The Cape Egmont Fault Zone in the southern Taranaki Basin, New Zealand, is a complex series of synthetic and antithetic dip-slip normal faults accommodating present-day extension. The fault zone comprises new and reactivated faults developed over multiple phases of plate boundary deformation during the last 100 Myrs. The fault zone is well imaged on petroleum industry seismic reflection data, with a number of faults exposed and studied onshore. The Cape Egmont Fault Zone is seismically active, with damaging historic earthquakes of up to Mw 5.4. Most earthquakes occur beneath the Late Cretaceous to Holocene sedimentary sequence at depths greater than 5–8 km. The maximum depth of fault rupture is c. 20 km, above which 90% of recorded earthquakes occur. Focal mechanisms from these earthquakes generally indicate strike-slip to oblique-normal faulting, which contrasts with the predominantly dip-slip faulting observed in the overlying sedimentary sequence and surface fault traces. Data from regional earthquake studies and petroleum well deformation show faults imaged in the sedimentary sequence to be preferentially oriented for slip in the present-day stress field. The greatest earthquake risk is on major basement-penetrating crustal-scale faults greater than 20 km in length. Fault lengths and maximum vertical offsets of the sedimentary sequence, determined from a three-dimensional structural model, are consistent with global displacement-length scaling relationships. This validation permits fault lengths to be used to determine potential future earthquake magnitudes using global fault length-magnitude relationships. Fault lengths of post-Pliocene normal faults are typically ≤21 km, resulting in maximum predicted magnitudes Mw 6.3. The most likely earthquake magnitude from the fault population sampled is Mw 5.4 ± 0.5. The largest and most mature fault – the Cape Egmont Fault – is at least 53 km long and, depending on the number of segments ruptured during a future event, is capable of generating an earthquake between Mw 7 and 7.3. New sub-surface radiometric ages constraining the age of the ring plain created by Taranaki Maunga and its predecessors support 3 Myrs of continuous volcanism in the region. Hornblende from 14 igneous samples from onshore petroleum exploration wells have yielded 40Ar/39Ar plateau ages ranging from c. 2.9 Ma to 0.15 Ma. Seven 40Ar/39Ar samples from near the base of the Taranaki Maunga ring plain (previously dated at <0.2 Ma) ranged from 0.515 Ma in the Kapuni-15 well on the south side of Taranaki to 0.39 Ma in Rahotu-1 on the western side. These data suggest that surficial volcanism, including Taranaki Maunga, initiated between 0.5 to 0.4 Ma. DOI: https://doi.org/10.21420/ED9K-EP20 Cite data as: Seebeck H, Thrasher GP, Viskovic GPD, Macklin C, Bull S, Wang X, Nicol A, Holden C, Kaneko Y, Mouslopoulou V, Begg JG. 2021. Geologic, earthquake and tsunami modelling of the active Cape Egmont Fault Zone. Lower Hutt (NZ): GNS Science. 370 p. (GNS Science report; 2021/06). doi:10.21420/100K-VW73. (with data available at DOI: https://doi.org/10.21420/ED9K-EP20) Thrasher GP, Viskovic GPD, Sagar M, Seebeck H. 2024. Subsurface igneous rocks of the Taranaki Peninsula. Lower Hutt (NZ): GNS Science. 77 p. (GNS Science report; 2023/47). https://doi.org/10.21420/8BEH-6P24. (with data available at DOI: https://doi.org/10.21420/ED9K-EP20)

This originates from various sources including: New Zealand Petroleum & Minerals' New Zealand Petroleum Basins Publication 2010 (transects created by C.I. Uruski of GNS Science). K.J. Bland & D.P. Strogen 2012 Regional seismic transects of selected lines from Taranaki Basin, GNS Data Series 7a. K.J. Bland 2012 Regional seismic transects of selected lines from East Coast Basin, GNS Data Series 7b. K.J. Bland, B.D. Field, A.G. Griffin, D.W. Heron, M.J. Isaac, Z. Juniper, C.I Uruski 2012 Play-based Assessment of the Pegasus and East Coast Basins, GNS Science Data Series Report 9b. 4D Taranaki Mapping project - unreleased. Other previously published GNS scientific papers.

This dataset contains geospatial datasets for sedimentary basins in the Northwest Province (Taranaki, Deepwater Taranaki, and Reinga-Northland basins), produced and compiled as part of GNS Science's "Atlas of Petroleum Prospectivity" programme (APP). APP is synthesising the wealth of new and existing information and knowledge within GNS Science and other open-file sources, to produce a nationally-significant baseline reference dataset that summarises the current understanding of the petroleum prospectivity of New Zealand's offshore sedimentary basins. Polygon, point, and polyline features are organised thematically into Feature Datasets, each of which contains multiple Feature Classes. Raster datasets are included at the highest hierarchical level of the database. The co-ordinate system used for the database is New Zealand Transverse Mercator, based on the NZGD2000 datum. Database compilation was undertaken using ArcGIS 10.3.1 for Desktop (version 10.3.1.4959). For further information on these data, please refer to: Arnot, M.J. and Bland, K.J. et al. (Compilers), 2016. Atlas of Petroleum Prospectivity, Northwest Province: ArcGIS geodatabase and technical report. GNS Science Data Series 23b.