An Earthquake Simulator for New Zealand

Bruce E. Shaw, Bill Fry, Andrew Nicol, Andrew Howell, & Matthew C. Gerstenberger

Published February 1, 2022, SCEC Contribution #11836

We present an earthquake simulator for New Zealand. It uses the Rate‐and‐State Earthquake Simulator engine based on approximations of the rate‐and‐state friction equations. The full set of faults considered in the most recent New Zealand national seismic hazard maps are included in the simulator. New simulator methods are introduced that allow for the inclusion and interaction between upper plate faults and a subduction interface fault below them. The simulator generates sequences of complex slip events and a catalog of finite ruptures hundreds of thousands of years in length. Results from the simulator are evaluated through statistical testing and comparison with geological and geophysical observations. These evaluations include a spatial comparison against historical earthquakes, a comparison against rates of events in the instrumental catalog, and a comparison against scaling relations. Consistency of the model with these measures is generally found, though some differences with productivity is noted, due to incomplete modeling of subducting slab features like geodetically inferred spatially dependent creep and dense faulting in Bay of Plenty faults. Significant emergent aspects of the resulting synthetic catalog are discussed. These include substantial variability over instrumental catalog timescales, clustering of large events in space and time, and spontaneous ruptures that break both the upper crustal faults and subduction interface coseismically. An online repository provides the model output, and an additional site provides python code for reproducing some of the figures in this article and tools for further model output analysis.

Shaw, B. E., Fry, B., Nicol, A., Howell, A., & Gerstenberger, M. C. (2022). An Earthquake Simulator for New Zealand. Bulletin of the Seismological Society of America, 112(2), 763-778. doi: 10.1785/0120210087.