Tectonic history of the Waimea-Flaxmore Fault System (W-FFS) from the Nelson-Richmond urban area to D’Urville Island is analysed through six regional transects that join offshore, depth-converted seismic lines in Tasman Bay to onshore cross sections. Accrual of reverse separation on the W-FFS since c. 19 Ma is recorded by folding of the Neogene cover sequence, associated with fault propagation during reactivation of inherited normal faults. Coeval inception of movement on the F-WFS along its entire length contrasts with the subsequent evolution, with persistent Plio-Quaternary activity in onshore Nelson versus cessation of activity along the eastern margin of Tasman Bay since c.7 Ma. From north of Nelson (Cape Soucis) to D’Urville Island the western faults of the W-FFS are buried below Plio-Quaternary marine sediments and the up-thrust panels are segmented by the newly identified, c. E-W, Croisilles Fault Zone, Cross Point and D’Urville faults, with cumulative dextral offset of c. 27 km from Cape Soucis to D’Urville Island. The c. E-W faults extend from the onshore into Tasman Bay and are interpreted as the northernmost Late Miocene strands of the Marlborough Fault System that have accommodated incipient distributed shear in the crustal block north of the Queen Charlotte Fault Zone. Segmentation and along-strike changes of the W-FFS occur at the transition from the Nelson contractional domain to the northern Marlborough strike-slip domain, driven by large-scale kinematics of the Pacific-Australia plate boundary. Inactivity of the eastern Tasman Bay strands of the W-FFS since 7 Ma suggests that risk of rupture and related tsunami generation are significantly lower relative to the southern onshore segments that have ruptured in the last 20 ka. However, given the incompleteness of offshore data and the short record of historical seismicity we cannot rule out the possibility that faults in eastern Tasman Bay can be reactivated in the present-day tectonic regime.Supplemental File 1 (with Figure S1-1) provides a detailed description of the W-FFS in onshore Nelson.Supplemental File 2 shows the geological transects T1-T6 (Figures 8-13 in the paper), reproduced at the same scale in large format, to facilitate evaluation of the proposed geological interpretation.Supplemental File 3 (with Figure S3-1) discusses the role of mechanical weakness and fluid overpressure on reactivation of the W-FFS.
These Supplemental Files accompany the paper submitted for pub...