Shear Wave Velocity (Vs)

In seismic hazard analysis, the Shear Wave Velocity at a Site is of interest because it gives an indication of whether the expected shaking in response to an Earthquake Rupture may be higher. For instance, at a bedrock site (high shear-wave velocity) there will be little amplification of seismic waves, whereas in a sedimentary basin (low shear-wave velocity) one might expect intense amplification.

There are several ways that shear-wave velocity data is incorporated into seismic hazard calculations:

Vs30

The average shear-wave velocity between 0 and 30-meters depth. Some Attenuation Relationships require knowing whether a Vs30 value was Measured or Inferred. More information is available at the USGS Global Vs30 Map Server site

Depth 1.0 km/sec

The depth (km) to where shear-wave velocity = 1.0 km/sec (the first occurrence if more than one depth exists).

Depth 2.5 km/sec

The depth (km) to where shear-wave velocity = 2.5 km/sec (the first occurrence if more than one depth exists).