Seismology in the City

Estimating Vs30 (the average S-wave velocity to 30 meters depth) requires the collection of data to measure soil and rock velocities. The traditional method for collecting these S-wave velocities required drilling a borehole and logging S-wave velocities down the well. Many newer methods have been developed to estimate Vs30 without requiring borehole drilling and logging. One of those methods, shown above, uses ground "thumps" to get soil layer thicknesses and S-wave velocities for calculating the Vs30 at a site.