Seismic hazard classifications and Vs30 in Connecticut using MASW and HVSR methods

Five new seismic hazard classifications for Hartford County, Connecticut (CT), were proposed by New England State Geologists (NESG) in an effort to improve the current USGS Seismic Hazard Map. These classes were derived from mapped surficial materials, but in situ information is required to verify this approach. Therefore, active and passive surface wave techniques were performed at thirty field sites to determine V_S30 and compare the results to the NESG map. Passive data were processed using the Horizontal-to-Vertical Spectral Ratio (HVSR); active data were processed with the multi-channel analysis of surface waves (MASW) technique. The field investigation demonstrated that the surficial material-based system was not sufficient for 66% of the field sites and in-situ velocity information from at least two methods should be considered for improved classification. The geophysical work discussed here represents the first field de-rived V_S30 values for Hartford County, CT.