RAYLEIGH-WAVES IN QUATERNARY ALLUVIUM FROM EXPLOSIVE SOURCES - DETERMINATION OF SHEAR-WAVE VELOCITY AND Q-STRUCTURE

We deployed a Linear array aligned with the shot point on the river sediments. Sixteen digital, three-component recording stations were used; the minimum distance from the source was 1.9 km, and we chose an interstation separation of 50 m, for a total array length of 750 m. Clear Rayleigh waves were recorded along the array, and we were able to recognize two propagating modes in the waveforms. We calculated the dispersion curves of group velocities using a multiple filter technique. Dispersion curves of phase velocities were calculated using a p-omega stacking technique.

Surface-wave propagation in unconsolidated Quaternary alluvium has been investigated within the valley of the Chiusi Lake tributary (Central Italy). The seismic experiment was originally designed to determine the structural response of an Etruscan tomb to a 200-kg dynamite shot, planned as part of a refraction survey within the CROP-DSS (an Italian project for the investigation of deep crustal structures). The availability of many recording instruments allowed us to design a more complete experiment, and we decided to use surface waves generated by a small explosion (10 kg dynamite) to infer the shear-wave-velocity-attenuation model in the alluvium layer.