 FARM,
the Fast Archive Recovery Method
The IRIS DMC recognizes the fact that the most interesting data,
and most frequently requested, are data from earthquakes. Most of
these interesting events are larger than a magnitude of 5.5. For
this reason, the IRIS DMC routinely pre-assembles data from earthquakes
that are larger than 5.7, unless the event depth is greater than
100 km, in which case we include those down to 5.5. Although IRIS'
mission is to protect the entire archive of continuous data, event-related
data holdings are the most valuable and frequently accessed.
An intiative was put forth in the Summer of 2000 to rebuild the
FARM system. The problems that plagued the FARM were an out-of-date
or incomplete accounting of station data, old or incorrect metadata
headers, and data restricted to GSN stations. The goal was a system
that could more easily be updated as station data became available
from many networks, and where updates in station metadata would
not require time-consuming rebuilds of thousands of SEED
files. The result was a design called "POND", which is
an acronym for "Pool Of Network Data". The scheme would
involve breaking the FARM data into pieces, each of which could
be easily modified or appended to as needed. (One POND holds all
the data for one seismic network.) For more about POND, please read
this DMC
Newsletter Article....
Accessing FARM data can be done in two ways:
- WILBER II - a Web interface
for browsing and requesting event related data. WILBER allows
you to group networks together into one file or several files,
depending on your chosen output format. This is by far the preferred
method for requesting FARM (and SPYDER®)
data.
- FTP
- users can download miniSEED files directly from the network
PONDs but they will have to get the dataless SEED volumes that
go with these data only files. (Learn more about getting
dataless SEED...)
The POND structure is as follows:
/<year>/<month>/<event_date.farm>/<network_code>/miniSEED.<network_code>
The miniSEED file in each network folder contains all the data
for all the stations in that network that returned data for that
event. (Learn more about miniSEED
data files...)
UV FARM
The UV FARM is an online data repository for the Ultra
Long and Very
Long period seismic data. Because of their low sample rates
and small data volume, we prefer to service requests for these
data from our WILBER II interface, and bypass the need to recall
these from our near-line, tape-based mass storage filesystem.
What you find in the UV FARM are month-long miniSEED volumes,
delimited by the networks which contributed them.
Because these data are managed by the typical FARM algorithms, you can
be assured that the data are up to date,
as they are consistently modified if new or replacement data come online.
As a data user, you have the ability to request any, or all, reporting
channels that were collected for the time period of interest. One
important difference in the interface for requesting UV FARM data from
the typical, event-based FARM data, is that we do not provide the
mechanisms to time window these holdings below the one month time span.
You will have the ability to pull data back from these holdings in
the same number of data formats, including miniSEED, fullSEED,
and SAC.
The IRIS DMC began building the UV FARM in the summer of 2002,
and we
are able to provide data back to June, 1975. This project will continue
until we get to one month behind real time, then each month we will
automatically make the most current data available in a rolling
time window. |
