Development of deep Vs profiles and site periods for the Canterbury region


Recent field investigations were carried out to define the shear wave velocity ( V S ) profile and site periods across the Canterbury region , supplementing earlier efforts in urban Christchurch . Active source surface wave t esting , ambient wave field (passive) and H/V spectral ratio methods were used to characterise the soil profile in the region. H/V spectral ratio peaks indicate site periods in the range of 5 -7 seconds across much of the Canterbury Plains, broadly consisten t with those based on a 1D velocity model for the region. Site periods decrease rapidly in the vicinity of the Canterbury foothills and the Banks Peninsula outcrops. In Christchurch, the Riccarton Gravels result in a significant mode of vibration that has a much shorter period than the site period of the entire soil column down to basement rock.

New Zealand Society for Earthquake Engineering Conference