Seismic

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Seismic techniques are commonly used to determine site geology, stratigraphy, vibration studies, bedrock delineation, and rock quality. These techniques provide detailed information about subsurface layering and subsurface mechanical properties using seismic waves. Reflection and refraction methods are historically the most commonly used seismic techniques, whereas MASW profiling is a relatively new approach in obtaining shear wave profiles. Reflection and refraction methods determine geological structure and rock velocities by either refracting or reflecting waves off boundaries between soil and/or rock units with different seismic velocities. MASW measures the seismic surface waves generated from either an active source (i.e. sledge hammer), passive source, or both.

To greatly improve field efficiency, Gehrig, Inc. designed and built a land streamer, which is an array of geophones designed to be towed along the surface. Not only does the land streamer enable seismic exploration methods to become more economically feasible without significantly affecting data quality, it provides additional flexibility in performing seismic exploration techniques over hard surfaces such as asphalt and concrete pavements, roads, and/or foundations without having to drill. Data collection via a land streamer is most beneficial for MASW profiling.