In addition to the quality issues raised in 2010, the historic GSN dataset will be consistently reviewed to ensure that data are properly described throughout time. Through an NSF-funded effort to review seismic network quality, as a complement to their Global Centroid Moment Tensor project, the Lamont Waveform Quality Center (WQC) began to catalogue a number of GSN related data quality issues based on scaling factors between observed and synthetic seismograms and azimuth residuals that show polarization anomalies. In addition, the WQC performed 10 assessments of GSN stations that have historic quality issues. Data from these assessments as well as the 10 formal reports can be found at the WQC website. Upon review of these reports, the GSN Network Operations group wrote up a response to inform users on the state of work underway for each of these sites and the general approach to future problems. The WQC reports have been a tremendous benefit to the network operations of the GSN, as we can identify and estimate the data quality metrics for the historic record. In addition, this will give us an opportunity to review the historic metadata set along with the waveforms, to ensure the data are appropriately described through time.
