Question of the Week

Have earthquakes been more frequent recently?

Sun, 12th Jun 2011

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Question

Kacey asked:

I have a question about earthquakes. It seems like there have been an awful lot of big earthquakes lately. Is there some reason that they seem to be a lot recently? Like once one of the plates moves it somehow affects a lot of the other plates too. Or is it just a coincidence? I live very near the Hayward fault in the San Francisco bay area, so should I really start earthquake proofing my house and lab now?

Answer

We posed this question to Gopal Madabhushi from the University of Cambridge...

Gopal -   Hello.  This is (Gopal Marbushi).  I'm a reader in geotechnical engineering at the University of Cambridge.  It is true that large earthquakes have happened in close succession recently.  For example, two larger plates in (c) Photo Marco Dormino/ The United Nations" alt="Port au Prince" />Christchurch in New Zealand and a very large earthquake in Japan.  However, the fault systems in Japan and New Zealand are quite separate and there are no interconnections between them so, the earthquakes occurring together is a pure coincidence.  Having said that, the two earthquakes near Christchurch may be interconnected, with stress release from one fault affecting the other.  If you live in a seismic area, it is always better to consider earthquake proofing your house.

Diana -   Earthquakes haven’t occurred anymore in the last 20 years than they have done over the last century, but we have far more seismograph stations and much better methods of reporting communication and accessible news.  So, we’re being deluged with more stories about earthquakes which we know a lot more about.  Plus, there are many more people in the world now who can be affected by such earthquakes. 

 

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I don't believe the absolute number of earthquakes, magnitudes, and etc have changed much over time.  There certainly may be a reporting bias that we now hear of earthquakes in Malaysia, Haiti, Chile, and elsewhere that might not have made the news 50 years ago.

Yet, even so, many minor earthquakes hardly even make the local news.

I have wondered about multiple earthquakes along the same fault-line and tectonic plate.  I don't believe that there is a high correlation between major San Francisco and major Los Angeles earthquakes, although there apparently was a cluster of major earthquakes in California in 1992 spanning a few months.

http://en.wikipedia.org/wiki/List_of_earthquakes_in_California

Foreshocks and Afershocks seems to be complicated.  In some cases, foreshocks are believed to have occurred over a year before the main earthquake.

Be careful of reporting biases.  Note the Wikipedia page above lists several 4-5 magnitude earthquakes post 2000, but very few pre 2000.

CliffordK, Sun, 5th Jun 2011

My guess is that whales are able to set off earthquakes by focusing their subsonic songs on the faults and structures which can move during a quake. The increased prevalence of earthquakes is coincidental to the decline in the whale population due to whaling and overfishing. grizelda, Sun, 5th Jun 2011

Have earthquakes been more frequent recently?  If we are discussing recent history then one must say: "Yes, they most certainly have been".

However, without input from our friends like the Ammonites one truly may never know for sure.   Incognito, Wed, 8th Jun 2011

2012, people.  2012. jimkingwood, Thu, 9th Jun 2011

In the advent of modern technology, minor earthquakes can now be recorded.  This is not possible during ancient times, so the difference lies with the technology that is used to monitor these seismic waves. widereader, Wed, 21st Dec 2011

ONE WORD - JAPAN

And they say because of that earthquake japan is expected to get another huge one! Guess where i'm not goin anytime soon? tangoblue, Wed, 11th Jan 2012

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