V S 30 Characterization 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 ( V S30 ) at 251 seismic stations in Texas, Oklahoma, and Kansas. Geologic conditions at the sites are documented using large-scale geologic maps. The V S30 values 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 V S30 proxy values assigned to the stations by the Next Generation Attenuation–East (NGA-East) project, the P-wave seismogram method generally produces larger V S30 estimates. These differences are likely due to the fact that very few V S measurements in Texas, Oklahoma, and Kansas were available for use in the development of the NGA-East proxies. Analysis of the P-wave seismogram V S30 values indicates that, in this geographic area, incorporating rock type along with geologic age better distinguishes the average V S30 of these materials than geologic age alone.