El Diario – 18 Octubre 2014

This week when we got to work we were asked if we felt the tremor (check out the Earthquakes tab) earlier in the morning (we didn’t).    That got me to wondering what Chileans believe is the difference between an earthquake and a tremor.  They called this year’s 8.2 in Iquique and the 7.1 off the coast of Easter Island an earthquake and Tuesday’s 5.2 a tremor.

To further complicate matters – on the same day last August we had a 6.5 tremor while Napa had a 6.0 earthquake.  Confused yet?  Well this got Wooly thinking (oh, oh) about what the difference is between a tremor and an earthquake.  After checking numerous sites on the web that all disagreed about the intensity required to promote a tremor to earthquake status Wooly came up with one conclusion.

Armed with that conclusion Wooly decided to test it at work the next morning.  When he asked his gringo friends they pretty much concluded anything above 6.0 would qualify as a full-fledged earthquake.  A couple of them said before they came to Chile that number would have been around 5.0 or so.  Yet when the Chileans were asked they all pretty much agreed it takes a 7.0 or greater to be called a bona-fide earthquake.

So there you have it.  If you live in an area where ground movement is rare or occasional, anything you feel is an earthquake.  Yet someone living in an area with frequent ground movement it takes a higher number.  Or in the case of Chile with lots of large earth movements (http://en.wikipedia.org/wiki/List_of_earthquakes_in_Chile) it seems a 7.0 or greater is required before the local folks grant a tremor earthquake status.  For those who remember, just think of the damage the 1989 6.9 Loma Prieta (the World Series earthquake) caused and how many lives were lost or the 1994 6.7 Northridge quake in the L.A. area.   I had to chuckle last March when a friend commented on the 5.1 earthquake they had in L.A. had him shook up.  Sorry, had to do that.

And what about the Valparaiso and Viña del Mar areas where we live?  Here is a list of Valparaiso earthquakes:

  • 1730 – 8.7
  • 1737 – 7.7
  • 1822 – 8.5
  • 1829 – 7.0
  • 1831 – 7.8
  • 1833 – 7.7
  • 1900’s – Nothing
  • 2000’s – Nothing

A 200 year gap without any significant earthquakes makes us overdue for a very large one.  It could possibly even be in the 9.x range.  Here’s hoping it doesn’t happen while we’re here, or if it does nothing falls on us or collapses underneath us.

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