New Zealand Fault-Rupture Depth Model v1.0: a provisional estimate of the maximum depth of seismic rupture on New Zealand’s active faults

This report and associated data presents a new and provisional estimate of the maximum depth of rupture on New Zealand’s active faults (“New Zealand Fault-Rupture Depth Model v1.0”) based on a combination of two independent models. The first model uses regional seismicity distribution from a relocated earthquake catalogue to calculate the 90% seismicity cut-off depth (D90) representing the seismogenic depth limit H. This is multiplied by an overshoot factor representing dynamic propagation of rupture into the conditional stability zone and accounting for the difference between regional seismicity depths and frictional properties of a mature fault zone, to arrive at rupture depth Df. The second model uses surface heat-flow and rock type to compute thermal stability limits for seismogenic faults. These limits are also multiplied by an overshoot factor to arrive at a thermally-based maximum rupture depth Df. Both models have depth cut-offs at the Moho and/or subducting slabs. Results indicate maximum rupture depths between 8 km (Taupō Volcanic Zone) to > 30 km (e.g. southwest North Island), strongly correlated with regional thermal gradients. Preliminary estimates of uncertainties for each model are also discussed. Depths from the two models show broad agreement for most of the North Island and some differences in the South Island. A combined model using weighting based on relative uncertainties is derived and validated using constraints from hypocentre and slip model depths from recent well-instrumented earthquakes. (auth) DOI: https://doi.org/10.21420/0BBW-V059 Cite data as: Ellis SM, Bannister S, Van Dissen RJ, Eberhart-Phillips D, Holden C, Boulton C, Reyners ME, Funnell RH, Mortimer N, Upton P. 2021. New Zealand Fault Rupture Depth Model v1.0: a provisional estimate of the maximum depth of seismic rupture on New Zealand’s active faults. Lower Hutt (NZ): GNS Science. 47 p. (GNS Science report; 2021/08). doi:10.21420/4Q75-HZ73. (with data set available at DOI: https://doi.org/10.21420/0BBW-V059)