Seismic Design Criteria Ground Motions

Abstract

Ground motions are derived for application to Project-specific design criteria. Both probabilistic and deterministic seismic design ground motions are developed satisfying design requirements, and using seismic source and ground motion attenuation models similar to those employed for earlier extensions to the BART system. Specifically, the Silicon Valley Rapid Transit Project (SVRT) alignment seismic design criteria for permanent structures require determination of the greater of ground motions from a site-specific 10% in 50 years (approximately, 500-year return period) probabilistic analysis or the median deterministic ground motions from the maximum magnitude events on the major active faults in the immediate vicinity: the San Andreas, Hayward, and Calaveras faults. For convenience, the continuum of design ground motion response spectra within this range were segregated into smooth enveloping horizontal and vertical surface outcrop spectra over the frequency range of 100 to 0.1 Hz and for National Earthquake Hazards Reduction Program (NEHRP) Site Class D for North, Central, and South reaches of the alignment. Based on these analyses this report defines seismic design ground motion response spectra for permanent and temporary structures for these three reaches.