MadSci Network: Earth Sciences

Re: Why do earthquakes strike certain areas over and over again???

Date: Tue Apr 3 15:52:14 2001
Posted By: Sarah Fretz, Undergraduate, Biology, New Mexico Tech
Area of science: Earth Sciences
ID: 984516022.Es


You were wondering why some places get "hit" by earthquakes time and time 
again.  And some places don't seem to feel a quake at all.  Sorry I've 
taken so long in replying, I'll do what I can.  

Are you familiar with "plate tectonics?"  The cut-and-dry explanation of 
earthquakes is that most of the land and ocean bottoms "float' around on 
the more fluid parts of the earth and crash into each other in many ways.  
Sometimes, as the plates pull apart or stretch out, an earthquake can also 
happen.  I like this site- it's got little movies you can click on to 
learn more about tectonics and how plates move.

This is a link to a map of South America and its most recent significant 
earthquakes. http://wwwnei 

Notice how there are some earthquakes that happen nowhere near the plate 
boundaries (yellow lines).  Small quakes can and do happen all over the 
place because the earth is still shifting and changing.  Small quakes can 
be caused by something so small as an underground limestone cave 
collapsing to a something so grand as a new fault forming.

Because the Earth is spinning in space, the fluid insides move around 
too.  In some places, the crust or plates are a little thin, and molten 
rock comes out as a volcano.  Volcanoes and earthquakes often go hand-in-

Another place to look is right next door, in the MadSci library (under 
Earth Sciences), there's a link to this page:
the title in the library is "plate tectonics and seismic waves"

All of these sites combined can tell you much more than I can in only a 
few words.  Good luck, and happy hunting!

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