This news post is an advisory to all scientists and recipients who access SEED format data from the IRIS DMC at http://www.iris.edu/
The IRIS DMC is committed to providing scientists with seismic data of high quality. We are announcing an improvement in our customized request processing which will assist with occasional overlapping data issues.This enhancement will be put into operation in the next few weeks. A new version of rdseed software might be needed.
- BREQ_FAST data requests will default to an
Mquality merged product to reduce time tears
- The DMC will begin shipping SEED volumes up to 30GB in size, (an upper limit imposed by the SEED format), where the new rdseed version 5.0 required.
- Test volumes for you to download and use for testing (if you have your own SEED software and don’t use
rdseed) can be found on http://www.iris.edu/pub/pickup
Beginning in 2002, the IRIS DMC has accepted data from recording stations in two general forms, real-time and quality-controlled. These are tagged in SEED records as
Q quality respectively. (Older data has retained the original
D designation when such distinctions were not available.)
A complication that arises is that occasionally users receive data of two separate qualities for the same time period. Depending on the software used to read the SEED data this could result in unnecessary time tears (apparent gaps and overlaps). What is needed is a way to deliver a single, post-archiving quality of data that brought these disparate waveforms together in a seamless, sample-level join. The benefit to the user will be more continuous data, enabling easier data processing and less ambiguity.
The DMC has developed procedures to create, on-the-fly, the most continuous data series possible from the highest quality data available in the DMC archive. In order to deal with the problems associated with multiple quality indicators and to differentiate these data from the SEED records supplied by the network operators, all data that has gone through this process will be marked as
M quality data (
M standing for merged). The new process for creating
M quality data is to join archival
R data at the sample level such that a continuous waveform results. The
M quality data will NOT replace the original data in the archive as we consider it of utmost importance to preserve the original recordings as delivered. Instead,
M quality will be generated dynamically and will become the default. We will always give users the option to specifically request one of the original waveform streams (
R) when desired.
Our first rollout of
M quality data will be for our BREQ_FAST email request mechanism. When users specify a
B (best), they will receive an
M quality data stream.
Though there may be some software programs that cannot read this data quality yet, users can rest assured that the most recent release of rdseed v4.8 and later can recognize and process
M quality data. Other software at the IRIS DMC has also been adapted to
Another change occurring in the very near future is that the DMC will be producing SEED volumes up to 30GB in size instead of splitting large shipments into 2GB increments. In order to use such large files rdseed users will need to upgrade to a new 64-bit version 5.0 rdseed which will be released before large shipments commence.
- IRIS DMC Operations