Virtual Networks at the DMC

Overview ¶

A virtual network is a group of stations representing an affiliation that goes beyond the traditional bounds of networks to represent an umbrella organization or initiative. A virtual network definition allows the arbitrary grouping of stations each with independent time ranges. Virtual networks are identified by a virtual network code. To differentiate virtual network codes from traditional FDSN/SEED network codes virtual network codes are prefixed with an underscore _ character. Most of the EarthScope DMC’s public access tools allow users to query for and access data based on virtual network codes.

A good example of virtual network utility is the Global Seismographic Network (GSN) which is a collection of more than 220 stations from over 10 different networks. Data and information about these stations as a group is accessible using the _GSN virtual network code.

For further discussion of virtual networks at the EarthScope DMC refer to the following DMS Electronic Newsletter articles:

• Virtual Networks – Volume 6, Number 2
• Virtual Networks becoming a reality at the DMC – Volume 6, Number 3
• Virtual Networks at the EarthScope DMC – Volume 8 Number 4

Virtual Network Discovery and Browsing ¶

• MetaData Aggregator includes a list of public virtual networks (below the traditional networks) in expanded form and combined with station metadata.
• Programmatic Access Both virtual network definitions and resolved listings are available from the DMC’s virtual network web service.

Virtual Network Description (VND) ¶

A virtual network is defined using a Virtual Network Description (VND) which contains a list of network-station pairs each with independent start and end times.

Each unique primary and secondary data center affiliation code must be included in a VND and indicate a URL to the given data center. As an example the VND for the GSN is easy obtained in comma-separated value (.csv) format using the virtual network web service: _GSN VND in comma-separated value format

Virtual Network Description Maintenance

The recommended way to update (or create) a VND is to download a current VND from the virtual network service, edit as needed and return, usually by email, to the DMC. Note: the DMC will only load pre-approved VNDs.

Important points regarding maintenance ¶

• A VND completely defines a virtual network, there are no partial updates.
• The required fields are: virtual network, network, station, start date, start time, end date and end time, all other fields are optional.
• The station field may be * to indicate all stations from the network.
• The date fields are in YYYY/MM/DD format and the time fields are in hh:mm:ss format.
• Any primary or secondary codes must be accompanied by matching DCC: lines indicating a URL for the data center.
• Only lines starting with a virtual network code or DCC: are parsed from the VND, all other lines are ignored. The virtual network service output includes more lines for informational purposes only.

VNDs can be submitted to the DMC in either MS-Excel (.xls) format or comma-separated value (.csv) format. XML-based MS-Excel formats, i.e. with a .xlsx extension, are not supported.