f Impact shear wave generator for dynamic shallow soil characterisation

P and S waves are used to determine Poisson ratios that are useful for micro zoning in seismic engineering studies. P waves are easily generated by many vertical impact sources. On the other hand S waves are commonly obtained by a polarised sideways impact on a heavy beam perpendicular to the line of geophones (MOONEY, 1973). Any S wave source always produces some P wave component that can be extracted from the paired field data. Each pair consists of two opposite polarity records generated by inverted directional impacts. Recently developed sources are based on a vibration sweep pulse (GHOSE et al, 1996) requiring dedicated hardware and processing software and thus making it impossible to use with standard engineering seismographs.