Open Bedrock Cavity

Expected Geophysical Anomalies

Soil-Filled Bedrock Cavity

Expected Geophysical Anomalies

No Resistivity Anomaly
no wet soils, and air and rock have similar conductivity

No SP Anomaly
no moving water

No Seismic Refraction Anomaly
no rock depth variation

Probable Gravity Anomaly
open cavity is a mass deficiency

Imminent Sinkhole Hazard
Low

Probable Resistivity Anomaly
soil in cavity is a local conductivity high

No SP Anomaly
no moving water

No Seismic Refraction Anomaly
no rock depth variation

Subtle Gravity Anomaly
soil in cavity is a slight mass deficiency

Imminent Sinkhole Hazard
Very Low

Probable Resistivity Anomaly
due to wet/conductive soils

Probable SP Anomaly
moving water

No Seismic Refraction Anomaly
no rock depth variation

Probable Gravity Anomaly
open cavity is a mass deficiency

Imminent Sinkhole Hazard
High

Probable Resistivity Anomaly
soil in cavity and wet soil are both local conductivity highs

Probable SP Anomaly
moving water

No Seismic Refraction Anomaly
no rock depth variation

Subtle Gravity Anomaly
soil in cavity is a slight mass deficiency

Imminent Sinkhole Hazard
Low to Moderate

Subtle Resistivity Anomaly
locally thick soils

No SP Anomaly
no moving water

Seismic Refraction Anomaly
locally deep rock

Probable Gravity Anomaly
open cavity and locally deep rock are both mass deficiencies

Imminent Sinkhole Hazard
Moderate

Probable Resistivity Anomaly
soil in cavity and locally thick soils are both conductivity highs

No SP Anomaly
no moving water

Seismic Refraction Anomaly
locally deep rock

Probable Gravity Anomaly
soil in cavity and locally deep rock are both slight mass deficiencies

Imminent Sinkhole Hazard
Low

Probable Resistivity Anomaly
void in soil is a local conductivity low

No SP Anomaly
no moving water

Seismic Refraction Anomaly
void in soil is a local velocity low

Probable Gravity Anomaly
open cavity and soil void are both mass deficiencies

Imminent Sinkhole Hazard
High

Subtle Resistivity Anomaly
soil in cavity (conductivity high) and soil void (conductivity low) may partially cancel

No SP Anomaly
no moving water

Seismic Refraction Anomaly
void in soil is a local velocity low

Probable Gravity Anomaly
soil void and soil in bedrock cavity are both mass deficiencies

Imminent Sinkhole Hazard
High

Probable Resistivity Anomaly
void in soil is a local conductivity low

No SP Anomaly
no moving water

Seismic Refraction Anomaly
void in soil is a local velocity low

Probable Gravity Anomaly
open cavity and soil void are both mass deficiencies

Imminent Sinkhole Hazard
High

Subtle Resistivity Anomaly
soil in cavity (conductivity high) and soil void (conductivity low) may partially cancel

No SP Anomaly
no moving water

Seismic Refraction Anomaly
void in soil is a local velocity low

Probable Gravity Anomaly
soil void and soil in bedrock cavity are both mass deficiencies

Imminent Sinkhole Hazard
High

Probable Resistivity Anomaly
due to thick and wet/conductive soils

Probable SP Anomaly
moving water

Seismic Refraction Anomaly
locally deep rock

Probable Gravity Anomaly
locally deep rock and open cavity are both mass deficiencies

Imminent Sinkhole Hazard
Moderate to High

Probable Resistivity Anomaly
locally thick soil, soil in cavity and wet soil are all conductivity highs

Probable SP Anomaly
moving water

Seismic Refraction Anomaly
locally deep rock

Probable Gravity Anomaly
locally deep rock and soil in cavity ire both slight mass deficiencies

Imminent Sinkhole Hazard
Moderate

Possible Resistivity Anomaly
conductive thick and wet soils may partially cancel resistive soil void

Probable SP Anomaly
moving water

Seismic Refraction Anomaly
locally deep rock

Probable Gravity Anomaly
locally deep rock, bedrock cavity, and soil void are all mass deficiencies

Imminent Sinkhole Hazard
Very High

Possible Resistivity Anomaly
conductive locally thick soil, soil in cavity, and wet soil may partially cancel resistive soil void

Probable SP Anomaly
moving water

Seismic Refraction Anomaly
locally deep rock

Probable Gravity Anomaly
locally deep rock, soil in bedrock cavity, and soil void are all mass deficiencies

Imminent Sinkhole Hazard
High

Notes: These cartoons depict simple “end-member” cases. Other combinations of karst features are not only possible, but likely, in many karst terranes. These cases assume a residual clay soil. Different anomalies may be expected in karst areas with sandy soils (e.g. Florida). Although only seismic refraction is evaluated above, Enviroscan has successfully employed other seismic techniques (e.g. surface wave analysis, crosshole and/or uphole tomography, and reflection - particularly shear wave reflection) to detect and discriminate these and other combinations of karst features.