Im not sure about that Craig, In fact im not entirely sure that vibration was the issue, the pier was about 150kg empty now I guess it to be around the 300 mark I put 8 buckets of sand in it at about 20kg a bucket. What exactly has happened Im not sure...but its a good thing..
It may be just a function of added mass, putting everything under stress so that any movement firstly has to overcome the stress... dunno...