Roseville's transformation from a sleepy rail town on the Central Pacific line into a booming Sacramento Valley hub has brought a wave of high-density development across the city. As new commercial parks rise near the I-80 corridor and residential subdivisions push east toward the Sierra foothills, the ground beneath them becomes the critical variable that no amount of architectural glass can fix. The city sits on a complex patchwork of alluvial deposits from Dry Creek and Cirby Creek, with pockets of soft clay, loose sand, and weathered granite residuum that react differently during shaking. A standard site class determination often misses these abrupt lateral transitions, which is why seismic microzonation has become the backbone of rational foundation design here. Rather than relying on a single borehole and a generic amplification factor, we map the spatial variability of shear wave velocity and soil stiffness across the entire property, giving structural engineers a high-resolution picture they can actually use. This approach aligns with the 2018 update to the USGS seismic hazard model for the Sacramento region and is routinely tied to the CDC/Natural Hazards Center studies on the Roseville fault system.
A single borehole at the wrong location can misclassify an entire site; microzonation reveals the subsurface geometry that drives differential ground motion.
Our approach and scope
Local ground factors
Roseville lies approximately 30 kilometers east of the Sacramento-San Joaquin Delta, where the Great Valley sequence of sedimentary rocks and overlying alluvium can amplify long-period energy from a San Andreas rupture while also transmitting high-frequency shaking from local faults in the Foothills thrust belt. The Dry Creek and Linda Creek drainages have deposited loose, Holocene-age sands that the California Geological Survey maps as liquefaction-susceptible in Zone 2 of their regulatory maps. Ignoring the spatial distribution of these deposits is where things get dangerous: a pad graded across a former stream channel can have five feet of clean sand under the northwest footing and stiff clay under the southeast footing, and when the ground shakes, the building twists. That torsional response has been documented repeatedly in post-earthquake reconnaissance, including the 2014 South Napa event just 50 miles to the west. A thorough microzonation study identifies these compartments before the first yard of concrete is poured, letting the design team isolate the liquefiable zones with ground improvement or adjust the foundation layout to avoid them entirely.
Applicable standards
ASCE 7-22 Minimum Design Loads and Associated Criteria for Buildings and Other Structures, IBC 2024 (California Building Code adoption with amendments), ASTM D7400-19 Standard Test Methods for Downhole Seismic Testing, Caltrans Seismic Design Criteria Version 2.0, NEHRP Recommended Seismic Provisions (FEMA P-2082)
Complementary services
Surface Wave Microzonation (MASW-ReMi Grid)
We deploy 24- to 48-channel linear arrays with 4.5 Hz geophones in a staggered grid across the site, processing dispersion curves with high-resolution frequency-wavenumber and spatial autocorrelation methods. The output is a Vs30 contour map with interpolated shear wave velocity profiles every 10 to 15 meters, calibrated against downhole seismic data where available. We deliver spectral acceleration maps at the PGA, 0.2s, and 1.0s periods, along with site class boundaries per ASCE 7-22 Table 20.3-1.
Liquefaction Hazard Zonation
Using CPT tip resistance and sleeve friction data tied to the microzonation grid, we compute the Liquefaction Potential Index (LPI) and Lateral Spread Displacement following the probabilistic framework of Boulanger and Idriss (2014). The final map delineates zones of negligible, marginal, and high liquefaction susceptibility, with settlement estimates for each zone under the MCE₉ ground motion. This directly feeds into the foundation alternatives analysis and any required ground improvement design.
Typical parameters
Quick answers
What is the difference between a standard site-specific seismic hazard analysis and a microzonation study?
A site-specific hazard analysis typically focuses on a single point, often the center of the building footprint, and provides uniform hazard spectra for that location. Microzonation maps the spatial variability of site response across the entire parcel, meaning you get different spectra at different coordinates. For a Roseville site with lateral soil variability, microzonation identifies where the site class boundary actually lies, so the structural engineer can apply the correct design spectrum to each foundation element rather than using a conservative envelope for the whole building.
How much does a seismic microzonation study cost for a typical commercial project in Roseville?
For a commercial site in the Roseville area up to about 5 acres, a complete microzonation study including the MASW/ReMi grid, CPT calibration points, and the liquefaction zonation map typically ranges from US$4.380 to US$15.880. The spread depends on site access conditions, the required grid density, and whether we need to bring in a drill rig for downhole seismic calibration. We can provide a fixed-fee proposal once we review the site plan and any existing geotechnical data.
Do you need a microzonation study if the USGS map already shows my Roseville site as Site Class D?
The USGS Vs30 map is a regional proxy based on topographic slope and generalized geology; it has a spatial resolution on the order of 1 km and can miss the shallow buried channels and alluvial lenses that are common in the Dry Creek watershed. We have seen multiple sites in west Roseville where the USGS proxy indicated Site Class D but our direct measurements found Site Class E lenses at foundation depth. If your structure is Risk Category III or IV, or if it has a torsional irregularity, the incremental cost of microzonation is minor compared to the seismic performance risk of using a proxy that was never intended for site-specific design. More info.