Various of the latest list-serve comments are concerned with SNR of instruments,
so I've decided to describe a few of the things I've learned after about two
decades of intense research on the non-ideal properties of mechanical oscillators.
To the extent that linear approximations are meaningful (not really true at
low frequencies and small
amplitudes), the theoretical description of a seismometer's performance is
straightforward, and treated
in the paper I wrote, titled "Seismometer performance based on a simple theory of
instrument-generated
noise equivalent power", online at
http://physics.mercer.edu/hpage/inep/inep.html
If you look at this paper, pay close attention to the difference between
conventional instruments that output the time derivative of mass position
(velocity) and the VolksMeter (position). Because every seismometer (as Einstein
well understood, because of inertia) responds only to acceleration (tilt being a
special case), the conventional instruments measure the 'jerk' of the earth,
whereas the VolksMeter measures its acceleration. The two systems offer
synergetic
possibilities--jerk sensors better for the high frequency range and acceleration
sensors better for the low frequency
range.
Some of the recent comments are concerned wtih noise equivalent power
generated by electronic devices. Such
noise is inevitable and temperature plays a dominant role in the electronics. It
has been understood for decades
from the time of Johnson, and its treatment is straightforward. Insofar as
temperature dependence
of the mass/spring of a seismometer is concerned, this is an entirely different
issue. A common calculation of the Brownian motion of the seismic mass (which
suggests a simple advanatage to operating at lower temperatures) is
meaningless. The equation employed is based on the equipartition theorem, which
does not apply because the
number of 'degrees of freedom' in the non-ideal spring is much greater than the
number two that is assumed;
i.e., one term for the potential energy and one term for the kinetic energy (each
contribution one-half kT of thermal
energy), naively assuming a harmonic potential (based on Hooke's law which is
known to be not-obeyed).
For those interested in some of the foundation physics responsible for
seismometer difficulties due to mesoanelastic complexity, I wrote the article
"Anharmonic Oscillator" for the the 10th Ed. of McGraw Hill's
Encyclopedia of Science and Technology. Typing into Google the expression damping
anharmonicity -- will return the Access Science quote of the first part of this
article. To read the whole article you will have to either (i) pay something to
McGraw Hill or (ii) contact me and I will return a copy by email attachment.
Internal friction is intimately related to the instrument-generated noise
equivalent power and readers may find
interesting the following paper: "Harmonic oscillator potential to describe
internal dissipation", online at
http://arxiv.org/html/physics/0307016
Seismometer theory is hard enough to understand, even when based on linear
(overly idealized) approximations.
Even the professional seismologists, along with myself, have been guilty of
erroneous assumptions. I believe, after
more than a decade of trying to acquire self-consistency in at least the linear
descriptions--that I'm getting close
to a first-order approximate description that is valid for the first-cut of
instrument design. A full understanding of the real-world properties of
seismometers is truly impossible at this point in time, because we don't
understand internal friction from first principles. In the article that I wrote,
titled
"Friction at the mesoscale", Contemporary Physics vol. 45, no. 6, pp. 475-490
(2004),
I included a quote from a Nature article (Kessler) that speaks to the matter;
i.e., "It is one of the dirty little secrets of physics that while we physicists
can tell you a lot about quarks, quasars, and other exotica; there still is no
universally
accepted explanation of the basic laws of friction". As noted in the paper, I had
actually contemplated
a title "Friction, friction everywhere but in our understanding".
Randall
psn-l-digest-request@.............. wrote:
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 1 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Re: Signal To Noise Ratio
> From: "Geoff"
> Date: Tue, 6 Nov 2007 02:26:21 -0700
>
> Interesting Mr. Brad Douglas;
>
> Im not sure about any of this
> but it would be nice to understand
> what is in the front end of the
> first PIONEER SUPERTUNERS.
>
> I think there are very low noise devices out there
> but it would be useless to use them
> in any high noise environment like
> ShortWave radio.
>
> All one really needs is to keep the
> combined circuit noise below the
> ambient noise or you will have
> a hard time seeing the those signals
> riding near the natural grass.
>
> The astronomers will supercool
> their preamps to eliminate noise and
> do any broadband shifting right in
> the front end.
>
> I think i would like to have
> an Astronomical expert making the
> electronics for my geophone
> but fear I would not be able to
> afford the liquid helium to
> keep it in operation.
> :-)
>
> Regards;
> geoff
> ----- Original Message -----
> From: "Brad Douglas"
> To:
> Sent: Saturday, November 03, 2007 5:48 PM
> Subject: Re: Signal To Noise Ratio
>
> > On Sat, 2007-11-03 at 16:50 -0700, Geoff wrote:
> >> Hello Bob;
> >>
> >> Have you ever heard of a low noise
> >> GaAs op amp that is designed to work
> >> like a op177G (typical opamp) or ??
> >
> > GaAs FETs go that low in frequency and still yield gain and stability?
> > Lowest I've ever done is 144MHz and that was straining the chip,
> > yielding decreased gain (but still higher than any non-GaAs FET). If my
> > understanding is correct, GaAs is "saturated" above 2GHz, making them
> > ideal for microwave LNAs.
> >
> > Or have I entirely missed the point? :-)
> >
> >> Signal to noise ratio should be easily found
> >> in google I think it simply is like
> >> Expectided MDL signal power / Ubiquitous Noise Power
> >> The higher the ratio the better the whatever.
> >> Possibly expressed in db.
> >> For power thats 10Log(Sig/Noi).
> >
> > That's mostly accurate:
> > http://en.wikipedia.org/wiki/Signal-to-noise_ratio
> >
> >
> > --
> > 73, de Brad KB8UYR/6
> >
> > __________________________________________________________
> >
> > Public Seismic Network Mailing List (PSN-L)
> >
> > To leave this list email PSN-L-REQUEST@.............. with
> > the body of the message (first line only): unsubscribe
> > See http://www.seismicnet.com/maillist.html for more information.
> >
>
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 2 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Re: Signal To Noise Ratio
> From: "Geoff"
> Date: Tue, 6 Nov 2007 02:44:42 -0700
>
> Hello Bob;
>
> I guess I am no scientist because the basic
> idea seems so simple to me that the signal to noise
> ratio can be somewhat arbitrary in your selection
> of reference points.
>
> You pick a signal level of interest
> and make sure your S/N ratio is such
> you will actually see the signal of interest.
>
> Any signal with like 6dbv X2 above the noise
> should be visible. One that is 120db
> is a million times the noise.
>
> It all depends upon what noise you mean
> and to me that is overall "S" noise.
> White Noise. Like on an "S" meter.
>
> As any bubblehead should know ( Sub-Sailor )
> S/N is one of the sinle most important facets
> of any sensor device.
>
> I am amazed that an NMR machine can
> rattle a mole of atoms in a strong
> magnetic gradient and listen
> to them ring With various frequencies
> in response.
>
> They must have a receiver unlike anything
> I am familiar with.
>
> I would start by looking at the USGS noise levels
> then figure out what S/N ratio needs to be
> before designing a serious device.
> The place i live in here is so terribly
> noisy I need to filter right at the
> preamp to keep my electronics from
> being jammed by higher vehicular frequencies.
>
> It probably would do me little good
> to invest in high class low noise
> amplifiers at my current location.
>
> The overall noise of your system
> needs to be lower than the grass.
> To the point of diminishing returns.
> The grass being the noise in the ground
> at whatever bandwidth during a quiet
> sunday morning like 3am local time.
>
> Most people do not build their own
> devices and do not concern themselves
> with this thought.
> There are many types of noise but the only
> one of interest is the overall results.
> I cant wait until Universal Entropy Reaches Maximum
> That will be the quietist time of all.
>
> Regards
> geoff
>
> ----- Original Message -----
> From: "Bob Hancock"
> To:
> Sent: Saturday, November 03, 2007 5:06 PM
> Subject: Re: Signal To Noise Ratio
>
> Hi Geoff -
>
> Unfortunately, my knowledge of electronics is less than stellar. I am
> working at understanding concepts of seismology. As for
> electronics.....well, I'll leave that for someone else. I was hoping to
> find an answer that would allow me to apply the SNR numbers I see to the
> practical side of seismology. I understand the simple concept of an
> amplifier (boosting a signal), but unfortunately, I have no working
> knowledge of their innards or how the individual parts work by themselves
> and in concert with each other.
>
> Bob H
>
> On 11/3/07 4:50 PM, "Geoff" wrote:
>
> > Hello Bob;
> >
> > Have you ever heard of a low noise
> > GaAs op amp that is designed to work
> > like a op177G (typical opamp) or ??
> >
> > Signal to noise ratio should be easily found
> > in google I think it simply is like
> > Expectided MDL signal power / Ubiquitous Noise Power
> > The higher the ratio the better the whatever.
> > Possibly expressed in db.
> > For power thats 10Log(Sig/Noi).
> > The noise would be the reference point.
> > If you can get a 120db (coopers)
> > I think youd be in fat city.
> > The higher the overall s/n ratio
> > the smaller signals they can see.
> > Like someone sneezing next door.
> >
> > :-)
> > geoff
> >
> > ----- Original Message -----
> > From: "Bob Hancock"
> > To: "PSN"
> > Sent: Saturday, November 03, 2007 1:16 PM
> > Subject: Signal To Noise Ratio
> >
> >
> > When downloading events through IRIS Wilber II, I noticed that they listed
> > the signal to noise ratio. Most of the time the number was 1; however,
> > there were other numbers listed. I have some questions and hopefully
> > someone can answer them.
> >
> >
> > 1. What is the significance of signal to noise ratio when looking at
> > earthquakes?
> >
> > 2. How is signal to noise ratio computed?
> >
> > 3. What are the ideal numbers to look for and at what point does the data
> > become unusable?
> >
> > Thanks
> >
> > Bob Hancock
> >
> >
> >
> > __________________________________________________________
> >
> > Public Seismic Network Mailing List (PSN-L)
> >
> > To leave this list email PSN-L-REQUEST@.............. with
> > the body of the message (first line only): unsubscribe
> > See http://www.seismicnet.com/maillist.html for more information.
> >
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 3 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Unknown event
> From:
> Date: Tue, 6 Nov 2007 11:19:29 -0700
>
> This is a multi-part message in MIME format.
>
> ------=_NextPart_000_0007_01C82066.E5EE6CA0
> Content-Type: text/plain;
> charset="iso-8859-1"
> Content-Transfer-Encoding: quoted-printable
>
> Hi Folks, I got the 5.4 Guerrero, Mexico, here in Boise, at about =
> 06:42, It was followed be another one, at about 06:52 UTC. I can't =
> identify this one? =20
>
> Thanks, Ted
> ------=_NextPart_000_0007_01C82066.E5EE6CA0
> Content-Type: text/html;
> charset="iso-8859-1"
> Content-Transfer-Encoding: quoted-printable
>
>
>
> charset=3Diso-8859-1">
>
>
>
>
> Hi Folks, I got the 5.4 Guerrero, =
> Mexico,=20
> here in Boise, at about 06:42, It was followed be another one, at =
> about=20
> 06:52 UTC. I can't identify this one?
>
> Thanks, Ted
>
> ------=_NextPart_000_0007_01C82066.E5EE6CA0--
>
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 4 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Re: Unknown event
> From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?=
> Date: Tue, 06 Nov 2007 18:31:27 +0000
>
> Hi
>
> There was a ML4.3 earthquake at 06:41 in SERAM, INDONESIA (sorry for the
> caps). Maybe it was that one ?
>
> More details.
>
> http://www.emsc-csem.org/index.php?page=3Dcurrent&sub=3Ddetail&id=3D69262
>
> Regards.
> --=20
> J=F3n Fr=EDmann
> http://www.jonfr.com
> http://earthquakes.jonfr.com
> http://www.net303.net
> http://www.mobile-coverage.com/
>
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 5 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Guerrero Mexico 5.4M
> From:
> Date: Tue, 6 Nov 2007 13:48:56 -0700
>
> This is a multi-part message in MIME format.
>
> ------=_NextPart_000_0005_01C8207B.C6AAFCE0
> Content-Type: text/plain;
> charset="iso-8859-1"
> Content-Transfer-Encoding: quoted-printable
>
> Hi Folks, I now think my unidentified event was just the remainder of =
> the 5.4, not a separate event. Thanks,
> Ted
> ------=_NextPart_000_0005_01C8207B.C6AAFCE0
> Content-Type: text/html;
> charset="iso-8859-1"
> Content-Transfer-Encoding: quoted-printable
>
>
>
> charset=3Diso-8859-1">
>
>
>
>
> Hi Folks, I now think my =
> unidentified event=20
> was just the remainder of the 5.4, not a separate =
> event. =20
> Thanks,
> Ted
>
> ------=_NextPart_000_0005_01C8207B.C6AAFCE0--
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-DIGEST-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
Various of the latest list-serve comments are concerned with SNR of instruments,
so I've decided to describe a few of the things I've learned after about
two decades of intense research on the non-ideal properties of mechanical
oscillators.
To the extent that linear approximations are meaningful
(not really true at low frequencies and small
amplitudes), the theoretical description of a seismometer's performance
is straightforward, and treated
in the paper I wrote, titled "Seismometer performance based on a simple
theory of instrument-generated
noise equivalent power", online at
http://physics.mercer.edu/hpage/inep/inep.html
If you look at this paper, pay close attention to the difference
between conventional instruments that output the time derivative of mass
position (velocity) and the VolksMeter (position). Because every
seismometer (as Einstein well understood, because of inertia) responds
only to acceleration (tilt being a special case), the conventional instruments
measure the 'jerk' of the earth, whereas the VolksMeter measures its acceleration.
The two systems offer synergetic
possibilities--jerk sensors better for the high frequency range and
acceleration sensors better for the low frequency
range.
Some of the recent comments are concerned wtih noise
equivalent power generated by electronic devices. Such
noise is inevitable and temperature plays a dominant role in the electronics.
It has been understood for decades
from the time of Johnson, and its treatment is straightforward.
Insofar as temperature dependence
of the mass/spring of a seismometer is concerned, this is an entirely
different issue. A common calculation of the Brownian motion of the
seismic mass (which suggests a simple advanatage to operating at lower
temperatures) is
meaningless. The equation employed is based on the equipartition
theorem, which does not apply because the
number of 'degrees of freedom' in the non-ideal spring is much greater
than the number two that is assumed;
i.e., one term for the potential energy and one term for the kinetic
energy (each contribution one-half kT of thermal
energy), naively assuming a harmonic potential (based on Hooke's law
which is known to be not-obeyed).
For those interested in some of the foundation physics
responsible for seismometer difficulties due to mesoanelastic complexity,
I wrote the article "Anharmonic Oscillator" for the the 10th Ed. of McGraw
Hill's
Encyclopedia of Science and Technology. Typing into Google the
expression damping anharmonicity -- will return the Access Science
quote of the first part of this article. To read the whole article
you will have to either (i) pay something to McGraw Hill or (ii) contact
me and I will return a copy by email attachment.
Internal friction is intimately related to the instrument-generated
noise equivalent power and readers may find
interesting the following paper: "Harmonic oscillator potential
to describe internal dissipation", online at
http://arxiv.org/html/physics/0307016
Seismometer theory is hard enough to understand,
even when based on linear (overly idealized) approximations.
Even the professional seismologists, along with myself, have been guilty
of erroneous assumptions. I believe, after
more than a decade of trying to acquire self-consistency in at least
the linear descriptions--that I'm getting close
to a first-order approximate description that is valid for the first-cut
of instrument design. A full understanding of the real-world properties
of seismometers is truly impossible at this point in time, because we don't
understand internal friction from first principles. In the article
that I wrote, titled
"Friction at the mesoscale", Contemporary Physics vol. 45, no.
6, pp. 475-490 (2004),
I included a quote from a Nature article (Kessler) that speaks to the
matter; i.e., "It is one of the dirty little secrets of physics that while
we physicists can tell you a lot about quarks, quasars, and other exotica;
there still is no universally
accepted explanation of the basic laws of friction". As noted
in the paper, I had actually contemplated
a title "Friction, friction everywhere but in our understanding".
Randall
psn-l-digest-request@.............. wrote:
.------ ------ ------ ------ ------ ------ ------
------ ------ ------.
| Message 1
|
'------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
Subject: Re: Signal To Noise Ratio
From: "Geoff" <gmvoeth@...........>
Date: Tue, 6 Nov 2007 02:26:21 -0700
Interesting Mr. Brad Douglas;
Im not sure about any of this
but it would be nice to understand
what is in the front end of the
first PIONEER SUPERTUNERS.
I think there are very low noise devices out there
but it would be useless to use them
in any high noise environment like
ShortWave radio.
All one really needs is to keep the
combined circuit noise below the
ambient noise or you will have
a hard time seeing the those signals
riding near the natural grass.
The astronomers will supercool
their preamps to eliminate noise and
do any broadband shifting right in
the front end.
I think i would like to have
an Astronomical expert making the
electronics for my geophone
but fear I would not be able to
afford the liquid helium to
keep it in operation.
:-)
Regards;
geoff
----- Original Message -----
From: "Brad Douglas" <rez@..................>
To: <psn-l@..............>
Sent: Saturday, November 03, 2007 5:48 PM
Subject: Re: Signal To Noise Ratio
> On Sat, 2007-11-03 at 16:50 -0700, Geoff wrote:
>> Hello Bob;
>>
>> Have you ever heard of a low noise
>> GaAs op amp that is designed to work
>> like a op177G (typical opamp) or ??
>
> GaAs FETs go that low in frequency and still yield gain and stability?
> Lowest I've ever done is 144MHz and that was straining the chip,
> yielding decreased gain (but still higher than any non-GaAs FET).
If my
> understanding is correct, GaAs is "saturated" above 2GHz, making
them
> ideal for microwave LNAs.
>
> Or have I entirely missed the point? :-)
>
>> Signal to noise ratio should be easily found
>> in google I think it simply is like
>> Expectided MDL signal power / Ubiquitous Noise Power
>> The higher the ratio the better the whatever.
>> Possibly expressed in db.
>> For power thats 10Log(Sig/Noi).
>
> That's mostly accurate:
> http://en.wikipedia.org/wiki/Signal-to-noise_ratio
>
>
> --
> 73, de Brad KB8UYR/6 <rez touchofmadness com>
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html
for more information.
>
.------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
| Message 2
|
'------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
Subject: Re: Signal To Noise Ratio
From: "Geoff" <gmvoeth@...........>
Date: Tue, 6 Nov 2007 02:44:42 -0700
Hello Bob;
I guess I am no scientist because the basic
idea seems so simple to me that the signal to noise
ratio can be somewhat arbitrary in your selection
of reference points.
You pick a signal level of interest
and make sure your S/N ratio is such
you will actually see the signal of interest.
Any signal with like 6dbv X2 above the noise
should be visible. One that is 120db
is a million times the noise.
It all depends upon what noise you mean
and to me that is overall "S" noise.
White Noise. Like on an "S" meter.
As any bubblehead should know ( Sub-Sailor )
S/N is one of the sinle most important facets
of any sensor device.
I am amazed that an NMR machine can
rattle a mole of atoms in a strong
magnetic gradient and listen
to them ring With various frequencies
in response.
They must have a receiver unlike anything
I am familiar with.
I would start by looking at the USGS noise levels
then figure out what S/N ratio needs to be
before designing a serious device.
The place i live in here is so terribly
noisy I need to filter right at the
preamp to keep my electronics from
being jammed by higher vehicular frequencies.
It probably would do me little good
to invest in high class low noise
amplifiers at my current location.
The overall noise of your system
needs to be lower than the grass.
To the point of diminishing returns.
The grass being the noise in the ground
at whatever bandwidth during a quiet
sunday morning like 3am local time.
Most people do not build their own
devices and do not concern themselves
with this thought.
There are many types of noise but the only
one of interest is the overall results.
I cant wait until Universal Entropy Reaches Maximum
That will be the quietist time of all.
Regards
geoff
----- Original Message -----
From: "Bob Hancock" <carpediem1@.........>
To: <psn-l@..............>
Sent: Saturday, November 03, 2007 5:06 PM
Subject: Re: Signal To Noise Ratio
Hi Geoff -
Unfortunately, my knowledge of electronics is less than stellar.
I am
working at understanding concepts of seismology. As for
electronics.....well, I'll leave that for someone else. I was
hoping to
find an answer that would allow me to apply the SNR numbers I see to
the
practical side of seismology. I understand the simple concept
of an
amplifier (boosting a signal), but unfortunately, I have no working
knowledge of their innards or how the individual parts work by themselves
and in concert with each other.
Bob H
On 11/3/07 4:50 PM, "Geoff" <gmvoeth@...........> wrote:
> Hello Bob;
>
> Have you ever heard of a low noise
> GaAs op amp that is designed to work
> like a op177G (typical opamp) or ??
>
> Signal to noise ratio should be easily found
> in google I think it simply is like
> Expectided MDL signal power / Ubiquitous Noise Power
> The higher the ratio the better the whatever.
> Possibly expressed in db.
> For power thats 10Log(Sig/Noi).
> The noise would be the reference point.
> If you can get a 120db (coopers)
> I think youd be in fat city.
> The higher the overall s/n ratio
> the smaller signals they can see.
> Like someone sneezing next door.
>
> :-)
> geoff
>
> ----- Original Message -----
> From: "Bob Hancock" <carpediem1@.........>
> To: "PSN" <psn-l@..............>
> Sent: Saturday, November 03, 2007 1:16 PM
> Subject: Signal To Noise Ratio
>
>
> When downloading events through IRIS Wilber II, I noticed that
they listed
> the signal to noise ratio. Most of the time the number was
1; however,
> there were other numbers listed. I have some questions and
hopefully
> someone can answer them.
>
>
> 1. What is the significance of signal to noise ratio when looking
at
> earthquakes?
>
> 2. How is signal to noise ratio computed?
>
> 3. What are the ideal numbers to look for and at what point
does the data
> become unusable?
>
> Thanks
>
> Bob Hancock
>
>
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html
for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
To leave this list email PSN-L-REQUEST@.............. with
the body of the message (first line only): unsubscribe
See http://www.seismicnet.com/maillist.html
for more information.
.------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
| Message 3
|
'------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
Subject: Unknown event
From: <tchannel1@............>
Date: Tue, 6 Nov 2007 11:19:29 -0700
This is a multi-part message in MIME format.
------=_NextPart_000_0007_01C82066.E5EE6CA0
Content-Type: text/plain;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
Hi Folks, I got the 5.4 Guerrero, Mexico, here in Boise, at about
=
06:42, It was followed be another one, at about 06:52 UTC.
I can't =
identify this one? =20
Thanks, Ted
------=_NextPart_000_0007_01C82066.E5EE6CA0
Content-Type: text/html;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=3DContent-Type content=3D"text/html; =
charset=3Diso-8859-1">
<META content=3D"MSHTML 6.00.6000.16546" name=3DGENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY bgColor=3D#ffffff>
<DIV><FONT face=3DArial size=3D2>Hi Folks, I got the
5.4 Guerrero, =
Mexico,=20
here in Boise, at about 06:42, It was followed be another
one, at =
about=20
06:52 UTC. I can't identify this one?
</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Thanks, Ted</FONT></DIV></BODY></HTML>
------=_NextPart_000_0007_01C82066.E5EE6CA0--
.------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
| Message 4
|
'------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
Subject: Re: Unknown event
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= <jonfr@.........>
Date: Tue, 06 Nov 2007 18:31:27 +0000
Hi
There was a ML4.3 earthquake at 06:41 in SERAM, INDONESIA (sorry for
the
caps). Maybe it was that one ?
More details.
http://www.emsc-csem.org/index.php?page=3Dcurrent&sub=3Ddetail&id=3D69262
Regards.
--=20
J=F3n Fr=EDmann
http://www.jonfr.com
http://earthquakes.jonfr.com
http://www.net303.net
http://www.mobile-coverage.com/
.------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
| Message 5
|
'------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
Subject: Guerrero Mexico 5.4M
From: <tchannel1@............>
Date: Tue, 6 Nov 2007 13:48:56 -0700
This is a multi-part message in MIME format.
------=_NextPart_000_0005_01C8207B.C6AAFCE0
Content-Type: text/plain;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
Hi Folks, I now think my unidentified event was just the remainder
of =
the 5.4, not a separate event. Thanks,
Ted
------=_NextPart_000_0005_01C8207B.C6AAFCE0
Content-Type: text/html;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=3DContent-Type content=3D"text/html; =
charset=3Diso-8859-1">
<META content=3D"MSHTML 6.00.6000.16546" name=3DGENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY bgColor=3D#ffffff>
<DIV><FONT face=3DArial size=3D2>Hi Folks, I now think
my =
unidentified event=20
was just the remainder of the 5.4, not a separate =
event. =20
Thanks,</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Ted</FONT></DIV></BODY></HTML>
------=_NextPart_000_0005_01C8207B.C6AAFCE0--
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
To leave this list email PSN-L-DIGEST-REQUEST@.............. with
the body of the message (first line only): unsubscribe
See http://www.seismicnet.com/maillist.html
for more information.