13:36 Jan 11 

Yes, thanks Chris; I was thinking earthquakes too. Your suggestion is nicely vague enough not to dismay any specialists (you seem to have a gift for those useful vague expressions that fit the bill!)

13:32 Jan 11 

Reading the blurb, this is clearly a sprung structure, which come in many forms, often (in earthquake zones) mounted on great slabs of rubber, sometimes with hydraulic dampers. Since this one is close to railway lines, the purpose would be to decouple the structure from the ground transmitting the acoustic energy. I'm no architect or structural engineer, but I can see no reason why such springs should not be made of any elastic material, rubber, steel, or composite. Here, the vague "sprung suspension system" might work, since the material of the ressort is not specified.