NEW_Accomplishments.indd - IRIS

2006 IRIS 5-YEAR PROPOSAL SIGNALS AND SYSTEMS
Quality Control of GSN Sensor Response Information
Peter Davis • University of California, San Diego
The Mw 9.0 Sumatran earthquake provides a special opportunity to validate the accuracy of sensor responses. We are in
the process of comparing the consistency of free oscillation amplitudes measurements against observations of lunar tides to
investigate how accurate are the GSN instrument responses IDA reports to the community.
Shown inthe figure are observations of the M2 lunar tide and the mode 0 S 0 each normed to their respective expected values.
For the tides, the observed tide at each station was compared to that of a synthetic based upon current models of ocean
loading. For the mode, the data are expressed as deviation from the mean for the set. The consistency between the two sets
suggests that there is a problem with the published amplitude response. This is quite possible: the accepted GSN practice is to
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sor manufacturerʼs value for the generator constant.
Scatter plot of the M2 tidal amplitude deviations
vs observed 0 S 0 amplitudes at IRIS/IDA
stations during January 2005 following the
Mw 9.0 Sumbawan quake. The network scatter
for each period is higher than expected
from instrument calibrations for reasons we
are investigating.
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