Auckland Faults QGIS database, GIS file for Appendix 1

Abstract

Locating faults can be challenging in urban environments and low-strain rate regions, where anthropogenic and surface processes between earthquakes erode surface expressions of faulting. Concealed fault detection is critical for hazard assessment and mitigation, as earthquakes on unidentified faults can have serious consequences. Common geophysical methods for identifying subsurface faults are challenging to implement in urban areas due to, for example, difficulties associated with permitting and anthropogenic noise. However, urban development can provide rich resources for identifying concealed faults, such as geotechnical boreholes and high-resolution LiDAR topography. The Tāmaki Makaurau Auckland area of Aotearoa/New Zealand is the country’s most populated region in a relatively tectonically stable setting, where intense urbanisation and Quaternary volcanics mask potential faults. We developed a new methodology and workflow to identify and assess the reliability of concealed structures in Auckland, using borehole, geophysical and outcrop data. From a database of >8,200 boreholes, we identify 46 post-Miocene structures, including ten likely and 25 possible faults. We also provide a new QGIS database of borehole and fault data to enable future refinement of our interpretations. This work shows how data associated with urbanisation can be leveraged to complement traditional methods of identifying concealed faults.