New Zealand Community Fault Model – version 1.0.

Abstract

Fault models developed by the scientific community aim to provide a consistent and broadly agreed-upon representation of faults in a region for such societally important endeavours as seismic hazard assessment (e.g. national seismic hazard models), strong ground-motion predictions and physics-based fault systems modelling. The New Zealand Community Fault Model (NZ CFM) is a two- and three-dimensional representation of fault zones associated with the New Zealand plate boundary for which Quaternary activity has been established (or deemed probable) and are, in the main, considered capable of producing moderate- to large-magnitude earthquakes. The NZ CFM builds on the Active Fault Model of New Zealand (Litchfield et al. 2013, 2014), updates that model through science community engagement and input and extends the updated faults from the surface to seismogenic depths. A nominal compilation scale of 1:500,000– 1:1,000,000 was chosen to provide representative surface fault traces consistent with finer-scale representations, such as the New Zealand Active Faults Database. Faults in the model are defined based on criteria that include surface geology, seismicity, seismic reflection profiles, bores and geologic cross-sections. The first edition of the NZ CFM (v1.0) is populated from 36.0 to 49.8° S and from 163.5° E to 179.0° W and comprises two principal datasets. The first dataset is a two-dimensional (2D) map representation of active (or potentially active) fault zone traces. This 2D fault zone representation contains information on the geometric and kinematic attributes of each fault zone or fault zone segment as expressed on the ground surface. Generalised estimates of geometric (dip and dip direction), kinematic (sense of movement, rake and net slip rate) and slip rate timeframe parameters have been provided for most fault zones, along with assigned uncertainties. In addition, a ‘Quality Code’ provides an indication of the quantity and type of data available for each fault zone, weighted toward the quality of the slip-rate data. The second dataset is a three-dimensional (3D) triangulated mesh surface representation of the fault zones in the model. However, there are some important differences between the 2D and 3D fault zone models; in particular, major fault zone intersections and subduction plate interfaces. NZ CFM v1.0 is publicly available from the GNS website. The NZ CFM v1.0 data package includes ArcGIS and QGIS projects and shapefiles of the 2D fault zone model, a MOVE project and triangulated surfaces for the 3D fault zone model, tabulated fault zone parameters and documentation.