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Interactions Between the IRIS Data Management
System and PASSCAL Programs
Twenty years ago, few people anticipated the present scope
of PASSCAL’s data-generation capabilities. Instead of being
dominated by active-source data sets in SEGY format, the
PASSCAL facility has evolved into one largely dominated
by broadband data collected during dozens of multiyear
experiments led by numerous PIs. Proper archival of data
and metadata for the long-term benefit of the community is
obligatory for essentially all science-driven uses of PASSCAL
instrumentation, and requires substantial interaction
between PASSCAL and the IRIS Data Management System.
Data Availability
Permanent archival of broadband data from PASSCAL
experiments is now routine and relies heavily upon close
coordination between the PIC and the IRIS DMC in
Seattle. SEGY data sets from active-source experiments also
continue to routinely flow to the DMC (Figure 31). PIC personnel
performs all front-line quality control on PASSCAL
data and metadata.
At the end of 2007, the IRIS DMC had 2.22 terabytes of
assembled PASSCAL data archived and 14.97 terabytes of
broadband data available in SEED format.Total PASSCAL
Archive Size (terabytes)
80.0
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
Jan-92
Jan-93
Jan-94
Jan-95
Jan-96
IRIS DMC Archive Growth
Single Sort
January 1, 2008
Jan-97
Jan-98
Jan-99
Figure 31. PASSCAL data form one of the largest data volumes at the
IRIS DMC, second only to US regional networks.
Jan-00
Date
Jan-01
Jan-02
Jan-03
EarthScope
PASSCAL
Engineering
US Regional
Other
JSP
FDSN
GSN
Jan-04
Jan-05
Jan-06
Jan-07
Jan-08
DMC holdings are now approximately 25% of the DMS
archive—roughly 30% more data than the IRIS GSN archive,
and include data from 3,862 PASSCAL stations in its archives.
A key feature at the DMC is that its various request tools
can generate requests for SEED-formatted data volumes
for users regardless of whether those data were collected by
the GSN, FDSN partners, US regional networks, USArray,
or PASSCAL. For instance, a simple query procedure using
the jWEED program allows a user to draw a region on a
world map and request all broadband data collected within
that box. This was not originally anticipated as a capability
when IRIS was originally formed, but now allows for the
seamless use of the worldwide broadband data resource by
the broad community.
PASSCAL Data Distribution
GSN data are the most frequently requested single data
source at the DMC, but the amount of distributed PASSCAL
data is also very large (Figure 32). The annual request rate
is also accelerating for both data sets with a doubling time
of approximately two years. Data volume requested from
PASSCAL sources is currently more than one-half of that
requested from GSN sources (e.g., 9.9 terabytes total as
compared with 18.4 terabytes for the GSN). Although the
Transportable Array is in many respects the most exciting
new data source in seismology, total shipments from
PASSCAL experiments currently still exceed data shipments
for the Transportable Array (9.9 terabytes as compared to 7.4
terabytes) and only last year did more data ship on an annual
basis from the Transportable Array than from PASSCAL (3.8
terabytes from the Transportable Array as compared with 3.4
terabytes for PASSCAL).
Support for Assembled Data from Controlled
Source Seismic Experiments
The PASSCAL Instrument Center continues to improve
support for SEGY format data. Over the past two years,
PASSCAL and the DMS have developed a system based
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