[rollei_list] Re: Off-Topic: the Earthquake and Me
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Thu, 25 Aug 2011 21:31:31 -0700
----- Original Message -----
From: "Jim Brick" <jim@xxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Thursday, August 25, 2011 4:33 PM
Subject: [rollei_list] Re: Off-Topic: the Earthquake and Me
I guess this is the difference between SoCA and NoCA. Here
in Silly Cone Valley, we sit on the Hayward Fault and the
San Andreas Fault (both major major faults that will
eventually wreak total havoc), but there are myriad other
smaller faults all over the place here which rattle
constantly. Parkfield, just south of here is the earthquake
center of the US/world. A USGS person said that Parkfield is
nearly in constant motion (obviously a slight exaggeration),
but that's where he USGS does a major part of their
research.
http://earthquake.usgs.gov/research/parkfield/index.php
Here is a CA map, notice the number of between 3/4/5
earthquakes over the past week, many right here in the Bay
Area & Salinas Valley.
http://earthquake.usgs.gov/earthquakes/recenteqscanv/
So I wasn't kidding - if it doesn't throw you to the ground
or floor, it's termed a 'foot massage'. Maybe a slight
exaggeration... ;-)
:-)
Jim
There are constant very small quakes here too. Same
thing, lots of small faults. The USGS publishes a chart with
relatively small quakes on it so one can see what's going
on. The mailing list I'm on lists only quakes above a
certain size, I think its 4.5 for US quakes and larger for
those in other parts of the world. Anyone who thinks terra
firma is really firma is fooling themselves.
The problem with the large fault lines is that no one
is sure of how much stress needs to build up before they
move or what the real statistics are since quakes can be
very far apart in time and records do not go back very far
by geological standards. Some quake records are in the form
of fossilized trees and in magnetic evidence in rock
formations. Those can give a hint of enormous quakes in the
very distant past. The strength of materials of the earth's
crust limits the amount of stress that can build up before
something gives way but even so a quake of nearly 10 can
occur and they have. While Los Angeles is not on the San
Andreas fault we are not too distant and another quake like
the 1906 one would be very strong here. There was an even
stronger quake around 1850, I think, can't remember the
exact date and don't want to look it up now. No big quake
since 1906. If the statistics are right there should be one
about every fifty years. However, the statistics, as I
indicated above may be all screwed up because we don't
really have a long enough record. So, here we are with out
civiilized society living in the midst of earthquakes,
floods, brush and forrest fires, landslides, serious storms
and the sea conditions they produce, extreme heat, even
tornadoes, which, while rare, do occur here. The Franciscan
Fathers have a lot to answer for.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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