Data quality and validation


Data from networks FR , RA, CL, ND, MT is qualified “M” (“data center modified, time-series values have not been changed” –see voir Ahern, T., R. Casey, D. Barnes, R. Benson, T. Knight, and C. Trabant (2012). SEED reference manua, page 108), and is made available 3 to 5 days after collection by A-nodes, after having undergone the following checks:

  • data has been completed as much as possible;
  • there is no overlap, even at the sample level;
  • instrument response validity epochs do not overlap;
  • the power spectral density of the signal is in accordance with what is expected for each particular station.

Data from networks G, GL, MQ, WI and PF is made available with the quality label “Q" (“quality controlled data, some processes have been applied to the data” –see Ahern et al., 2012, page 108), and undergoes additional checks, namely:

  • waveform modeling of teleseismic earthquakes of magnitude larger than 6 through the SCARDEC method (Vallée et al., 2011) shows a good agreement between the observed and predicted signals;
  • for multi-parametric stations, the acceleration-converted seismometer and accelerometer waveforms are identical for a selection of suitable earthquakes.

Because of the complexity of these additional operations, validated data from these networks is available 6 to 12 months after its collection.

Availability of validated data from SISMOB temporary networks depends on the specificity of each experiment and generally varies between 1 and 6 months (note that SISMOB data might be under embargo for up to three years).

Ocean bottom seismometer (OBS) data may have data quality ‘D’ (times from onboard clock) or ‘Q’ (times corrected for onboard clock drift and leapseconds).  The onboard clock may drift by up to 3 seconds/year (1 second/year typical) and does not account for leapseconds. Each OBS station may have one or both qualities available for download.