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Information from the test triggers and system log-files are used to monitor and report on the health of the seismic system. The test triggers confirm that the components of the sites are working and can give information regarding noise on the sensor cables. The system log-files monitor the power and communication efficiencis of the seismomenters as well as the time synchronisation between seismometers.


Some aspects of the system performance are evaluated using seismic data itself. Specific analysis of the routinely processed events make it possible to quantify the following characteristics of individual sites:

  • Triggering performance which is the ratio of events recorded by a particular site, to the events expected to be recorded by that site (with reference to triggering of other sites and the theoretical ground motion relation)

  • Level and frequency content of background seismic noise

  • Check the orientation of the sensor using the average misfit between recorded and expected direction of ground motion in P-waves

  • Site amplification/suppression effects where the spectra of observed signals in P- and S-waves and corresponding theoretical spectra (obtained using a standard Brune model of the source spectra) are compared