Quality Control of GSN Sensor Response Information

Quality Control of GSN Sensor Response Information Scatter plot of the M2 tidal amplitude deviations vs observed 0S0 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.

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 0S0 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 test DAS sensitivity upon installation, adjust the shape of the response curve using in situ calibrations, but to accept the sensor manufacturer’s value for the generator constant.


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