In-situ measurements of seismic velocity at 27 locations in the Los Angeles, California region

Studies conducted in the San Francisco Bay Region (Gibbs, Fumal and Borcherdt, 1980) have shown that average shear-wave velocity can be readily tied to quantitative estimates of ground motion such as ground amplification and earthquake intensity. Furthermore, when certain physical properties of the geologic materials such as texture, hardness and fracture spacing are observed during geologic mapping, a method can be used to predict shear-wave velocity from the descriptions of geologic units. By measuring shear-wave velocities in key units together with the above data, regional maps depicting the earthquake shaking hazard can be compiled. The goals of the current program are to provide shear-wave data in the Los Angeles area to compare with that in the San Francisco Bay Region where high-strain intensity data are available. Data from twenty-seven locations are summarized in this report as part of a continuing project to seismically zone the Los Angeles area.