Newsgroup sci.geo.earthquakes 6074

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Ron Hill wrote:
> 
> Can someone explain - is the Richter scale logarithmic or..?
> How is it based?
Try this link:
  http://wwwneic.cr.usgs.gov/neis/general/handouts/measure.html
-- 
Judson McClendon
Sun Valley Systems    judsonmc@ix.netcom.com

Ron Hill wrote:
> 
> Can someone explain - is the Richter scale logarithmic or..?
> How is it based?
Click on this:
 http://wwwneic.cr.usgs.gov/neis/general/handouts/richter.html
-- 
Judson McClendon
Sun Valley Systems    judsonmc@ix.netcom.com

pv wrote:
> 
> In article <3283A847.4CF9@sequent.com>, Bill Lee  wrote:
> 
> > Folks,
> >         is Portland Oregon and its surronding suburb on earthquake
> >         ground ? When was the last earthquake in this area and
> >         what magnitude was it ?
> >         What is the house insurance for earthquake in this area ?
> > wle
> 
> yes, Portland is on earthquake ground. It ranks among the top cities in
> America for earthquake hazard and on top of this is extremely vulnerable
> to volcanic disruptions. I suggest you do some searching on the net for
> earthquake data, coastal Oregon sits very close to the Cascadia subduction
> zone,  an area of great earthquake potential. I don't live in the area so
> I don't know about insurance.
> 
> --
> paulus@sirius.com
> www.sirius.com/~paulus
> 
> ---------------------------here in S.F. CA--------------------
Yes,  I'd say its active, Grew up in Portland and recall some in the
early 50's or late 40's.  Portland is also about the only city in this
country, outside of Hawaii that has a Volcanoe inside the city limits..
Dale Peterson

A serious question from me for once. :)  In my little blurbs here and on
comp.risk, I was making fun of an earthquake insurance agency that sits
on the fault it insures.  In fact, I think it should locate in Chicago!
However, several people have written back that it would be perfectly
fine in Sacramento.  In fact, many agencies are locating there because
it is "fault free" according to the maps.  Now, I look at the maps and
see that S. is being heavily sheared by San Andreas motion and might not
be that 'safe'.  Does anybody have the strain rate of this area, or a
recent seismic hazard evaluation?  It seems silly to concentrate every
relief computer in the state there.
Harold Asmis (at home)

I can't give you the exact numbers, but if memory serves the area of
greatest magnitude is, in Portland, the West Hills area (4-4.5?). I've
heard reports of studies confirming 8.0+ quakes at the plate boundary
offshore. I know that there's a sesmic stability map available; you
may be able to get one by contacting the City of Portland's civil
engineering group.
Bill Lee  wrote:
>Folks,
>	is Portland Oregon and its surronding suburb on earthquake
>	ground ? When was the last earthquake in this area and
>	what magnitude was it ? 
>	What is the house insurance for earthquake in this area ?
>wle

Harold and Lise wrote:
> 
> A serious question from me for once. :)  In my little blurbs here and on
> comp.risk, I was making fun of an earthquake insurance agency that sits
> on the fault it insures.  In fact, I think it should locate in Chicago!
> 
> However, several people have written back that it would be perfectly
> fine in Sacramento.  In fact, many agencies are locating there because
> it is "fault free" according to the maps.  Now, I look at the maps and
> see that S. is being heavily sheared by San Andreas motion and might not
> be that 'safe'.  Does anybody have the strain rate of this area, or a
> recent seismic hazard evaluation?  It seems silly to concentrate every
> relief computer in the state there.
> 
> Harold Asmis (at home)
Hello Harold!
Where would you find a CA location that was _relatively_ safer?
History suggests that Sacramento suffers far less damage in the
large events.  Before they had dams, flooding was a big problem.
Under the worst possible combination of events, such as a quake
broken dam with a full lake behind it, there could be significant 
losses.  The earth is full of surprises.  Study the flood maps too.
Richard Adams

Harold and Lise wrote:
> 
> A serious question from me for once. :)  In my little blurbs here and on
> comp.risk, I was making fun of an earthquake insurance agency that sits
> on the fault it insures.  In fact, I think it should locate in Chicago!
> 
> However, several people have written back that it would be perfectly
> fine in Sacramento.  In fact, many agencies are locating there because
> it is "fault free" according to the maps.  Now, I look at the maps and
> see that S. is being heavily sheared by San Andreas motion and might not
> be that 'safe'.  Does anybody have the strain rate of this area, or a
> recent seismic hazard evaluation?  It seems silly to concentrate every
> relief computer in the state there.
> 
> Harold Asmis (at home)
Hello Harold!
Where would you find a CA location that was _relatively_ safer?
History suggests that Sacramento suffers far less damage in the
large events.  Before they had dams, flooding was a big problem.
Under the worst possible combination of events, such as a quake
broken dam with a full lake behind it, there could be significant 
losses.  The earth is full of surprises.  Study the flood maps too.
Richard Adams

Tel me anybody what a difference makes among Mb, Ms, Ml on magnitude?
Thank You
Francesco