Data Services Newsletter

Volume 6 : No 2 : June 2004

Virtual networks defined

Background

What are virtual networks? The IRIS DMC has introduced a new concept in accessing data from seismic stations around the globe. Seismic stations are often run by a large variety of network operators but each operator uses the same two character Network Code for all of the stations they are responsible for. Often networks are composed of several sub-networks. Perhaps a good example of a Virtual Network is the IRIS GSN. The GSN consists of stations with a large number of different station and network operators. The GSN network includes stations with network codes IU, II, IC, H2 codes everyone is familiar with but it also has selections of stations from the BK, GT, IM, MS, TS, MS and US networks.

Breakdown of the stations comprising the GSN network

Network Station Code
IU *
II *
TS PAS
BK CMB
MS BTDF
H2 H2O
GT LBTB
IC *
GT VNDA
IM ATTU
US JCT
US MIAR
US GOGA
US BLA
US WMOK

* denotes all stations

New network codes

IRIS has implemented a method allowing users to specify a Virtual Network name in place of the standard two character network code. These Virtual Networks must start with the underscore character (_) and can be up to a total of 10 characters long including the _. Users can simply indicate the network code _GSN when requesting data from all of the above stations and the IRIS DMC access tools will expand the virtual network correctly.

At the time of this publication, the following virtual networks have been defined:

VNET Code Name
_GSN GSN
_US-TA USArray Transportable Array
_US-FA USArray Flexible Array
_US-BB USArray Backbone
_US-ALL USArray all components

The primary motivation for implementing the concept of the Virtual Network at this time is to ease access to USArray data. The various components of USArray are the Transportable Array, the Permanent Backbone and the Flexible Array. The permanent array and the Transportable Array are each made up of collections of stations from existing regional networks, the former USNSN, as well as new stations funded by Earthscope. To see what stations are assigned to the different virtual networks, use SeismiQuery.

At the present time the following request tools support the concept of Virtual Networks:

  • BUD Tools
  • Direct breq_fast requests (breqfast@iris.washington.edu)
  • Dataless requests (DATALESS@iris.washington.edu)
  • WebRequest (breq_fast)

Additional request tools will be made Virtual Network capable in the near future.

by Tim Ahern (IRIS Data Management Center)

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