GEOMETRICS
Dr. Hayashi’s work is focused on seismic hazard analysis, particularly the average S-wave velocity to 30m depth (Vs30). Estimating Vs30 is an important proxy for determining the ground’s behavior in response to shaking. In general, lower Vs30 values correlate to greater wave amplification and thus to greater damage potential. However, Vs30 estimates have their drawbacks, such as time-consuming set-up, specific space and ground-conditions, and a large investment in equipment.
This most recent work is focused on using a different measurement – the horizontal-to-vertical spectral ratio (H/V) – to predict Vs30 values. This measurement is faster and easier to obtain than the more typical Vs30 measurement. For example, a standard technique surveyors use to collect Vs30 measurements is to place a linear array of 24 sensors along a 100m line and then gather active or passive shear wave measurements. In comparison, a scientist can use a single, 3-component sensor, such as the Atom-3C, to collect the data required to evaluate seismic risk.
To produce the predicted Vs30 value, Dr. Hayashi input the H/V spectral values along with the relevant geographic coordinates and general geomorphological information into a supervised machine learning environment. The predicted Vs30 values derived from the data inputs are generally consistent with Vs30 values that are measured directly.
What does this mean for dam safety? It means that it is now easier to evaluate seismic risk, even in areas where performing a standard Vs30 survey is difficult. Geometrics’ Atom-3C is the ideal tool to measure H/V spectral ratios, collect data more quickly and more easily than is possible using other survey types. The single acquisition unit and 3-component geophone are a technologically advanced, yet an easier-to-use and less expensive way of collecting data.
Dr. Hayashi is presenting his paper in room 209A on April 18, 2023, at 5:15 pm. More information about the SSA Annual Meeting can be found here.