MASW / VS30 Testing for Site Classification in Newark, NJ

A lot of sites in Newark sit on the glacially deposited clays and silts of the Passaic Formation, or on historic fill near the Passaic River and Newark Bay. These conditions make guessing the seismic site class a bad bet. We run the Multichannel Analysis of Surface Waves (MASW) survey to directly measure the average shear wave velocity in the top 30 meters, your VS30. It is a non-invasive test: we lay out a line of geophones on the ground, record surface wave propagation with a seismograph, and invert the dispersion curve to get a 1D shear wave velocity profile. The result is a defensible Site Class A through F under ASCE 7-22 and Chapter 16 of the IBC. For sites with questionable fill, where a standard SPT drilling log alone might not resolve deep velocity contrasts, the MASW method gives us a continuous stiffness profile without the spatial gaps of borehole data.

A direct VS30 measurement removes the default site class assumption and often lowers the design spectral acceleration, cutting foundation costs.

Our service areas

How we work

Newark sits in a moderate seismic hazard zone, with the Ramapo Fault system roughly 30 miles northwest of downtown. The 2020 National Seismic Hazard Model puts the peak ground acceleration for the city around 0.15g to 0.20g at the B/C boundary. That is enough that the IBC requires a site-specific VS30 determination for most projects over three stories. Our active MASW setup uses a 24-channel seismograph and a 10-pound sledgehammer source, which works well for the compact urban lots and brownfield sites common here. Because we do not need to drill, we can get a VS30 profile in a half-day, even in a fenced lot in the Ironbound district. The key output is the NEHRP Site Class, which feeds directly into the structural engineer's seismic base shear calculation. We cross-check the velocity profile against local boring logs when available, or pair it with a CPT test for a fully coupled geotechnical model.

MASW / VS30 Testing for Site Classification in Newark, NJ — Technical reference — Newark

Local geotechnical context

Chapter 16 of the IBC, as adopted by Newark's building department, mandates site classification for Seismic Design Category C and above. If a project defaults to Site Class D without a measured VS30, the structural design could be locked into a 20% to 30% higher base shear than what the actual ground conditions require. That inflates the steel and concrete takeoffs for no reason. The opposite risk is worse: soft fill or organic silt from the Meadowlands, if not detected, can put a site into Site Class E or F without the engineer knowing. A seismic refraction survey can map the top of bedrock, but it does not give you the stiffness profile within the soil column. We combine MASW with a few soundings to nail the boundary between fill and natural deposits, a critical step where the depth to the glacial lake clays varies from 10 to 40 feet across a single block.

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Email: contact@geotechnical-engineering.vip

Relevant standards

ASTM D5777-18: Standard Guide for Using the Seismic Refraction Method, ASCE/SEI 7-22: Minimum Design Loads and Associated Criteria for Buildings, IBC 2021: International Building Code, Chapter 16, NEHRP Recommended Seismic Provisions for New Buildings

Technical data

Parameter	Typical value
Test Standard	ASTM D5777-18, IBC 2021 Section 1613
Source Type	Active (sledgehammer) or passive (microtremor)
Geophone Array	24-channel, 4.5 Hz vertical geophones
Depth of Investigation	Typically 30 meters (Vs30)
Key Output	NEHRP Site Class A through F
Typical Urban Setup	Surface line, no drilling required
Reported Parameters	Vs profile, Vs30, fundamental period

Common questions

How much does a MASW survey cost for a typical Newark lot?

For a standard active MASW survey on a single-family or small commercial lot in Newark, the fee ranges from US$1,850 to US$3,280, depending on site access, line length, and whether passive recording is added.

Can you run MASW on a paved parking lot?

Yes, we can. We use steel base plates under the geophones and a metal striker plate for the hammer source. The coupling is checked on the first shot. If the pavement is thick reinforced concrete, we may need to core a small hole for the source plate, but typically the asphalt lots around Newark Avenue work without any cutting.

What is the difference between MASW and a seismic refraction survey for site class?

MASW measures shear wave velocity (Vs) directly and gives you the VS30 and site class. Seismic refraction measures compressional wave velocity (Vp) and is used to map bedrock depth and rippability. Refraction alone cannot give you a reliable Vs30 for IBC site classification. We often run both on the same spread to get a full picture: P-wave for stratigraphy, S-wave for stiffness.

Location and service area

We serve projects in Newark and surrounding areas.

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