Aftershock Totally Explained

Everything about Aftershock totally explained

:This article is about the geological event. For other uses of the term see Aftershock (disambiguation). An aftershock is an earthquake that occurs after a previous earthquake (the main shock). An aftershock is in the same region of the main shock but is always of smaller magnitude strength. If an aftershock is larger than the main shock, the aftershock is redesignated as the main shock and the original main shock is redesignated as a foreshock. Aftershocks are smaller earthquakes formed as the displaced plate boundary tries to adjust itself.
Many scientists hope to use foreshocks to predict upcoming earthquakes. In particular, the East Pacific Rise transform faults show foreshock activity before the main seismic event. Reviews of data of past events and their foreshocks showed that they've a low number of aftershocks and high foreshock rates compared to continental strike-slip faults. (McGuire et al., 2005)
Aftershocks (and foreshocks) occur with a pattern that follows Omori's law. Omori's law, or more correctly the modified Omori's law, is an empirical relation for the temporal decay of aftershock rates. In 1894, Omori published his work on the aftershocks of earthquakes, in which he stated that aftershock frequency decreases by roughly the reciprocal of time after the main shock.

n(t) = frac

where

p modifies the decay rate and typically falls in the range 0.7–1.5. According to these equations, the rate of aftershocks decreases quickly with time. The rate of aftershocks is proportional to the inverse of time since the mainshock. Thus whatever the odds of an aftershock are on the first day, the second day will have 1/2 the odds of the first day and the tenth day will have approximately 1/10th the odds of the first day (when p is equal to 1). These patterns describe only the mass behavior of aftershocks; the actual times, numbers and locations of the aftershocks are 'random', while tending to follow these patterns. As this is an empirical law values of the parameters are obtained by fitting to data after the mainshock occurred and they've no physical basis/meaning.
The other main law describing aftershocks is known as Bath's Law and this says that any mainshock typical has an aftershock approximately 1 magnitude (on average 1.2) less than its mainshock. Aftershock sequences also typical follow Gutenberg-Richter scaling.
Aftershocks are dangerous because they're usually unpredictable, can be of a large magnitude, and can collapse buildings that are damaged from the mainshock. Bigger earthquakes have more and larger aftershocks and the sequences can last for years or even longer especially when a large event occurs in a seismically quiet area; see, for example, the New Madrid Seismic Zone, where events still follow Omori's law from the mainshocks of 1811-1812. An aftershock sequence is deemed to have ended when the rate of seismicity drops back to a background level; for example, no further decay in the number of events with time can be detected.

Further Information

Get more info on 'Aftershock'.

External Link Exchanges

Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:

<a href="http://aftershock.totallyexplained.com">Aftershock Totally Explained</a>

Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned.