Which Geophysical Method?
Electrical Resistivity Imaging (ERI) can be use to map project area that have potential for subsurface problems. This technique could provide 2D or 3D spatial models of subsurface depends on the field acquisition and client requirement. Complex subsurface features especially at limestone area can be mapped using this technique.
Seismic Refraction also a suitable geophysical technique in providing cross-sectional depth information at limestone or karstic areas.
Seismic Reflection method is another option in delineating subsurface features. Seismic reflection survey widely used in mapping subsurface structures and stratigraphy.
How These Geophysical Techniques Could Help?
Electrical resistivity imaging (E.R.I) or resistivity survey can profile the subsurface by separating the overburden and limestone bedrock. Generally, the bedrock will have higher resistivity values compared to the overburden. Similar to cavity or void which are present as anomalies in the resistivity result. Either they are having resistivity values or low resistivity values compared to the background values.
Seismic refraction also can be used in subsurface analysis. Basically, the mud-filled cavity or water-filled cavity has a velocity contrast with the surrounding rock or bedrock. Therefore, seismic refraction tomography is one of the effective tools for mapping this feature.
In seismic reflection survey, subsurface features can be interpreted from the stacked seismic section. The interpretations are made based on the reflection geometry, amplitude, frequency and interval velocity.