Anniversary of last Great Cascadia Earthquake (1700)
26 January marks the anniversary of the last Cascadia megathrust earthquake. By overlaying the shake map of the 2004 Sumatra earthquake, we can get an idea of how broad an area was shaken by this event.
Shake map from the magnitude 9 Sumatra earthquake in 2004, overlaid on the Cascadia region (Natural Resources Canada). Strong damaging shaking is anticipated to have occurred along the coast from northern Vancouver Island to northern California.
Reverse modelling by Kenji Satake of tsunami waves which hit Japan on the 27 January that year revealed that the Cascadia event was likely around magnitude 9 with a tsunami of approximately 10 metres approaching B.C.’s outer west coast.
Kenji Satake's model of the 1700 Cascadia tsunami propagating across the Pacific Ocean.
Villages along the BC, Washington and Oregon coasts were hit very hard and some were completely decimated. Researchers have since learned much about this sad event from the oral history of the First Nation People of this region.
There have also been many excavation efforts to seek tsunami deposits (layers of sand and marine material thrown upon the land by the tsunami wave) from this and previous megathrust events in the region. John Clague has done much field work toward this effort.
John Clague's photograph of a clear tsunami deposit.
Earthquake felt in BC’s wine country
A minor earthquake was felt in Penticton and other areas of the southern Okanagan region of British Columbia last night. It was well recorded on seismometers operated by the Geological Survey of Canada (part of Natural Resources Canada). While no damaging earthquakes have been recorded in this region, there have been several minor events over the years, close enough to population centres and shallow enough to be felt by numerous people.
Natural Resources Canada gathers information about how people experience earthquakes through “Felt Reports“. The perceived “intensity of shaking in relation to even a minor earthquake can indicate subtleties in subsurface conditions which influence the strength and duration of shaking of future, larger earthquakes. While similar information can be gleaned from seismic records, such data is relatively sparse in comparison to the density of earthquake reports received from people after an earthquake.
Earthquake in northeastern Ohio felt in Canada
On New Year’s eve, a magnitude 4.0 earthquake occurred in northeastern Ohio and was felt by many Canadians just the other side of the border, as well as by people throughout Ohio and Pennsylvania. As earthquakes can affect countries which share borders, such countries generally share seismic data between their earthquake research institutions. This is the case for the Geological Survey of Canada and the United States Geological Survey, which benefit from this type of collaboration frequently.