Dear MUSTANG Users,
It has come to our attention that the MUSTANG timing_quality metric has been calculated with a slightly different algorithm than the intended method in its description. The timing_quality metric should r eport the daily average of timing quality values stored in SEED Blockette 1001. Instead, it has been reporting the sum of the Blockette 1001 values divided by the number of miniSEED records, under the assumption that the number of records is equal to the number of Blockette 1001 values. While this is often a good assumption, some digitizers used by the IU network prior to 2015 did not record Blockette 1001 values for the first and last record of the day, resulting in slightly lower timing_quality values than intended. This issue may also affect other networks and other times.
We have corrected the code for the timing_quality metric so that it will correctly calculate the average of the Blockette 1001 timing quality values per day as described in [
http://service.iris.edu/mustang/metrics/docs/1/desc/timing_quality/ |
http://service.iris.edu/mustang/metrics/docs/1/desc/timing_quality/ ] . All new calculations of the metric going forward will report the correct values and we will be re-calculating the metric back through the archive for days that recorded values greater than 0 or less than 100. This criteria should cover all instances where the number of records may be different from the number Blockette 1001 values. The number of days potentially affected by this issue represents ~10% of our archive and it may take several weeks to recalculate.
Best Regards,
Gillian Sharer
IRIS DMC
gillian@iris.washington.edu
