Abstract
Beneath Hawke's Bay, the interface between the subducted Pacific and overlying Australian plates lies at shallow depth - within the depth range where large subduction thrust earthquakes are expected. Determining the likely size of such earthquakes is thus a major issue in quantifying the seismic hazard of the region. Here we use recent seismological, geodetic and geologic research results to estimate the rupture dimensions, magnitude and recurrence of a large subduction thrust event. The estimated rupture zone extends 45 km downdip, from 15 km to 22 km depth on the plate interface, and 120 km along strike, from 45 km southwest of Napier to 10 km northeast of Wairoa. This equates to an Mw 7.7 earthquake. The estimated recurrence of such an event depends on the coupling coefficient (i.e. the ratio of seismic slip to total slip) at the plate interface, which is not well determined. Our preferred range for this coefficient is 0.3-0.5, which yields a recurrence interval range of 250-400 years. Such recurrence is broadly consistent with the geological record of subsidence in the Ahuriri Lagoon near Napier in the 3500 years prior to the Ms 7.8 Hawke's Bay earthquake of 1931.
Highlights
In the Hawke's Bay region, the Pacific and Australian plate are converging obliquely at about 42 mm/yr (DeMets et al, 1994: Fig. I). This relative motion is accommodated by subduction of the Pacific plate and deformation of the overlying Australian plate
The subducted plate dips to the northwest, and in the Napier/Hastings region the plate interface is about 20 km deep (Ansell and Bannister, 1996)
The potential for a large thrust earthquake at the plate interface is a major issue in quantifying the seismic hazard in Hawke's Bay
Summary
Beneath Hawke's Bay, the interface between the subducted Pacific and overlying Australian plates lies at shallow depth - within the depth range where large subduction thrust earthquakes are expected. The estimated rupture zone extends 45 km downdip, from I5 km to 22 km depth on the plate interface, and 120 km along strike, from 45 km south west of Napier to 10 km northeast of Wairoa. Our preferred range for this coefficient is 0.3-0.5, which yields a recurrence interval range of 250-400 years Such recurrence is broadly consistent with the geological record of subsidence in the Ahuriri Lagoon near Napier in the 3500 years prior to the M., 7.8 Hawke's Bay earthquake of 1931
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Bulletin of the New Zealand Society for Earthquake Engineering
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
