Pacific Engineering and Analysis is a small business specializing in characterizing strong ground motion for engineering design. We have over twenty years of experience in developing design ground motions for a variety of structures and applications worldwide. We are also extensively involved in research directed at reducing the uncertainty in ground motion prediction and incorporating research results into practice. We have developed and extensively validated methodologies to simulate strong ground motions and liquefaction susceptibility indicators in any tectonic environment that incorporates extended source effects, regional attenuation, and the effects of site specific soil columns, as well as uncertainties of these parameters. These methodologies have been used to develop design motions for over thirty critical facilities as well as numerous bridges, dams, and other structures in the western, central, eastern, and southeastern United States as well as worldwide.

           We have developed empirical attenuation relations for tectonically active regions and subduction zone sources as well as simulation based generic and site-specific attenuation relations for the central, eastern, and southeastern United States, as well as other countries.

           Recent projects include developing revised design ground motion criteria (spectra), site response analysis procedures, and an analysis time history database for the U.S. Nuclear Regulatory Commission as well as producing soil category dependent ground shaking amplification factors and extended source strong ground motions for regional, state, and city wide scenario earthquake shaking maps within western, central, and eastern U.S. regions. We have recently developed new nonlinear soil dynamic material properties based on recorded strong ground motion and quantified surface and at-depth design motions, strains, and curvatures for the high level nuclear waste repository at Yucca Mountain, Nevada. Design motions have also been recently developed for sites located in the Pacific northwest and South America for crustal and subduction zone sources.

           We are also assessing the sizes of the 1811 to 1812 New Madrid and 1886 Charleston earthquakes using relict liquefaction information and extended source simulations. Liquefaction susceptibility indicators incorporated into the extended source simulations include cyclic stress ratio, strain energy density, and Arias intensity. Variabilities in source, path, and site properties are naturally accommodated in the liquefaction indicators. Results of the simulations are being used to develop attenuation relations for the liquefaction indicators as functions of magnitude and distance, directly incorporating uncertainty in source, path, and site processes.

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