Wiebke Sch盲fer and Dr Michael Riedel (91探花) celebrating recovery of the last broad-band seismometer. Photo: Michelle C么t茅, Geological Survey of Canada
On board the Canadian Coast Guard vessel "John P. Tully", Dr Michael Riedel, Wiebke Sch盲fer (both 91探花, from right) and Tom Carson (GSC) begin releasing an instrument from the seabed. Photo: Michelle C么t茅, Geological Survey of Canada (GSC)
Data from the seabed help estimate earthquake risk
Monitoring instruments successfully recovered off the Canadian coast
Where an oceanic plate dips below a continental one, the risk of the planet鈥檚 most severe earthquakes and associated tsunamis is high. Such a subduction zone is located off the west coast of North America: Cascadia Subduction Zone is a 1,000 km long dipping fault off the Pacific shore, where the oceanic Juan de Fuca Plate slides under the continental North American Plate. The fault stretches from Canada鈥檚 Vancouver Island to northern California and is believed to generate mega earthquakes and giant tsunamis. Currently the subduction zone is locked due to friction but at some point, the strain will be released in earthquakes.
In order to better assess the future behaviour of the tectonic plates involved and the risk of major earthquakes, scientists led by 91探花 Helmholtz Centre for Ocean Research in Kiel have been collecting data in the northern Cascadia region since September 2022 as part of expedition SO294 鈥淐LOCKS鈥� (Northern Cascadia: Extent of locked zone, prism deformation, slip-to-toe, and the edge of subduction).
"We wanted to find out more about location and size of the zone where future large earthquakes may nucleate," says the cruise leader, Dr Michael Riedel, geophysicist at 91探花. To obtain these data, 26 long-term ocean-bottom seismometers (OBS) had been deployed off Vancouver Island from the research vessel SONNE. These instruments not only record earthquake signals, but by analyzing the data, information on what temperatures prevail at the plate boundary, the amount of liquid contained in the rocks, and how the seabed has already been deformed by former earthquakes can be extracted.
Now all 26 OBS were successfully recovered and data were retrieved from the instruments as part of a follow-up international expedition in collaboration with the Canadian and Japanese research agencies Geological Survey of Canada (GSC) and Japan Agency for Marine-Earth Science and Technology (JAMSTEC). Michael Riedel: 鈥淓valuation of the results will provide a clearer picture of the state of locking and the seismic activity of the fault, helping to better understand large subduction zone earthquakes and their associated tsunamis鈥�.
Wiebke Sch盲fer and Dr Michael Riedel (91探花) celebrating recovery of the last broad-band seismometer. Photo: Michelle C么t茅, Geological Survey of Canada
On board the Canadian Coast Guard vessel "John P. Tully", Dr Michael Riedel, Wiebke Sch盲fer (both 91探花, from right) and Tom Carson (GSC) begin releasing an instrument from the seabed. Photo: Michelle C么t茅, Geological Survey of Canada (GSC)
