Using Shear-wave Velocity to Detect Void-induced Changes in Stress

Shear-wave velocity is directly related to stress; therefore, changes in stress may result in observable shear-wave velocity variations detectable using surface seismic methods. Shear-wave reflection and surface wave data were analyzed from multiple sites containing subsurface voids. Changes in shear-wave reflection velocity correlate to known subsurface conditions, including increased velocity over unstable voids with potential for roof collapse and decreased velocity over voids that have already experienced failure, forming sinkholes at the surface. Shear-wave velocity profiles inverted from surface wave data also show low-velocity anomalies with overlying high-velocity closures indicative of a subsurface void and associated increased stress on the supporting walls and roof rock. Shear-wave velocity may serve as an indicator of void presence and increased failure potential associated with stress build up, which may aid in public safety and remediation efforts in void-prone areas.