Because the IRIS DMC manages a wide variety of waveform data from numerous network operators around the world, occasionally there is a need to re-archive data. Because this process has become fairly routine, we have begun to implement a way to document when, and why, certain waveform data get re-processed, where these are removed and replaced.
The process is initiated when data are discovered to have not met certain objective and subjective criteria that indicate that waveform data were incorrectly processed. This is most often noted by the network operator, as they are the caretakers of the data, even when they have been sent to the data archive. Reasons include incorrect compression, incomplete time series, faulty timing corrections, etc. This process emphasizes changes to the waveform data, not the information about the data, also known as the metadata. An end user may, from time to time, notice changes in the data holdings at the DMC, and for the sake of enabling more complete auditing of the various lives that data have, we hope to keep this information more in the public domain.
Now, on the IRIS page titled Data, you will see an option to “View data problems that resulted in a need for re-archiving”. The output of this database query will look something like this: