Last Updated Tue, 13 Sep 2005 21:53:36 EDT
Vancouver Island is moving west - not a lot - but every 14 months it moves 5 millimetres toward Japan in what seismologists call a tremor and slip event.
The slipping and sliding movements are equal to an earthquake of 6.5 to 6.7 on the Richter scale, but instead of happening in 10 seconds, it takes about two weeks.
Scientists used GPS satellite positioning to measure the westerly movement.
Seismologist John Cassidy of the Pacific Geoscience Centre in Sidney, B.C., said they connected that movement with a type of seismic grinding of the ocean plates and discovered the tremor and slip event. "This new information is allowing us to better understand where these earthquakes occur, and how large they can be, and how the ground will shake."
Cassidy said Tuesday: "We think that it's one of these events that will trigger the big mega-thrust earthquake. We just don't know which one of these events will trigger the giant earthquake."
Experts at the federal government agency on Vancouver Island are talking with seismologists around the world, trying to develop connections between the devastating Indonesian earthquake last year and the tremor. There was only one seismic station operating near Indonesia at the time and they're trying to get the data from that station.
Cassidy said scientists may be able to use the new tremor and slip model to predict ground shaking and develop safety models. "To protect ourselves from future earthquakes we need a good building code. We need buildings to be designed to withstand the level of shaking we would expect. We just want to be prepared."
Cassidy said they will likely never be able to accurately predict when and where a quake would happen.
The Cascadia subduction zone runs beneath the waters off Canada's West Coast, large earthquakes of a magnitude nine or more occur there about every 500 years. The last major quake in that zone was Jan. 26, 1700.
A similar subduction zone, where an ocean plate pushes beneath a continent, runs along Indonesia.