Hum,
I’m sure that it would have an effect.
(It may actually help in creating smaller quakes to relieve the stress build up that leads to a massive slippage though)
But it would be insignificant compared to the forces exerted along the fault lines.
On a slightly OT observation, the survey of the Ormen Lange natural gas field, in the north sea discovered the three Storegga Slides that are among the largest underwater landslides ever seen.
They occurred on the edge of Norway's continental shelf (Storegga is Norwegian for "the Great Edge"), 100 km north west of the Møre coast, where an area the size of Iceland slid, causing a megatsunami in the North Atlantic Ocean.
Sediments taken from the coastline of eastern Scotland show that a 10-meter high tsunamis flooded Scotland about 5,800 BC. At the time, Britain was joined to mainland Europe by a land bridge.
It is probable that the slide was caused by material built up during the previous ice age, and that a reoccurrence would only be possible after a new ice age.
But,
"While there is no reason for mass panic, the possibility exists that the Storegga slide will go again, and it would be imprudent to ignore that fact."
On the coast, no where is safe.
