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Seismic hazard: analysis and design of large ground-based telescopes

This paper will discuss analysis and design of large ground based telescopes for seismic hazard. Seismic hazard is an important issue for both the observatory and the telescope structure. Properly defined seismic specifications are vital. These specifications should include performance objective that matches performance levels and probabilistic based hazard levels for operational and survival conditions. The paper will discuss specific tools that utilize results of existing seismic hazard assessment programs and can be used for initial seismic assessment during site selection. In the final stage of site selection, site specific probabilistic seismic-hazard studies that account for local geological settings and active faults should be used. The results of these site specific studies usually include response spectra and time history records in horizontal and vertical directions for operational and survival conditions. Different methods to analyze the telescope structure for seismic loadings, such as, equivalent static analysis, response spectrum analysis, linear and nonlinear time history analysis, are discussed. Devices that mitigate seismic forces and/or deformations are also presented.