Amy Osborn
Multicomponent Seismic Tests in Yellowstone National Park

Amy L. Osborn and James B. Harris, Millsaps College, Jackson, MS 39210

With improvements in seismic acquisition instrumentation and methods of data analysis, multicomponent seismic methods have become increasingly more common in identifying the mechanical and hydrological characteristics of near-surface materials. A four-component (2X2 data matrix) shear wave (S-wave) seismic test was performed adjacent to Soda Butte Creek in the northeastern part of Yellowstone National Park. The purpose of this investigation was to evaluate data acquisition parameters for future seismic profiling in support of a hydrology/geomorphology/geochemistry study that is currently being undertaken by students in the Department of Geology. Analysis of S-wave seismic refraction data indicates a high velocity layer at an approximate depth of 13 m (possibly related to glacial material that fills the valley). A time delay between the principal components (XX and YY) of the data matrix for the refracted arrival indicates the possibility of an azimuthally anisotropy near surface. There is also evidence of an S-wave reflection from this boundary. In addition, significant conversion of S-wave to P-wave (compressional) energy has been identified and modeled. Detailed analysis of this data set, and a similar multicomponent seismic test near the Soda Butte hydrothermal feature, will provide a more complete geophysical understanding of the Soda Butte Creek alluvial valley and allow us to choose appropriate acquisition and processing parameters for future seismic investigations in the area.