Anisotropy in strong ground motion in the 1994 Arthur's Pass earthquake
Thesis DisciplineCivil Engineering
Degree GrantorUniversity of Canterbury
Degree NameMaster of Engineering
Directivity effects are assessed by examining strong ground motion records from the 1994 Arthur's Pass earthquake in light of evidence presented by past researchers. This thesis focusses primarily on intra site differences in anisotropic ground motion, achieved by analysing different components of ground motion. Problems are encountered in the selection of a fault plane. It is most likely that the fault plane assumed for analysis is not consistent with the actual fault plane. Despite these problems, some observations of anisotropic behaviour are made at the Arthur's Pass, Flock Hill and Lake Coleridge sites that are consistent with rupture on the assumed fault plane. The determination of directivity effects is based on analysis of fault normal and fault parallel components of acceleration, velocity and displacement records, in addition to Fourier and response spectra derived from the ground motion acceleration records. A further study is carried out on peak ground accelerations. Existing directivity research deals primarily with fault normal amplification in forward rupture directivity regions; that is, at sites located in the path of the moving rupture front. The results of a simple model application suggest that in some cases, fault parallel amplification may be significant next to fault planes. This is highlighted in far field Fourier amplitude predictions for the Arthur's Pass Police Station.