Location of Sinkhole Extension by Seismic Refraction Tomography and GPR Methods

In 2008 a stream flow created a sinkhole near Park City, Utah, creating an irregular-shaped depression in the alluvium about 22 m long, 10 m wide and 6 m deep. The entire discharge of a nearby creek flowed into the sinkhole increasing the size of the sinkhole. A total of 10 GPR and 4 seismic refraction profiles were conducted to find lateral and vertical extensions of this sinkhole. Interpretation of GPR profiles reveals the top of the sinkhole and its lateral extension. The exact shape of the sinkhole and its vertical extension is not clear on the GPR profiles because the high attenuation of the EM waves due to the high water saturation at the study area. However, the seismic refraction tomograms show the exact location of the sinkhole in the X and Z directions. Three anomalies with very low velocities are shown on the tomograms corresponding to the karst/cavernous formations, which are surrounded by low velocity zones corresponding to the highly saturated soils/rocks. It is concluded that near-surface karst and other anomolous feature can be revealed by refraction tomography.