Seismic site assessment in San Bernardino addresses the critical need to characterize ground behavior in one of California's most seismically active regions. Located within the interplay of the San Andreas and San Jacinto fault systems, the area demands rigorous investigation compliant with CBC Chapter 16 and ASCE 7-22 standards. Our approach begins with targeted geotechnical investigation to define the subsurface profile, explicitly evaluating liquefaction potential, cyclic softening, and seismic settlement. We integrate site-specific probabilistic seismic hazard analysis (PSHA) using USGS Unified Hazard Tool data to establish design ground motions, ensuring every project meets California Geological Survey (CGS) special publication 117 guidelines for fault rupture avoidance and dynamic soil characterization.
Our field methodology relies on standardized In-Situ to capture fundamental soil parameters required for seismic design. We deploy cone penetration testing (CPT) to produce continuous high-resolution logs of tip resistance and sleeve friction, enabling direct correlation to liquefaction susceptibility per Robertson (2022) methods without sample disturbance. Complementary standard penetration testing (SPT) provides index samples and N-values for established simplified procedures by Youd et al. (2001) and Idriss & Boulanger (2008). For projects requiring advanced small-strain stiffness profiling, we supplement with In-Situ such as seismic CPT or crosshole surveys. These methods conform to ASTM D5778, D1586, and D4428 respectively, generating defensible data for both equivalent-linear and nonlinear site response analyses.
Typical San Bernardino projects demanding this level of seismic rigor include logistics centers near San Bernardino International Airport, bridge replacements along I-215, and essential facilities like hospital expansions. For shallow foundations on potentially liquefiable alluvial deposits, we often specify field density testing using the sand cone method to verify compaction of engineered fills designed as mitigation. Deep foundation evaluations for overpass structures frequently incorporate flat dilatometer testing (DMT) to refine constrained modulus profiles, while critical lifeline projects may require Ménard pressuremeter testing (PMT) for direct measurement of in-situ lateral stress and deformation modulus. When intact soil structure is essential for dynamic laboratory testing, we perform undisturbed sampling with Shelby tubes following ASTM D1587, handling specimens with strict chain-of-custody for resonant column or cyclic triaxial testing.
We deliver a comprehensive geotechnical seismic report that moves beyond parameter compilation to provide clear, actionable design recommendations. The process synthesizes field data, laboratory results, and engineering analysis into specified ground motion response spectra, site class determination per ASCE 7-22, and quantified liquefaction-induced settlement estimates. Deliverables include seismic hazard deaggregation, liquefaction potential index maps, and earth pressure diagrams incorporating seismic increments. This rigorous, defensible framework directly supports structural engineers in achieving code-compliant, resilient designs while proactively managing the subsurface risks inherent to building in the Inland Empire's dynamic tectonic setting.