In a message dated 2006/12/03, gpayton880@....... writes:

> Another technical term that I am not familiar with has popped up: 
> EIGENFREQUENCY.  Is that synonymous with "natural period" (for our purposes)?

Hi Jerry,

       This refers to fixed period responses, due to physical 
characteristics. For instance, the Earth has a wide range of possible oscillatory modes in 
the millihertz region commonly lumped together as Eigen Modes, with various 
suffixes. The frequencies are fixed, but the amplitude of the oscillations varies 
with the exciting source and with time. The huge quake in Sumatra excited many 
modes some of which took months to die away.

       The term was first applied to characteristic optical responses of 
atoms.

       I am too embarrassed to ask the manufacturer.  Do you know the cost 
for the Lennartz seismometers?  Or, any other mfg.?  I'm just curious........

       Not off hand, but I can enquire if you like? Was there any particular 
model that you are interested in? Single axis vertical models and triaxial 
models are usually marketed. Would this be for just the sensor, or for a system 
complete with an ADC, datalogger and timing?

       New prices of 4.5 Hz geophones are about $60, 2 Hz geophones about 
$450 and 1 Hz geophones $1,000 to $2,500 depending on the model. There may be 
considerable price reductions for 2 and 1 Hz units, if you want a quantity. 

       The cost of the Guralp PEPP single vertical sensor for schools CMG EDU 
was about $4,000 when I last looked - response 30 Hz to 30 seconds. This is 
for the sensor, the ADC + electronics and GPS timing. You have to supply a PC 
computer + monitor. We can buy them at a reduced price since we do not need GPS 
timing - DCF77 timing at E10 per receiver works just fine! 

       My severe cold flu? seems to be slowly clearing up, but I am still 
feeling tired and achy. 

       Regards,

       Chris
In a me=
ssage dated 2006/12/03, gpayton880@....... writes:



Another technical term that I a=
m not familiar with has popped up: EIGENFREQUENCY.  Is that synonymous=20=
with "natural period" (for our purposes)?




Hi Jerry,



       This refers to fixed period responses,=20=
due to physical characteristics. For instance, the Earth has a wide range of=
 possible oscillatory modes in the millihertz region commonly lumped togethe=
r as Eigen Modes, with various suffixes. The frequencies are fixed, but the=20=
amplitude of the oscillations varies with the exciting source and with time.=
 The huge quake in Sumatra excited many modes some of which took months to d=
ie away.



       The term was first applied to character=
istic optical responses of atoms.



       I am too embarrassed to ask the manufac=
turer.  Do you know the cost for the Lennartz seismometers?  Or, a=
ny other mfg.?  I'm just curious........



       Not off hand, but I can enquire if you=20=
like? Was there any particular model that you are interested in? Single axis=
 vertical models and triaxial models are usually marketed. Would this be for=
 just the sensor, or for a system complete with an ADC, datalogger and timin=
g?



       New prices of 4.5 Hz geophones are abou=
t $60, 2 Hz geophones about $450 and 1 Hz geophones $1,000 to $2,500 dependi=
ng on the model. There may be considerable price reductions for 2 and 1 Hz u=
nits, if you want a quantity. 



       The cost of the Guralp PEPP single vert=
ical sensor for schools CMG EDU was about $4,000 when I last looked - respon=
se 30 Hz to 30 seconds. This is for the sensor, the ADC + electronics and GP=
S timing. You have to supply a PC computer + monitor. We can buy them at a r=
educed price since we do not need GPS timing - DCF77 timing at E10 per recei=
ver works just fine! 



       My severe cold flu? seems to be slowly=20=
clearing up, but I am still feeling tired and achy. 



       Regards,



       Chris