Pyramid Geophysical Services

  • Facebook
  • LinkedIn
  • YouTube

(336) 335-3174

  • Home
  • About Us
  • Services
    • Ground Penetrating Radar
    • Electromagnetics
    • Electrical Resistivity
    • Seismic Services
    • Private Utility Locating
  • Applications
    • Underground Storage Tanks
    • Geotechnical Geophysics
    • Private Utility Locating
    • Geologic Hazards
    • Landfill Geophysics
    • Water Resources
    • Geologic Mapping
  • Case Studies
  • FAQ
  • Newsletter Archive
  • Contact
  • Pyramid Environmental
You are here: Home / Case Studies / Seismic Site Classification

Seismic Site Classification

Pyramid Geophysical Services conducted a geophysical investigation across a proposed apartment complex property in Charlotte, NC.  This survey was performed to determine average shear wave velocities in the upper 100 feet of the subsurface to provide seismic data to the client for the purposes of determining a seismic site classification. The geophysical survey consisted of performing multi-channel analysis of surface waves (MASW) seismic surveys to collect 1-Dimensional shear wave velocity profiles.

MASW shot for shear wave analysisMASW is a seismic method utilizing an array of geophones to record surface waves either as a result of an active controlled source, or natural and man-made background sources. The frequency and phase velocity of these waves is used to determine the shear-wave velocities of the underlying earth. MASW is useful in determining depths and thicknesses of soil or rock formations, determining depths of fill, and determining average shear wave velocity for seismic site classification (i.e. Vs30 or Vs100). Shear wave velocity (Vs) is also one of three generally accepted methods for determining soil or rock densities along with cone penetration test (CPT) and standard penetration test (SPT). This makes it unique among geophysical techniques.

MASW dispersion curve
Example of a dispersion curve used for MASW shear wave analysis.

Data were collected using twenty-four 4.5Hz geophones and a Geometrics 24 channel Geode seismograph.  Shear wave velocities were exported and the data were assembled into a table to calculate depth-averaged velocities. This technique allows for non-invasive engineering testing to be performed at a site, thereby characterizing the subsurface down to depths of 100+ feet rapidly and providing quantitative velocity data for site classification.

MASW Velocity Profile for Seismic Site Classification
Shear Wave Velocity Profile Used For Site Classification

 

Filed Under: Case Studies Tagged With: MASW, north carolina geophysics, seismic site classification, shear wave, Vs(100), Vs(30)

Certifications and Affiliations

GSA Contract

#gsa #contract

AFFILIATED COMPANIES

LPT Systems

Provider of lubrication, pump and tank systems and equipment, sales and service

Pyramid Environmental Services

Pyramid Environmental is our Parent Company

© Pyramid Geophysical Services Inc., a subsidiary of Pyramid Environmental & Engineering, P.C.
503 Industrial Avenue, Greensboro, NC 27406

| site by jbQ Media Web & SEO |