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 The problems that plagued the FARM were an out-of-date or incomplete accounting of station data, old or incorrect metadata headers, and data restricted to GSN stations.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:
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.