Seismic engineering in Pomona is not merely a regulatory checkbox — it is a fundamental layer of protection in a city where the earth's memory runs deep. This category encompasses the full spectrum of geotechnical and structural strategies required to design, analyze, and construct resilient foundations and buildings capable of withstanding earthquake forces. From identifying hidden hazards like liquefiable soils to deploying advanced energy dissipation systems, our work addresses the specific seismic risks that define the Los Angeles Basin. For property owners, developers, and public agencies, integrating these services early in a project ensures compliance, controls long-term liability, and most critically, safeguards lives and investments against the inevitable ground motions that characterize Southern California.
Pomona sits near the boundary of several active fault systems, including the San Jose Fault and the broader Puente Hills Thrust Fault, placing it within a zone of significant seismic hazard. The local geology compounds this risk: much of the city is underlain by Quaternary alluvial deposits, with shallow groundwater tables in areas near the San Gabriel Valley watershed. These loose, saturated sediments are precisely the conditions that make soil liquefaction analysis an essential step for any major construction. During a strong shaking event, these soils can temporarily lose strength and behave like a liquid, causing foundation settlement, lateral spreading, and catastrophic structural distress. A thorough subsurface investigation is the only way to quantify this threat and inform a safe foundation design.
Compliance with seismic regulations is governed by a rigorous framework of national and state codes. All projects must adhere to the International Building Code (IBC) as adopted by the City of Pomona, which mandates seismic design categories based on site class and mapped spectral accelerations. Crucially, the California Building Code (CBC), Title 24, incorporates the latest provisions from ASCE 7, including Chapter 11 on seismic design criteria and Chapter 20 on site-specific ground motion analysis. For sites with complex soil profiles, the CBC explicitly requires a site-specific response analysis, moving beyond default assumptions to develop a customized design spectrum. This is where a detailed seismic microzonation study becomes invaluable, as it maps the spatial variability of ground shaking potential across a site or neighborhood, directly informing structural loads and land-use planning.
The types of projects that demand a comprehensive seismic approach are diverse. High-density residential developments, tilt-up concrete warehouses, essential facilities like hospitals and fire stations, and infrastructure upgrades all fall under strict seismic scrutiny. A new school, for instance, must meet the additional oversight of the Division of the State Architect (DSA), which enforces even more conservative performance objectives. For critical structures or those housing sensitive equipment, a performance-based design philosophy is often employed, moving beyond life-safety to ensure immediate occupancy after a major earthquake. Advanced techniques like base isolation seismic design are no longer confined to landmark buildings; they are practical, cost-effective solutions for protecting a building's structural integrity and its contents, dramatically reducing drift and floor accelerations.
A site-specific seismic hazard analysis is a detailed study that develops a custom ground motion model for a project site, replacing the default code spectra. In Pomona, it is typically required by the California Building Code (CBC) for structures on Site Class D through F soils, or when near active faults. It accounts for local geology, basin effects, and soil amplification to provide more accurate seismic design forces.
A standard geotechnical investigation evaluates soil properties at discrete boring locations for foundation design. Seismic microzonation goes further by mapping the spatial variation of ground shaking potential, liquefaction susceptibility, and landslide risk across a broader area. This regional-scale analysis is critical for city planning, large developments, and understanding how different parts of a site will respond differently to the same earthquake.
The primary geotechnical seismic risks in Pomona are soil liquefaction, where saturated sandy soils lose strength under shaking, and seismic settlement of dry sands and fills. Additionally, ground shaking can be amplified by the soft alluvial soils in the valley. Sites near the San Jose Hills may also face potential for earthquake-induced landsliding, requiring specialized slope stability analysis.
The process begins with a geotechnical investigation to characterize the site's soil profile and groundwater conditions. Based on this, a site-specific seismic design spectrum is developed per the CBC and ASCE 7. The structural engineer then uses these ground motions to design the lateral force-resisting system. For complex sites, a peer review panel may be required by the city to verify the seismic analysis and design approach.