Passive near-surface seismic data where all else fails

Geotechnical engineers remain busy assessing and rebuilding U.S. infrastructure, as part of the American Recovery and Reinvestment Act (ARRA) of 2009. Opportunities abound in the reconstruction of bridges and interstate highways, and also in the construction of mass transit systems. Acquiring useful shallow (< 200 ft) seismic data in noisy urban conditions has always been difficult. The site conditions beneath bridges or in high-volume traffic corridors generally preclude acquisition of quality seismic data. Acquisition adjustments historically have not been practical, and the results were seldom useful to the project engineer. But just because these sites are located in difficult urban settings does not mean geophysical imaging should be overlooked as a source of valuable information for engineering design or construction. With the advent of surface wavefield methods, particularly passive surface-wave recording, urban site conditions no longer pose the same limitations to all surface-based geophysics.