The Storegga Slide was a catastrophic underwater landslide that occurred off the coast of Norway about 8,200 years ago. This YouTube clip shows simulations that indicate that this slide resulted in landslides in the 10's of metres across the surrounding shorelines, including the Norwegian coast, Greenland, Iceland, Shetlands, Orkneys, Britain etc and by several accounts, it wiped out the now submerged North Sea land-bridge known as Doggerland.
A possible cause from the Wikipedia article (linked above) is:
A likely triggering mechanism is thought to be an earthquake causing a catastrophic expansion of methane hydrates.
This earthquake scenario is also mentioned in this YouTube clip.
What evidence is there of a seismic trigger of the Storegga Slide?