Greetings,

Recently I add a few more channels to my system. The new event files ending
with LCZ, LCN and LCE are from the Kinematics FBA-23A I have on loan from
the USGS. This sensors is a +- 2g max 3 component strong motion
accelerometer. The new channels have a gain of 200 before the A/D
converter. The LC4, LC5 and LC7 files on my system are from the same
sensor, but with no gain between it and the A/D converter. I have been
running these channels since 6/97. All channels go through low and high
pass filtering before the A/D converter. See
http://www.seismicnet.com/rwcstation.html for more information.

By creating the new channels with the gain of 200 I have been able to
record some nice seismograms. I was even able to record the 7.7Mw Volcano
Islands event today! At first glance the raw files (their on my archive
system) appear not to have recorded this event. But if you integrate the
record, this converts acceleration to velocity, and then do a .02 hz 3 pole
high pass filter to clean up the data, you will see a very nice recording
of the event. The best file too look at is 000328a.lce. After integration
and filtering It clearly shows the P, S and long period surface waves well
above the background noise. I placed a gif image of the processed event
file here  ftp://www.seismicnet.com/000328a.lce.gif. Not bad for a strong
motion sensor. 

Now that I have the new high gain channels I don't have to wait for large
local events to get useful data out of the sensor. I would have done this
sooner but I didn't think it had the dynamic range to add more gain between
it and the A/D board. Since this sensor has a know output, it was
calibrated and refurbished at Kinematics (for free!) last year, I can use
it as a "standard" to compare it to other sensor I have on my system. 

Regards,
Larry Cochrane
Redwood City, PSN

 


__________________________________________________________

Public Seismic Network Mailing List (PSN-L)