The GSN Data Quality Initiative
During the summer of 2010, IRIS, in collaboration with the USGS/GSN, GSN Standing Committee and Networks Operations at ASL and UCSD, will embark on a review of GSN data quality and the development of new procedures for assessing waveform quality and reporting data quality issues to users. This effort is being undertaken to assure that the quality of data from the GSN is as high as possible and that the quality status of each station is openly represented to the data user community.
This review is being undertaken now for a number of reasons:
- Reports from the Lamont Waveform Quality Control Center (WQC) and studies by ASL and IDA have documented a number of significant problems with the long-period response of some of the aging STS-1 seismometers. The WQC reports also document a number of other problems with completeness and accuracy of metadata for some GSN stations. The 2010 review will carefully document these response and metadata issues and report these to the user community.
- With the completion of the major installation phase of the GSN and recent funding to recapitalize the recording equipment in the network and add secondary broadband sensors where before there were none, it will soon be possible to remotely calibrate all sensors and provide inter-sensor comparisons. Procedures are now being developed to exploit this enhanced capability to routinely calibrate and report on full instrument response.
- With the increasing similarities between the instrumentation technologies used by the GSN and other IRIS programs, especially the USArray Transportable Array, there is an opportunity to establish “pan-IRIS” metrics and procedures for tracking and reporting on data quality. Representatives from all IRIS programs will be involved in the data quality initiative and seek synergies for enhanced quality control and reporting across all programs.
A GSN Quality Assessment Team has been established, led by Kent Anderson as GSN Operations Manager, and involving members of the GSN Operations Group, the IRIS DMS and USArray. They will prepare a report on Data Quality Assessment and post information on these webpages to:
- document current waveform quality problems on a station-by-station basis
- review and correct current metadata for all stations, as necessary
- identify sources of waveform quality problems and develop timetable for correction
- review historical data to document and correct problems with metadata and response information
- develop procedures and metrics for routine quality assessment
- coordinate with other network operators to evaluate best practices
The IRIS Board of Directors has appointed an external GSN Data Quality Panel co-chaired by Barbara Romanowicz and Thorne Lay, with Harley Benz, Göran Ekström and Hiroo Kanamori as members, to:
- review existing reports on the current status of GSN data quality;
- review proposed new data quality metrics, assessment and reporting procedures;
- recommend additional actions for improved data quality control and reporting.
This Panel will meet during the summer of 2010 to review the documentation produced by the Lamont WQC and the GSN Data Quality Assessment Team and report back to the IRIS Board in the fall.
Users of GSN data are strongly encouraged to contact Kent Anderson (firstname.lastname@example.org) if they have questions about problems with the use of existing GSN data, suggestions for improvement, or other input to the Quality Assessment Team.
The following links describe the various aspects of our initiative and link to supporting documentation for this plan.
It is our intention to keep the GSN dataset of the highest possible quality and to publicly announce known problems with sensors to minimize errant interpretations of anomalous data.