Data Services Newsletter

Volume 3 : No 4 : December 2001

ew2mseed - Getting Earthworm data to data centers

A New Service for Regional Networks

The IRIS DMC is currently testing a service for retrieving continuous near real time miniSEED data from Earthworm systems into the DMC’s BUD. Once in BUD, the data is immediately available for distribution in a non-QC’d form. From BUD, selected data may be QC’d and moved to the IRIS DMC’s archive.

Ew2mseed is the Earthworm WaveServerV client which retrieves the data. Ew2mseed was developed by Instrumental Technologies, Inc. (ISTI) under contract to the IRIS DMC. Ew2mseed can communicate with multiple WaveServerV’s to support high availability. Ew2mseed is the only Earthworm client capable of retrieving continuous data and writing the data to disk.

Ew2mseed robustly processes WaveServerV restarts and channel data gaps without operator intervention. At start up, ew2mseed inspects it’s BUD directory structure and files. Ew2mseed then begins requesting from the WaveServerV only data which have not yet been written to it’s BUD files. Ew2mseed requests data only if there is a good probability that the data are present. This feature helps minimize the WaveServerV load and network traffic. Currently at the DMC, Earthworm data is being retrieved from WaveServerVs run by United States National Seismograph Network, University of Utah Seismograph Network, Pacific Northwest Seismograph Network, and Montana Regional Seismograph Network. Ew2mseed is still being tested to insure it can handle problem data gracefully.

The WaveServerV/ew2mseed/BUD data retrieval process is driven by network operators who must provide the IRIS DMC with configuration files specifying WaveServerV IPs and ports and which data streams to retrieve. A dataless SEED file must be provided to the DMC and must be updated at the DMC soon after changes occur in the incoming data stream to insure all BUD functions work properly. Adequate contact information should be given to the DMC in the event of problems with the data stream. Configuration procedures are being formalized to insure that appropriate data streams will be retrieved.

This data retrieval service can eliminate or reduce the need for Earthworm network operators to write data tapes for or ftp data to the DMC. Advantages to this service over tape or ftp transfer include transfer of continuous rather than triggered data to the DMC, near real time data distribution through SPYDER®, LISS, and ftp, and Web based quality control opportunities when data is staged in BUD. An Earthworm site may need additional WaveServerV capacity to support the continuous data retrieval done by ew2mseed.

Standard Earthworm documentation and configuration guide for the ew2mseed utility is available here.

Please contact ISTI for more details about ew2mseed orw for information on how to become a data contributor.

by Sandy Stromme (IRIS Data Management Center)

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