OLE and CLE definitions OLE and CLE definitions rainandcm (Geotechnical) (OP) 17 Nov 15 01:00 How to determine the return period of OLE (Operating Level Earthquake) and CLE (Contingency Level Earthquake)? Do they vary based on different types of projects? Thanks. RE: OLE and CLE definitions Agent666 (Structural) 21 Nov 15 01:32 I'm not familiar with the specific terminology you are using, but in most codes dealing with a probabilistic method of assessing the risk of an event occurring within a certain period, it will depend on the design life of the structure (i.e. 5 years vs 100 years for example) and the 'importance' of the building (i.e. consider an airport vs a residential house for example). So yes the return period will more than likely vary based on different types of project.