CASCADIA SUBDUCTION ZONE
The Cascadia Fault extends northwards for more than 1,000km along the west coast of North America, from northern California to midway along Vancouver Island in Canada. In 1700 the fault ruptured, generating an earthquake of around magnitude 9, which triggered a massive tsunami that was destructive even as far as Japan.
A major earthquake of a comparable size has a fair chance of happening within the next 50 years or so, leading to a potentially devastating tsunami striking the Pacific coastline of the United States and southern Canada.
Eight thousand year ago, an earthquake caused by melting of the Scandinavian Ice Sheet triggered the great Storegga landslide, off the coast of Norway, spawning a tsunami that inundated the Shetlands and the east coast of Scotland.
As Greenland’s 2-3km-thick ice cover melts at an increasingly rapid rate, the faults beneath, which have been locked under the weight of the ice for tens of millennia, will be able to move more easily. Resulting earthquakes could, in turn, trigger submarine landslides similar to Storegga, capable of sending tsunamis surging across the Atlantic.
A segment of the Sunda Megathrust Fault off the coast of Sumatra (Indonesia), which has not ruptured since 1797, is fully primed and ready to go. When it does, it’s predicted to trigger a massive earthquake – as high as magnitude 8.8 – as well as a 5-6m-high tsunami. The devastating waves will reach the Indonesian city of Padang – population close to 1 million – within 30 minutes. While some preparations are being made to counter the threat of this sleeping giant of a disaster, the chances are that the level of death and destruction will be very high.
The Puerto Rico Trench marks the join between the Caribbean Plate to the south and the North American Plate to the north. With a maximum depth of more than 8km, it forms the deepest part of the Atlantic Basin.
Submarine imagery reveals numerous giant landslides in the trench that were triggered by ancient earthquakes.
It is now more than 200 years since a major quake struck the region, and there is some concern that a future combination of a huge quake and a resulting landslide could trigger a tsunami that could be destructive across much of the Caribbean.