VS30Characterization of Texas, Oklahoma, and Kansas Using the P-Wave Seismogram Method

The P-wave seismogram method is used to develop estimates of the time averaged shear wave velocity of the upper 30 m (VS30) at 251 seismic stations in Texas, Oklahoma, and Kansas. Geologic conditions at the sites are documented using large-scale geologic maps. The VS30values from the P-wave seismogram method agree well with the limited in situ measurements across the study area and correlate well with the mapped geologic units. Compared with the VS30proxy values assigned to the stations by the Next Generation Attenuation–East (NGA-East) project, the P-wave seismogram method generally produces larger VS30estimates. These differences are likely due to the fact that very few VSmeasurements in Texas, Oklahoma, and Kansas were available for use in the development of the NGA-East proxies. Analysis of the P-wave seismogram VS30values indicates that, in this geographic area, incorporating rock type along with geologic age better distinguishes the average VS30of these materials than geologic age alone.