PSN-L Email List Message

Subject: Re: Earthquake prediction messages
From: JD Cooley jdcooley@.............
Date: Sun, 17 Sep 2000 20:31:54 -0700

I agree with Larry and others that earthquake predictions do not belong on 
this mailing list.  There are a number of web sites that are dedicated to 
earthquake predictions and that is where the predictions belong.

I used to post to one of those bulletin boards and became the "keeper of 
hits and misses".  Up to that time, no one was actually keeping track of 
how accurate the predictions were (expect for the predictions by the 
"famous person" that had the web site).

Of course I had to set up some guidelines for determining hits and 
misses.  A specific location (within a radius of a stated number of miles), 
a specific time (no limit), and a specific magnitude.  Then I gave a a 
"fudge factor" of 10%.  It was mentioned by the "famous person" that he had 
been working on a method of grading predictions and it included all of the 
above, but also a "quality factor".  In other words, what are the odds of 
that quake happening?  After all, if I were to predict a M3.5 within 50 
miles of San Francisco during the month of September, 2000, I would be very 
confident that I would get a hit!  Over time, I'm sure I would be very 
nearly 100% accurate.

When I started "grading" hits using the odds factor, it really showed a lot 
more than just a hit or miss.  I was asked to stop using the grading system 
because some people would get so discouraged that they would stop posting 
earthquake predictions.  I stopped using the grading system, but still feel 
it is necessary.

There are some problems with earthquake predictions that many people don't 
think about.  First of all, when someone predicts an earthquake and they 
get a "hit", what about the other earthquakes (with magnitudes that could 
cause damage) that they *didn't* predict?  But, I think the major thing 
that needs to be considered about earthquake prediction is what, if 
anything, should be done in an area where a large earthquake has been 

Let's say that a person/method can predict 90% of all quakes in a 
particular area.  Let's further say that the magnitude accuracy is within 
+/- 10% of the actual magnitude.  Since most predictions are not for a 
specific date and time of day, let's say that the accuracy for time is 
within +/- 3 days.

I think we would all agree that that method was very, very good.  Now, this 
ficticious method predicts a M7.1 earthquake within 25 miles of San 
Francisco on September 27, 2000.  Of course, how far ahead of the predicted 
quake the prediction is made is important, but let's say it was made today, 
September 17, 2000.  So, we have 10 days!  What does the government do 
about this?  Do we evacuate all of the people from a 25-mile radius from 
San Francisco from September 23 though October 1?  I think you can see 
where I'm going with this.

I would like to say that there are some people/methods of predicting 
earthquakes that have *some* merit.  Although I had not visted the web site 
I mentioned above, I did go to it after the "Hector Mine" earthquake in the 
Twentynine Palms area just to see if anyone had predicted that one.  I 
found that for a few days before (perhaps as much as a week before) two 
people in particular were warning of a large quake in the Twentynine Palms 
area.  In fact, one of them went as far as to say "If I lived in Twentynine 
Palms, I' get out of town for the weekend."  Interesting!!

"JD" Cooley
Poway (San Diego County)


Public Seismic Network Mailing List (PSN-L)

[ Top ] [ Back ] [ Home Page ]

Larry Cochrane <cochrane@..............>