Ah, yes- nature of the ground and quality of construction. Much of my community is built on marine sediments, susceptible to liquefaction (buildings may sink into the ground when shaken). The local hospital is building an extensive addition and a major part of the project has been digging a mammoth hole and preparing the extensive subfoundation - as I understand it, a mammoth concrete plug on which the foundation will be placed - all to counter the effects of potential liquefaction.