From the study of the speed of seismic waves (P, S, Rayleight) it will be possible to define the properties of the ground under study and, depending on the specific case, refraction seismic, reflection seismic, seismic tomography, downhole, crosshole, MAM / MASW seismic and measurement of vibrations or seismic noise, will offer greater precision or information to achieve the desired objective.
Refraction, Reflection, Seismic Tomography
Seismic prospecting is mainly based on the study of the speed of P and S waves, from which to define the characteristics of the geological formations under study. The value of Vp and Vs will indicate their status, geological contacts, fault zones or fractures, as well as excavatable, ripable, threshold or non-ripable levels.
Surface Wave Measurement (MAM / MASW)
The multichannel analysis of Surface Waves is a geophysical method that basically consists of estimating the values of the shear velocity (Vs) along the ground by means of the spectral analysis of the environmental seismic noise or, by means of the deformation generated by the impact of an active source (hammer, mallet, weight drop, etc.). It is a technique that is currently being used regularly for the geotechnical characterization of the terrain in those areas with a high level of environmental noise, such as urban environments, proximity to highways, airports, railways, etc., as well as in areas in those that existing a low noise level, it is possible to generate surface waves by hitting.
The objective of reconnaissance by downhole or crosshole seismic is to determine the dynamic modulus of deformation (Young, Stiffness and Compressibility) and Poisson's index, from the velocity values Vp and Vs of the materials traversed by a borehole. To do this, it is necessary to generate a compressional wave train (P waves) and a shear wave train (S waves) by means of a suitable source (usually a mallet, well hammer, airgun or sparker), recording the wave train generated with a triaxial borehole geophone or an hydrophones/geophones streamer.
Seismic Site Analysis (HVSR)
The horizontal-vertical spectral ratio (HVSR) technique is a passive seismic method used to determine the resonance characteristics of a site. Using environmental micro-earthquakes recorded with a 3-component geophone / accelerometer, the fundamental ground resonance frequency can be obtained.
In earthquake engineering, HVSR data is important for understanding site effects. It was developed in the 1980s by Yutaka Nakamura and is also known as the Nakamura method.