Hi Geoff,

I have to admit you're a tough one.


About metrology;

Calibrating a thermometer to an accuracy of +/- 1 degree so you can
measure the temp of baby formula can be done in most any kitchen and no
one can argue that it is not calibrated. 

Calibrating seismographs is much the same, it just does not have to be
that accurate. A few parts per thousand is good enough and that is
within the reach most anyone that can build a home seismometer.  I was
calibrating a sensor during a class and sweating the decimals and the
instructor said to calm down, +/- 5% was fine.

He asked me to image setting off a firecracker at one end of a pile of
construction ruble and sensing it at the other end with a very accurate
sensor and one that was not so accurate and trying to say much about the
pile of ruble or nature of the firecracker with either sensor.

About amateurs;

Being an amateur has very little if anything to do with the quality of
what is being done. In it's simplest context it just means you don't get
paid for doing what you do. Many amateur do great work and in some cases
better work than paid professional.  Paid professional and scientist
have to be concerned about the bottom line and us amateurs can ignore
that reality.  I think you would be surprised that many amateurs are
building seismometers that are just as good as what the professionals
build, and better than some, and I will add if you can calibrate and
keep the temperature constant then the data from any seismometer is good
data. 

About IRIS

Yes, you can send raw data to IRIS along with the calibration file and
they will make a power density function display for you, but you will
need the calibration file.  IRIS knows nothing about your seismometer
and the calibration file allows them not to care.  That's what the
calibration file is about, not caring about the sensor and it's
associated electronics.

Geoff, I have no doubts that calibrating a seismograph is well within
your abilities.  I will add that if all you care about is picking phases
(P and S and their variants) then calibration is not an issue.  And for
small local earthquakes you can use the duration or coda to determine
magnitude (Mc or Md) so you have no need for calibration, it does not
matter.  And if you had a bunch of sensors like that and some decent
timestamping of the data then you could locate epicenters.  

Regards,

Angel




__________________________________________________________

Public Seismic Network Mailing List (PSN-L)