Fullerton sits on the eastern edge of the Los Angeles Basin, where the Raymond Fault and Puente Hills thrust system create complex subsurface conditions. With a population exceeding 140,000 and elevations ranging from 100 to 800 feet above sea level, the city demands rigorous geophysical investigation before any mid-rise or critical infrastructure project. Seismic tomography using both refraction and reflection methods provides the 2D velocity models needed to identify buried fault zones, bedrock depth, and potential liquefiable layers. Coupling this with a response seismic analysis gives engineers the full picture for ASCE 7 site classification.
Refraction tomography maps bedrock geometry; reflection tomography resolves stratigraphic detail. Together they deliver a continuous velocity model unmatched by boreholes alone.
Methodology and scope
Local considerations
Fullerton sits within Seismic Zone 4 under the Uniform Building Code, with peak ground acceleration values of 0.5g or higher. The city is underlain by the Puente Formation—a mix of sandstone, siltstone, and claystone—overlaid by young alluvium in the floodplains of Coyote Creek and Brea Creek. These unconsolidated deposits can amplify ground motion by a factor of 2 to 3 compared to bedrock sites. Without seismic tomography, designers risk underestimating site amplification or missing a fault crossing the property. A single 2D velocity profile can reduce uncertainty in the site class determination and save thousands in over-designed foundations.
Applicable standards
ASTM D4428-19, ASCE 7-22 (Seismic Load Provisions), IBC 2021 (Chapter 16), California Building Code (CBC) 2022
Associated technical services
Refraction Seismic Tomography
Uses first-arrival travel times from P-waves to build a velocity model of the subsurface. Ideal for determining bedrock depth, identifying fault zones, and mapping the top of the Puente Formation in Fullerton's hillside areas.
Reflection Seismic Tomography
Resolves thin layers and stratigraphic boundaries by analyzing reflected wave arrivals. Used where alluvial fill overlies bedrock or where buried channels exist beneath Coyote Creek floodplains.
Typical parameters
Frequently asked questions
What is the difference between refraction and reflection seismic tomography?
Refraction tomography measures the travel time of waves that bend through velocity layers, mapping large-scale structures like bedrock depth. Reflection tomography captures waves that bounce off boundaries between layers, resolving thin beds and stratigraphic details. In Fullerton's alternating sandstone and siltstone sequences, both methods complement each other.
How deep can seismic tomography investigate in Fullerton's soils?
With a 48-channel spread and a sledgehammer source, we typically achieve depths of 30 to 50 meters. In areas with stiff Puente Formation near the surface, depth may extend further. For deeper targets, an accelerated weight drop or explosive source can push the investigation beyond 60 meters.
How much does a seismic tomography survey cost in Fullerton?
Costs typically range between US$2,450 and US$6,000 depending on line length, number of profiles, and site accessibility. A single 48-channel line with basic processing falls at the lower end; multiple lines or reflection processing push it higher. Contact us for a project-specific quote.