Hi Brett- I have been following Your & Dave's development of your Super =
Home Brew Z and am always impressed when you make a comparison with the =
very nice commercial =

Nanometrics Trillium Compact 120 sensor.

Did you start with Sean-Thomas Morrissey's:  STM-8 Leaf Spring Seismomet=
er design?
see http://www.eas.slu.edu/People/STMorrissey/index.html

Can you come up with a cost estimate of your Supre Home Brew (SHB), and =
cost for the 120?   =

Do you plan on selling your SHB?

Congratulations for developing such a magnificant Seis.....Jim =


Jim O'Donnell BC-Geophysics =

Geophysical Consultant/Contractor
Geotechnical/Geothermal/Oil & Gas/Mining Applications
Seismic Surveys- Surface Waves, Refraction, & Reflection
Ground Penetrating Radar, Resistivity, Magnetic, & VLF-EM Surveys
Geophysics@..........  702.293.5664  702.281.9081 cell   =

Boulder City, NV


---------- Original Message ----------
From: Brett Nordgren 
To: psnlist@..............
Subject: Re: Period of seismic units
Date: Sat, 16 Oct 2010 10:35:35 -0400

Good question.

It is mostly about how many quakes you are likely to see.  Even =

though there are many quakes every day in California, not many are =

large enough or close enough to see above the seismic background =

noise, which is much higher at the higher frequencies.  You might =

only see one quake every few days.  And to some degree the nearer =

quakes aren't as 'interesting', rarely showing much in the way of =

distinct phases--just a single, fairly short, pop.

With a good longer-period instrument and a good location, you may see =

several distant quakes per day lasting for many minutes and sometimes =

showing multiple phases.  Some of these will be the ones you hear =

about in the news.

The best of all worlds is a broadband instrument covering both high =

and low frequencies, which can be tuned to see either type of quake =

simply by changing the WinSDR filter and gain settings.

see:   http://bnordgren.org/seismo/gif_images.htm

I suspect the reason that most on-line helicorder traces are filtered =

to long periods (excessively filtered in my opinion) is to avoid =

confusing the earthquake traces with local noise, for folks who =

aren't familiar with what they are seeing.  The people who are really =

studying the local quakes get the raw data files and would seldom, if =

ever, look at the filtered on-line traces.

Brett

At 10:32 AM 10/15/2010, you wrote:

>>It is about this geophone vs lehman or other long period instruments. =
In
>>California you have many local quakes. These quakes have frequencies
>>higher than long distance quakes. What is the logic of (just/or =

>>popularity of) long
>>period instruments out there? What precipitated this trend? The 1-5 =

>>Hz units should be better on local events -- which you have a lot.
>There are many California quakes and there is the activity in =

>Washington State and Yellowstone but you never see local seismic =

>detectors being posted with periods of 1-4.5 Hz -- except possibly =

>tchannel.  Shouldn't these units help differentiate human noises =

>like quarry activity from smaller local earthquake activity?
>




__________________________________________________________

Public Seismic Network Mailing List (PSNLIST)

To leave this list email PSNLIST-REQUEST@.............. with =

the body of the message (first line only): unsubscribe
See http://www.seismicnet.com/maillist.html for more information.
Hi Brett- I have been following Your & Dave's development of y=
our Super Home Brew Z and am always impressed when you make a comparison=
 with the very nice commercial 
Nanometrics Trillium Compact 120 sens=
or.

Did you start with Sean-Thomas Morrissey's:  STM-8 Leaf Spring Seismometer design?
see http://www.eas.slu.edu/P=
eople/STMorrissey/index.html

Can you come up with a cost esti=
mate of your Supre Home Brew (SHB), and cost for the 120?   Do you plan on selling your SHB?

Congratulations fo=
r developing such a magnificant Seis.....Jim 

=
Jim O'Donnell BC-Geophysics 
Geophysical Consultant/Contractor
Geo=
technical/Geothermal/Oil & Gas/Mining Applications
Seismic Survey=
s- Surface Waves, Refraction, & Reflection
Ground Penetrating Rad=
ar, Resistivity, Magnetic, & VLF-EM Surveys
Geophysics@...........
  702.293.5664  702.281.9081 cell   
Boulder City=
, NV


---------- Original Message ----------
From: Brett No=
rdgren <brett3nt@.............>
To: psnlist@..............
S=
ubject: Re: Period of seismic units
Date: Sat, 16 Oct 2010 10:35:35 -=
0400

Good question.

It is mostly about how many quakes you=
 are likely to see.  Even 
though there are many quakes every da=
y in California, not many are 
large enough or close enough to see ab=
ove the seismic background 
noise, which is much higher at the higher=
 frequencies.  You might 
only see one quake every few days. &nb=
sp;And to some degree the nearer 
quakes aren't as 'interesting', rar=
ely showing much in the way of 
distinct phases--just a single, fairl=
y short, pop.

With a good longer-period instrument and a good loc=
ation, you may see 
several distant quakes per day lasting for many m=
inutes and sometimes 
showing multiple phases.  Some of these wi=
ll be the ones you hear 
about in the news.

The best of all wo=
rlds is a broadband instrument covering both high 
and low frequencie=
s, which can be tuned to see either type of quake 
simply by changing=
 the WinSDR filter and gain settings.

see:   http://bno=
rdgren.org/seismo/gif_images.htm

I suspect the reason that most o=
n-line helicorder traces are filtered 
to long periods (excessively f=
iltered in my opinion) is to avoid 
confusing the earthquake traces w=
ith local noise, for folks who 
aren't familiar with what they are se=
eing.  The people who are really 
studying the local quakes get =
the raw data files and would seldom, if 
ever, look at the filtered o=
n-line traces.

Brett

At 10:32 AM 10/15/2010, you wrote:
>>It is about this geophone vs lehman or other long period in=
struments. In
>>California you have many local quakes. These qu=
akes have frequencies
>>higher than long distance quakes. What =
is the logic of (just/or 
>>popularity of) long
>>peri=
od instruments out there? What precipitated this trend? The 1-5 
>=
>Hz units should be better on local events -- which you have a lot.>There are many California quakes and there is the activity in 
=
>Washington State and Yellowstone but you never see local seismic >detectors being posted with periods of 1-4.5 Hz -- except possibly =

>tchannel.  Shouldn't these units help differentiate human n=
oises 
>like quarry activity from smaller local earthquake activit=
y?
>




__________________________________________=
________________

Public Seismic Network Mailing List (PSNLIST)
To leave this list email PSNLIST-REQUEST@.............. with 
th=
e body of the message (first line only): unsubscribe
See http://www.s=
eismicnet.com/maillist.html for more information.