OGD - STATION INSTRUMENTATION

1.High-Gain Long-Period Seismograph System-HGLP:  [HG]

Dates of Operation:   28 Dec 1973 to 29 Jan 1979.	

SEISMOMETER TYPE:
Teledyne-Geotech long-period 3 component system, Model S-11 vertical and two  
Model S-12 horizontals.  Seismometers are located in sealed metal tanks filled  
with argon gas.

DIGITAL FORMAT:
16 bit integer data words for all components.  Range: +32767 to - 32768 counts.

EVENT DETECTOR ALGORITHM:  None.

Click on any of the following items for further information

• Channel Data
• Amplitude Response to Ground Motion
• Seismic Noise Study graph information
  • Seismic Noise Level - Annual
  • Seismic Noise Level - Seasonal/Diurnal

COMMENTS:
The HGLP Seismograph Network was the first global network of digitally recording   
seismograph stations.  Installations began in August, 1972, and the last system 
was closed in 1979.  The initial hardware included long-period phototube amplifiers
(PTA) which had inherent drift problems which in turn affected the calibration.  The
PTAs were replaced with Ithaco amplifiers in early 1975 which resulted in a standard
response curve for the HGLP Network.  All of the data was recorded on 7 track magnetic 
tape.  In 1985 all of the HGLP data was rerecorded on 9 track magnetic tape in SRO 
format.  This data is now available in the SEED format, however, it should be noted  
that the calibration for much of the data is suspect.

The Ithaco amplifiers were installed at OGD on 22 Jan 1975.