XPost: sci.geo.geology, van.general, sci.geo.earthquakes   
   From: Paul@Houston.com   
      
   Skywise wrote:   
   > Paul in Houston TX  wrote in news:jgl21v$g3h$1@dont-   
   > email.me:   
   >   
   >> David Dalton wrote:   
   >>> In article ,   
   >>>  Paul in Houston TX  wrote:   
   >>>   
   >>>> David Dalton wrote:   
   >>>>> Could the recent magnitude 5.7 earthquake off the BC coast   
   >>>>> be a foreshock to a larger earthquake?   
   >>>> No.   
   >>> Why not?   Is it not located on a major fault or   
   >>> plate boundary?   
   >>>   
   >> I suppose it is possible.   
   >> However, a 5.7 is a pretty good stress reliever.   
   >   
   > Compared to what?   
   >   
   > Each point in magnitude is ~32x increase in energy, therefore   
   > it would take 32 magnitude 5.7 quakes to equal the same energy   
   > as a 6.7 quake. If you want to relieve the stress of a 7.7   
   > quake, you'd need 1000 of these 5.7 quakes.   
   >   
   > Cascadia has the potential of a magnitude 9. Let's make it   
   > easy and say we need to relieve the 'stress' of a mag 8.7.   
   > How many of these 5.7's do we need? Yep, about 32 thousand!!!   
   >   
   > The point here is that this 5.7 didn't do diddly squat to reduce   
   > the chances of a larger quake in the future.   
   >   
   > Brian   
      
   Quakes happen due to compressive stress along a fault plane   
   being relieved suddenly.   
   If the stress gets relieved in small movements before it gets   
   to the 6.7 state, the 6.7 will never happen.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)