Surface Seismic Methods for Locating and Tracing Earth Fissures and other Significant Discontinuities in Cemented Unsaturated Soils and Earthen Structures

Seismic refraction methods have been used for more than a decade to locate earth fissures and other significant discontinuities in unsaturated, cemented soils that present potential risks to various facilities. Recently, these methods have been adapted to locating areas of potential significant cracking within earthen structures, including large flood control embankments. Earth fissures and connected cracks in normally dry embankments have potential under flood induced erosion to cause failures in such structures or at linear infrastructure such as roads and canals. The essence of these methods is to identify anomalous large signal attenuations and (or) first arrival time delays in standard multi-channel seismic refraction data. Locations of anomalous attenuation or time delays are interpreted in the field and marked on the ground. Using a series of profiles along an earth fissure or other discontinuity trace, actual positions of the features can be determined. Once the locations of such features have been determined, further geologic investigation, including test pits, are typically used to verify and assess the features and potential hazard. These methods have been used to locate and trace earth fissures in Arizona and Nevada, including in urbanized areas of Las Vegas and at industrial ponds and flood control dams.