New Zealand Journal of Geology & Geophysics abstracts

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Effects of attenuation in the Taupo Volcanic Zone on patterns of spatial distribution of ground shaking in New Zealand earthquakes

David Dowrick

21 Kotare Crescent
Tauranga 3112, New Zealand

Abstract    The attenuation of earthquake waves is higher in the Taupo Volcanic Zone (TVZ) than in the crust of the rest of New Zealand. This causes characteristic modifications to the patterns of spatial distribution of ground shaking in and around the TVZ, as shown by Modified Mercalli intensities, in 55 earthquakes of M_w 5.0–7.8, supported by previous studies of peak ground and spectral accelerations over a wide range of frequencies and amplitudes. These effects are explained by simple comparisons of the attenuation of seismic waves travelling along TVZ and non-TVZ paths. Three different characteristic patterns of isoseismals arise depending where earthquakes are located in relation to the TVZ. Seismic hazard modelling of the effects of the TVZ is more complex than previously thought; for example, for deep earthquakes (≥70 km), 3D modelling of not only the crust but also the subducting Pacific plate and the mantle is required.

Keywords    attenuation; isoseismals; Taupo Volcanic Zone; peak ground accelerations; spatial distribution of ground shaking

G07004; Online publication date 21 September 2007; Received 14 March 2007; accepted 21 August 2007

New Zealand Journal of Geology & Geophysics, 2007, Vol. 50: 315–325
0028–8306/07/5004–0315  © The Royal Society of New Zealand 2007

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