of 2-4 times smaller based on the final magnitude of the 2004 earthquake being 9.0 or 9.3. This Caltech article mentions the earthquake or aftershook issue but doesn't give a definitive answer.

I addressed some of the above in my additions but it must be remembered that the idea of what an aftershock is is defined by its fit to an emperical relation (Omori's law). Some people think that aftershock actually follow an exponential decay, based of a model and that the n(t) can be fit just as well (with no data at very small or large times you can really tell they apart). Others suggest almost all events are aftershocks and that a finite (but small) chance exists that any event will be followed by another that is larger than itself so a foreshock is really just a large aftershock. Bumfluff 20:56, 7 September 2005 (UTC).[reply]

Haiti 2010

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Bit puzzled about this one. According to http://www.iris.edu/seismon/zoom/events/?lon=-72.61&lat=18.45 there have been 36 aftershocks after the 7.0, all round and about the 4.8 to 5 magnitude.

If the distribution law is to hold, that implies several hundred more before the magnitude fades out. That's a bit worrying.--Brunnian (talk) 21:26, 13 January 2010 (UTC)[reply]

Omori's Law

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Instead of stating that the formula has no physical basis/meaning (because in an earthquake, there has to be some physical basis), shouldn't it say it has no predictive value? That is to say, it is a formula that is fitted to somewhat random observational data, but cannot be used to predict when the next aftershock will occur? --71.245.164.83 (talk) 00:50, 24 February 2011 (UTC)[reply]

It actually says that the parameters derived from the empirical data (p and c) "have no physical basis/meaning". Mikenorton (talk) 07:44, 24 February 2011 (UTC)[reply]


In the discussion of Omori's Law, the top refers to the frequency or rate of aftershocks; while the bottom paragraphs, explaining the rate on the n-th day after the main shock, use the word "odds". But odds has a special meaning (probability for / probability against), while frequency is (probability for / (probability for + probability against)). This conflict in language should be resolved: use "rate". Rcyeh (talk) 05:00, 25 January 2012 (UTC)[reply]

I've changed 'odds' to 'probability', as that is what is being described. Omori's law is used routinely to estimate the probability of aftershocks. I'll try to find a good source for that. Mikenorton (talk) 07:13, 25 January 2012 (UTC)[reply]
I've added a source - note that it uses exactly the original wording. Mikenorton (talk) 08:02, 25 January 2012 (UTC)[reply]

This entire section is neither illustrative nor informative for the nonspecialist reader, instead jumping straight to a technical statement of observed laws. That’s fine for a textbook, but this is not a textbook. This piece of science communication could benefit greatly from being rewritten to suit an encyclopaedia. Inopinatus (talk) 09:20, 15 February 2023 (UTC)[reply]

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