| Project Focus |
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| Accessing
Real Time Data at the IRIS DMC The
IRIS Data Management Center has primarily dealt with delayed data.
Our only effort in near-real time data is our participation in the
University of Washington SPYDER® system that provides data from significant earthquakes within a few
hours of their occurrence. During the past year we have begun developing
systems to handle data in real time for distribution to end-users.
The above figure shows the primary data repositories at the DMC.
The most familiar is of course the very large archive of continuous
waveforms in the mass
storage system. We currently have about 20 terabytes (20,000,000,000,000
bytes) of data available in the archive although its total capacity
is about 360 terabytes. We also have a collection of active source
data in SEG-Y format, older PASSCAL experimental data in miscellaneous
formats, and a wide variety of other data in variable formats (For
instance the Apollo Lunar Seismic Data Set) in the archive in what
are termed Assembled
Data Products.
The FARM is a collection
of quality controlled event oriented data sets assembled for larger
events. Historically the FARM data have been generated for only
the GSN data but the new FARM
is built for all networks the DMC receives including PASSCAL,
FDSN networks and regional networks.
The data in the FARM volumes comes from the archive.
SPYDER® data have traditionally come from near real time links
to the seismic stations such as telephone lines, autoDRM methods
or in increasing numbers Internet connections. The new SPYDER®
system is now functioning in beta mode and receives the data directly
from the new real time system at the DMC which we call the Buffer
of Uniform Data or BUD.
The SPYDER®, FARM, and BUD data all reside on large disk systems
at the DMC and thus are appropriate to provide very fast access
to data. The system provides near-line robotic access to the entire
archive but takes from a few minutes to a few hours to serve waveforms
for user requests.
The BUD is the method being developed to offer access to real time
data at the IRIS DMC. Presently we receive data into the BUD from
one of two systems: the commercial Antelope system developed by
Boulder Real Time Technologies,Inc.
(BRTT) and the Earthworm Waveserver developed by the USGS in Golden,
CO. The Antelope system supports the reception of data from 12 different
networks including the IRIS GSN (ASL and IDA), the PASSCAL Broadband
Array, GEOFON data from Potsdam, data from Patrick Air Force Base,
two central Asian Networks and several regional networks in the
United States. The Earthworm technique uses a waveserver client
developed for the IRIS DMS by ISTI.
Currently we are receiving data from the USNSN, the University of
Utah, the University of Washington and the Montana Regional Network.
Plans are to add several more regional networks using an Earthworm
client in the near future. We are also receiving data from the German
GEOFON network using a SEEDlink adapter for Antelope developed by
ORFEUS. We have plans to receive data from the GERESS array in Germany
as well.
No matter what the source of the data, all of these data flow into
the IRIS DMC’s BUD system in near real time. BUD is quite simply
a well-organized file structure with a variety of tools that can
manipulate the data within the structure. Our long term goal is
to keep approximately 6 months of each network on-line in BUD. These
data will then move from the BUD into the primary tape based mass
storage system.
An article in the next DMS Electronic Newsletter will provide greater
details on the BUD utility tools that assist in viewing data availability,
feed latency, data latency, GMT maps, waveform displays and other
such features. The focus of the remainder of this article will be
how the research community can gain access to the data in the BUD.
The figure above shows the major methods by which data can be accessed
out of the BUD system. These include:
At the present time users can access data from the BUD either by LISS or FTP. In the very near future, autoDRM access will be provided. Several clients are in the process of being developed for the Data Handling Interface and will begin appearing over the next few months. For more information about the BUD see the on-line
help pages or, for more specific access information, contact
Sandy Stromme ( Submitted by Tim Ahern For more information or comments contact |
) at the IRIS DMC.
