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.