Reflection and refraction seismics

Applications:

  • Detection of tectonically caused fault zones, displacements, veins
  • Thickness determination of overburden and overlying strata
  • Detection of joints
  • Examination of hydrogeological and geological engineering issues (aquifers, stability)
  • Discrimination of unconsolidated rock / solid rock
  • Exploration of dolines

Principle of measurement:

Principle of measurement using reflection seismics
Principle of measurement using refraction seismics

Seismic sources:

Seismic source: EWG III
Seismic source: sledge hammer
Seismic source: vibration equipment

Examples:

Seismic exploration in a salt mine into the overburden (reflection seismics)
Exploration on sink holes on a building site (refraction seismics)

Seismic tomography

Seismic tomography can for example be done between two bore holes and it analyses the running time of seismic waves, which have passed through the object in question on a straight path, directly. Seismic tomography is generally carried out between two bore holes, two adjacent drifts or an underground drift and the ground level. One side is used for the source and the other one for the receiver. The outcome shows the distribution of seismic wave speed in the section between source and receiver locations. High density areas result in high speeds, cavities show low speeds (sound through air) in the final plot.

Principle of measurement:

Principle of measurement of seismic tomography

Example:

Exploration on sink holes on a building site
One further example of the results of a K-UTEC campaign

Surface wave seismics

Principle of measurement:

When seismic energy is exited on the earth's surface high amplitude surface waves, whose energy is pincipally tied to the earth's surface, are generated beside body waves (pressure waves and shear waves). The most important property of surface waves is dispersion - this means that the velocity of wave propagation is dependent on the frequency of the oscillation. Surface waves exhibit comparably low wave lengths, which results in good chances for a high lateral resolution of surface near structures (up to about 10 m depth). Examples are the localisation and lateral outlining of contaminated sites, discovering of surface near anomalies (e.g. cavities, boulders, etc.). Beside velocity, surface wave seismics also uses and displays the scattering amplitude of the surface waves, which makes the position accurate exploration of surface near faults possible.