High-resolution seismic imaging of mine-related hazards along Illinois route 29 north of Peoria, Illinois

Geophysists run seismic lines along I29

Abstract- We acquired 15 km of seismic reflection and refraction profiles along a highway in central Illinois to locate old subsurface mine workings that may indicate areas of potential instability. Illinois Route 29, a major highway along the western side of the Illinois River Valley, swings close to steep bedrock bluffs for several miles in northern Peoria and southern Marshall Counties. Coal seams that crop out along these bluffs have been intensively mined and two mines, both now abandoned, were known to work deposits beneath the level of the valley floor. The seismic investigation was part of a detailed geologic study of the highway corridor in preparation for a major renovation project.

The 48-channel data set was collected using a 100-lb accelerated weight drop source with a 20-ft source spacing and 10-ft receiver spacing. We applied standard reflection processing and a simple 2-layer velocity model for refraction analysis. Disruptions in the bedrock reflections at the depth of the mines were imaged at several locations. Refraction analysis indicated irregularities on the bedrock surface that may be caused by collapse or landslide. Integrating the two seismic techniques provides greater insight into the subsurface than either employed separately.

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