Participated in seismic safety review of western US dams operated by the US Bureau of Reclamation. Calculated ground motions from near-field and far-field seismic sources in a deterministic seismic hazard analysis at various dam sites.
Estimated ground motion from a M 8.5 Cascadia subduction zone earthquake and M 6 to M 6.5 crustal earthquake sources at the site of the new state office building in Portland and the Markquam Bridge over the Willamette River. Project involved modeling finite-fault effects and equivalent-linear analysis of unconsolidated foundation soils to calculate site-specific ground motions. The earthquake scenarios were found to produce significant and potentially damaging strong motions in the metropolitan Portland area.
Estimated ground motion from a hypothetical Cascadia subduction zone earthquake for the Trojan Nuclear Power Plant. Project involved determining stochastic slip models for an offshore M 8.5 earthquake and quantification of the near-field effects of a finite earthquake source model on ground motions at the site.
Conducted a comparative analysis of non-linear and equivalent-linear soil response methodologies to determine program characteristics. Programs evaluated were SHAKE, DESRA2c, RASCAL, SUMDES, and TESS. This work involved modeling non-linear soil behavior at Treasure Island from the 1989 M7.1 Loma Prieta earthquake for the Electric Power Research Institute (EPRI). A significant result of this work was that the codes employing non-linear formulations of soil behavior performed better in modeling the response of saturated granular soils than did equivalent-linear methods. Both methodologies were found to be useful in determining the seismic response of unsaturated semi-consolidated deposits.
Conducted an analysis of strong ground motion from the 1985 M 8.1 Michoacan, Mexico, and the 1985 M 8 Valparaiso, Chile, earthquakes to determine factors influencing site-specific seismic response. Near-field ground motions were simulated using a stochastic, random vibration theory based, finite source model which incorporates the effects of dynamic and geometrical properties of source rupture, crustal wave propagation, and site-specific response. The results of this study showed that the main factors controlling modeling uncertainty at frequencies greater than 1 Hertz were near-site attenuation and frequency-dependent site response.
Attenuation relationships for peak acceleration and response spectral ordinates for ground motions resulting from subduction zone earthquakes were developed from empirical data and numerical simulations. Equivalent-linear estimates of the response of a one-dimensional soil column were used to develop attenuation relationships for soil sites. Results confirm a lower rate of attenuation for large subduction zone earthquakes compared to crustal earthquakes. The numerical simulations indicate that ground motion levels for soil and rock sites coverage in the near-field.
Synthesized geologic and seismologic data to develop a seismotectonic framework to assess seismic hazard in the Colorado Plateau. Results of this project significantly changed thinking about the tectonic environment of the region. Work was performed in support of site characterization studies for a proposed nuclear waste repository in Utah.
Conducted a study of seismicity related to solution mining operations in a flooded room and pillar potash mine. Seismicity was related not only to redistribution of stresses in a tectonically pre-stressed environment but also to fluid extraction processes which caused brittle deformation of salt.
Lake Almanor description here.
Sacramento Valley description here.