PSN-L Email List Message

Subject: Re: Period
From: tchannel1@............
Date: Tue, 3 Jul 2007 08:13:23 -0600

 Hi Geoff,

>Do you know if anyone has ever used a laser pointer
in a seismic sensor ? Possibly using surfaced mirrors
to provide mechanical amplification like a lever arm ?

No I do not.  Thanks for all this good information.  Ted

----- Original Message ----- 
From: "Geoffrey" 
Sent: Tuesday, July 03, 2007 4:44 AM
Subject: Re: Period

> Hello tchannel1;
> This is a response to your post and intended
> for everyone at PSN.
> A period range of 0.2 Hz to 2Hz is by far the best
> range for seeing P and S of most EQ signals
> If one lives in a noisy area with lots of vehicular
> traffic this is the best range to use. In this range you
> should be able to crank up the gain until you see
> both low and high frq noise about +/- two samples
> maybe four then you should be able to see a 4.0
> regional quake at 6 degrees of distance as the
> guideline for a MDL (Minimum discernable level).
> The smaller the bandwidth the less the noise.
> If you are in a quiet area by all means open up the bandwidth
> to see the close quakes better.
> If you have like a 24 bit A/D converter you can make the gain
> adjustable simply be looking at 8 or 12 or 16 bits and scaling
> everything else then you can digitally set the gain from
> the keyboard.
> If you program a modulo recorder of 12 minutes or so
> there are almost no earthquakes of any size
> that you will miss with a computer oriented recorder
> and a seismic alarm that works something like a venus fly trap
> trigger hairs.
> Do you know if anyone has ever used a laser pointer
> in a seismic sensor ? Possibly using surfaced mirrors
> to provide mechanical amplification like a lever arm ?
> If you do not build your own electronics and program your own
> software then most probably forget these finer details.
> Like Always, I am no expert but i do have several broken
> years of practical experience.
> To me an Amateur can be a layman who simply watches the signals
> and cares nothing more about the science since an amateur receives
> No pay for his hobby. Laymen Professional Expert are different ideas.
> I think you can find all three in any amateur group. I am an Amateur 
> layman
> with some formal technical education and experience but no 
> degree\certificates
> that means anything.
> The range I tell you here is from personal experience over the past 13 
> years.
> I have found the 500LB geophone used all over the world by the USGS gives 
> the
> best signal right down to 20 seconds even tho it is a 1sec free period 
> device.
> It does not have the severe natural damping of the smaller geophones
> but does have a very powerful magnet.
> My thought is this;
> The sensor should be in a vacuum and have a very powerful magnet
> and in a faraday shield otherwise the sensor will typically be marginal at 
> best.
> Everything needs to be shielded and bonded between the Computer including 
> the sensor.
> AntiAlising filtration by whatever means prior to conversion/recording by 
> the A/D converter.
> Do not use the sensor coil for damping because that reduces sensitivity 
> but instead
> use a seperate magnet/Copper Plate arrangement. The preamplifier to be a
> differential type with both +/- of the opamp equalized for DC.
> Put as little load on the sensor as possible.
> It used to be easy to get copper in Arizona but not any more
> unless you pay lots of cash, copper has become outrageously expensive
> along with everything else.
> It seems to me they (My Country/USA) do not want people playing
> around with Science and Technology unless they are rich or
> Formally educated. I think they (My USA) are overly Religious and overly 
> paranoid.
> The majority of people here are not well enough educated (including 
> myself).
> It is humbling to note that after study of life that 
> intelligence/education are not necessary for survival.
> Winquake is the best public seismic program I have seen for the layman.
> I will convert my data to text to use in winquake and find the data
> easier to analyze. But to be most precise and accurate I will read
> using my own program on a sample by sample bases.
> Winquake gives a sort of standard for PSN and lets people
> share their data. But I have found that if you are converting
> your own data into PSN form you must start the first sample
> relating to an exact start of minute or the times will not be right.
> In Winquake You must test your sample rate and make sure its right.
> Start all your data for winquake at HH:MM:00.0 the seconds always
> being zero for your very first sample. You need cal markes from
> WWV/CHU or something like that to see the top of second zero
> in each minute.
> Say Minute 59-60 second mark goes high at sample #1025
> use sample #1024 as the very first sample and stop the samples
> at the N= The next cal mark high - one sample at the end. Winquake
> should agree that the times are all right so long as you got the
> sample rate right.
> Winquake does not give me good times if I do not follow this idea.
> I can not just start out in the middle of a minute and end just anywhere.
> Without Cal marks of some standard type the times for the layman are 
> uncertain.
> Winquake needs a FFT waterfall display to see a movie like of
> shifting frequencies over time.
> Possibly in 1024 sample chunks advancing one sample for the next 1024.
> Nothing fancy, Black and white and shades of gray,  totally suitable.
> Regards;
> geoff
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