Real-Time Global Navigation Satellite System Positioning along Canada’s Active Coastal Margin: Efforts Directed Toward Support of Tsunami Early Warning

English Abstract:

High-rate, low-latency Global Navigation Satellite System (GNSS) data are being examined for real-time applications to monitor motions related to large earthquakes in coastal British Columbia. Specific goals for real-time regional geodetic monitoring are: collection of GNSS data with adequate station density to identify the source function for regional earthquakes with M>7.3; robust, continuous real-time analyses of GNSS data with a precision of 1-2 cm and a latency of less than 10s; and display of results with attending automated alarms and estimations of earthquake parameters. Megathrust earthquakes (M>8) are the primary targets for immediate identification, since the tsunamis they generate will strike the coast within 15-20 min. However, large (6.0<M<7.5) normal or strike-slip earthquakes when occurring within the ocean plate offshore could be mistakenly identified as large tsunamigenic events and need to be discriminated from subduction thrust ruptures in order to avoid tsunami “false alarms” and unwarranted mitigation responses.

Results from commercial software packages RTD and RTnet run in-house are compared to real-time precise point positioning streams received from other organizations. Comparison of multiple real-time solutions allows a realistic evaluation of day-to-day software performance especially when faced with adverse conditions such as data gaps or poor satellite geometry. Forward models for scenario earthquakes in this region can "fingerprint" the coseismic displacements expected from various offshore events which allows an evaluation of the effectiveness of the current regional coverage. The present distribution and density of real-time sites is sufficient for aiding the timely estimation of size, location, and nature of a great (M>8) megathrust earthquake. However, current coverage is inadequate for the unambiguous identification of the same parameters for 7<M<8 earthquakes, especially those occurring offshore northern Vancouver Island.