Canadian plans for participation in GSETT 3

The Geological Survey of Canada (GSC) is making preparations for Canadian participation in GSETT 3 but will be unable to make a formal commitment until the necessary resources have been secured. As Canada is expected to provide at least four alpha stations, and a significant number of beta stations, the financial resources that will be needed are substantial, even though in many respccts the GSC is, with the recent modernization of the Yellowknife array and the ongoing installation of the Canadian National Seismograph Network (CNSN), well positioned to make a significant contribution to GSETT 3. The CNSN currently (October 1993) consists of 17 broad band stations and will grow to 23 and 33 such stations by December 1993 and December 1994 respectively. Some 40 50 short period stations will complete the network. Data from all sites are continuously telemetered in real time to network acquisition centres in Ottawa and Sidney, British Columbia, archived to optical disk, and kept on line in a 72 h ring buffer. Most of the broadband sites could serve as either alpha or beta stations once the necessary software for continuous data transfer, or on request provision, of data from the selected sites has been completed. This software wili be configured so that changes in station selection are easy to implement, and this will provide considerable flexibility to the GSETT 3 planning and operations working groups in selecting the optimum network. Backup stations can be designated in the case of station failures, and the network centre in British Columbia will serve, at least for beta stations, as a backup NDC to that in Ottawa. Data from. the Yellowknife array are collected in Yellowknife and forwarded in ten minute files to Ottawa, where processing is completed and the results archived. This arrangement would not meet the deadlines for receipt of alpha station data at the IDC and new hardware and software will be needed to forward the data more immediately from Yellowknife to Ottawa. Although the procedures and formats for both alpha and beta station data have not yet been agreed upon, or even discussed, by the GSE, it is apparent that new facilities will be re quired in Ottawa to multiplex and reformat data for transmission to the IDC. We anticipate that a dedicated 56 kbaud link will be needed between Ottawa. and Washington