July 6, 2006

• Earthquakes, Plates and Trigger Events

  

  This comment has had me thinking about earthquakes even more than I usually do:

  …have
  you noticed, perhaps, that your subscription to the earthquake warnings
  has generated a whole lot more since the bombardment of iraq? that’s
  why i have nicknamed him ‘george w.m.d. shrub’, i sincerely believe
  that the constant detonation of explosives during the iraq war has
  unhinged many of the plate margins leading to many more earthquakes and
  volcanic activity around the world.

  Posted 7/4/2006 at 8:11 AM by the_nthian

  That’s a neat trick, because hardly a day passes that I don’t think
  about earthquakes anyway.  I am apparently more sensitive than
  most people are to little shakes occurring locally and big ones at a
  distance.  That fact became a topic of discussion locally about
  fifteen years ago when we had a swarm of little earthquakes here.

  For days and daze I had been asking Greyfox, “Did you feel that?” 
  His answer was always, “no,” and very soon he began giving me funny
  looks when I’d ask.  Soon after that, he expressed the opinion
  that I was imagining things.  Then, when I felt one while we were
  visiting our friends Bear and CeeCee, I asked that question
  again.  Bear looked blankly confused, Greyfox looked slightly
  worried and more than slightly scornful, and CeeCee looked surprised
  and relieved as she chirped, “You felt it, too!?”

  CeeCee and I decided to ask around and find out how many other people
  were aware of the little shakes.  I found no others, and she found
  only one:  a nurse at the local health clinic, also female. 
  Until recently, I’d had no easy way to independently confirm what our
  senses were indicating.  Then, the USGS changed their reporting
  system and began allowing users to change the settings in the new Earthquake Notification Service  (formerly the BIGQUAKE service).

  I reset the local region sensitivity for a few days until I got tired
  of the mass of email it generated.  One thing I learned was that I
  feel some local quakes below magnitude 2, and can be awakened from a
  sound sleep by some below magnitude 4.  But I digress.

  My intention had been to respond to Ian’s question.  After much
  thought, I failed to come to any definite conclusion.  I asked
  Greyfox if he thought bombardment in Iraq would cause increased seismic
  activity.  He was fairly certain that it wouldn’t, or that it was
  at least highly unlikely.  I’m not sure.  I have no idea how
  likely or unlikely it is.  I am fairly certain it is possible.  I suspect that the the recent increase in activity might more likely be attributable to global warming and retreating glaciers, but I’m not sure.

  Both factors could be contributing.  It’s also possible that
  some quakes are being triggered by the removal of oil from
  belowground.  Small changes can, over time and space, trigger big
  effects.  That’s 
  The Butterfly Effect. 

  

  “The butterfly effect is the idea that in a
  chaotic system, a
  very small change to the system applied at a certain point
  in time makes the future change in a very dramatic way. 
  Something as small as a butterfly flapping its wings now 
  might affect the weather system on a global scale six
  months in the future.”

  I felt that the likelihood of explosions
  on the surface causing shifts belowground was increased by the
  fact of its being in that location in the boundary zone where more
  separate plates interact than at any other point on the planet. 
  Greyfox thought that the fact that the crust is greatly broken up,
  crumbled, in that area would lessen the likelihood of small impulses
  causing large effects.  His opinion is strongly held, while mine
  rests entirely on uncertainty.  That certainty/uncertainty factor
  has absolutely no bearing on the theory’s truth or fallacy.  Of
  that I am certain.

  

  The African, Arabian and Indian plates come together in that region.  Well… that’s not precisely correct.  They meet there, share common boundaries, but are actually spreading, pulling apart.  That process has formed the Y-shaped triple rift
  of the Red Sea, Gulf of Aden, and Great Rift Valley.  The link
  just above goes to a page detailing how that spreading will eventually
  separate a new Somali Plate from the African.

  When I visualize the action of plate tectonics or continental drift, I
  see a process similar to what I have seen on the surface of a pot of
  fudge cooking or in a retort of molten metal.  The crust on the
  surface breaks up and the chunks shift around, driven by the convection
  currents within the liquid beneath.

  More links:

  bigger “better” (more detailed) plate_map
  an even better one showing directions of drift
  Sciencedaily article on using fractals to predict quakes
  map of quake epicenters 1980-1990
  Do old glaciers cause new earthquakes in New Madrid, Missouri?
  earthquake triggering processes

  PS:  I felt this one
  at magnitude 1.4 early this morning.  It woke
  me.  I didn’t report to the USGS that I felt it.  I guess
  it’s a matter of intellectual vanity or something of that sort.  I
  know that if I report every little shake I feel, I’ll get a reputation
  as a crank.  My prime criteria for whether I report a quake or not
  is whether I hear it (rumbles in the earth and/or pops and creaks in
  the building) or it sets my hanging plants swinging and rattles my
  earthquake indicator (hanging keys).

  • 2:43 pm
  • 9 Comments