Vancouver Island Won't Sink. Its West Coast Will Drop Up to 2 Metres.

Vancouver Island won't sink. Its west coast will drop up to 2 metres in the next megathrust earthquake, by Natural Resources Canada's explanation, and nobody can give you the date. Since 1991, GPS instruments anchored into bedrock along this coast have measured the outer coast moving northeast by more than 10 mm a year. In the summer of 1999, seven of those stations briefly moved the other way, and geophysicist Herb Dragert and his colleagues found a fault slipping without an earthquake anyone felt. This is the documented story of a coast that looks still: what the GPS network measures, the locked plate boundary offshore, the shift and the drop expected in the next great earthquake, the 1700 earthquake, the slow slip of 1999, why an average interval is not a deadline, the onshore earthquake of 1946 and the seconds an early warning can buy. In this video: Since 1991: GPS instruments anchored in bedrock; outer coast sites moving northeast by more than 10 mm a year, relative to an inland reference near Penticton Offshore, the Juan de Fuca plate descends beneath the North American plate; a locked section resists and the crust deforms Expected in the next great earthquake: the outer coast of southern Vancouver Island moves as much as 5 m southwest, and the west coast drops by as much as a metre or two; two directions, not 7 m of sinking January 26, 1700: a magnitude 9 earthquake, rupture roughly 1,000 km from mid Vancouver Island to northern California; the Cowichan people's houses collapsed; the tsunami destroyed the Pachena Bay people's winter village, as Chief Louis Nookmis told it in 1964; records of the tsunami in Japan fixed the timing; the outer coast dropped and drowned marshes and forests Summer 1999: seven GPS sites reversed direction for six to fifteen days, by 2 to 4 mm; Dragert, Wang and James, 2001: about 2 cm of slip 30 to 40 km down, a seismic moment equivalent to a magnitude 6.7 earthquake, over weeks, and nobody felt it 2003: slow slip linked to weak tremor; episodic tremor and slip; the deep fault sticks for about fifteen months, then slips several centimetres over a couple of weeks; it does not help predict earthquakes Thirteen great earthquakes in 6,000 years, one every five to six hundred years on average, as close together as 200 years and as far apart as 800; an average is not an appointment The USGS: no scientist has ever predicted a major earthquake; only probabilities over years June 23rd, 1946, 10:13 am: magnitude 7.3 in the Forbidden Plateau area, west of Courtenay, Canada's largest historic onshore earthquake; 75% of the chimneys down in Cumberland, Union Bay and Courtenay Spring 2024: Canada's earthquake early warning system begins operating in British Columbia; seconds to tens of seconds of notice Drop, Cover and Hold On; long strong shaking, or a rapid rise or fall of the water, is the warning: get to higher ground and stay until the all clear Key figures: more than 10 mm a year on the outer coast; up to 5 m southwest and a metre or two down in the next great earthquake; 13 great earthquakes in 6,000 years; and 2 cm of slip in 1999 that nobody felt. Timeline: 1700 to 1946 to 1991 to 1999 to 2001 to 2003 to 2024. 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Three quantities are kept apart as the sources keep them: the measured motion, the expected shift and the expected drop. Living persons are described by their published work and the official record only. Subscribe and turn on notifications. Tell us in the comments: if you could add one layer to a map of Vancouver Island, which would you choose: the measured ground movement, the evidence of the last great earthquake, or your local tsunami evacuation zone? #Canada #Geography #VancouverIsland #Cascadia #Earthquake #Tsunami #BritishColumbia #JuanDeFuca #GPS #Megathrust