The HVSR technique arose from observations made in Japan at strong-motion stations in the national network. It was noted that stations on soft ground experienced a significant change in horizontal components compared to stations located on very "hard" ground, or on bedrock.

In 1983, Nakamura demonstrated how the analyzed peak in an HVSR curve is strongly related to soil characteristics. He highlighted how this change in the horizontal plane is not entirely due to Rayleigh waves alone, but also to the SH component of S waves generated by the refraction of P waves at the bedrock/soil interface and at interfaces within the soil stratigraphy itself.

HVSR technique diagram - On the H/V spectrum - Yutaka Nakamura - 2008

The amplitude value of the H/V ratio allows to evaluate the ground amplification factor for SH waves, while double the value of the peak frequency allows to evaluate the effect of Rayleigh waves and/or multiple reflections of SH waves (Nakamura - 2008).

Thanks to our GeoBoxtool, in the various possible configurations, and our GeoExplorer software, it is possible to record, analyze and model the stratigraphic profile.