Frequency of earthquakes
Doug Andersen
"favorite" Christian fundamentalists and he brought up the subject of
the "end of the world". He claimed that one of the primary signs
was increased earthquakes and that indeed the number of strong earthquakes
had been increasing exponentially over the past 100 years. He claimed
to have gotten his data out of a Hal Lindsay book, and Lindsay supposedly
called "some earthquake center in Colorado" to get his data.
Can anyone point me in the direction of where I might find data to
confirm/refute his point. Or better yet, does anyone have any data
handy that they might like post? I appreciate any and all help.
Excuse me if I've posted to any inappropriate newsgroups.
--
Doug Andersen
ha...@Sugar.NeoSoft.com
cct...@csc.canterbury.ac.nz
I asked this question just recently and posted a summary a while back but
I didn't save a copy. However working from memory, what they are saying is
both true and false. There is absolutely no evidence for any actual increase
in the numbers of earthquakes on a global scale. The number of ``big ones''
has remained relatatively stable, with the usual statistical fluctuations,
for as long as there are earthquake records. There are two factors which
can and do create an increased number of earthquakes on a local scale. One
is building a big dam and then filling it with water when there are faults
in the area. If the volume of water is cycled, as it tends to be with
lake used for hydroelectricity generation, this tends to set off earthquakes.
But from all accounts this are tiny earthquakes, you cann't feel them, you
need a seismograph to detect them. The second thing which can cause localized
increase in earthquake frequencies is deep drilling (e.g. for oil) near fault
lines. This is because there is an out flow of material such as water or
drilling mud which tends to lubricate the fault and allow easier movement.
But again these earthqakes tend to be small.
Some of the increase in earthquakes talk is abuse of data. Since the 1960's
when nuclear testing went underground, defense people have installed a
world wide network of seismometers to monitor nuclear blasts. These also
pick up earthquakes (surprize, surprize :-). So there has been a vast
increase in the number of recorded earthquakes as a direct result of better
and more observing equipment. The defense people have been good about releasing
data to civilian scientists. Some unscrupilous people (Greenpeace included)
have used this increase in observed earthquakes to say that there is an
actual increase and then they come in pushing their own political wheelbarrow.
Just off the top of my head I think the long term average of ``big ones'' i.e.
greater than magnitude 6 is about 62 per year. Thats more than one a week.
With better communications worldwide more of these earthquakes are brought
to the attention of the general public giving the impression the earth is
shaking itself to pieces. In actual fact there have been some quiet years
recently where the number of big ones was significantly lower than the long
term average, I think 1988 was one.
Try finding a book on earthquakes by George Eiby, it has gone through several
revisions, the most recent being in the mid 1980's, it has an appendix with
lists of very big earthquakes in the back of it.
> --
> Doug Andersen
> ha...@Sugar.NeoSoft.com
--
___
Bill Rea (o o)
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