Impact of variable fault geometries and slip rates on earthquake catalogues from physics-based simulators for the Cape Egmont Fault, New Zealand.

Abstract

Physics-based earthquake simulators have been developed to overcome the relatively short duration and incompleteness of historical earthquake and paleoseismic records. Earthquake simulators produce millions of synthetic earthquakes over thousands to millions of years using predefined fault geometries, locations and slip rates. Due to the sparsity of geological and/or geodetic data combined with limited computing-power capabilities, it is common to simplify input parameters for earthquake simulators.

This study uses an exceptionally well-defined 3D geometry of an active normal fault in offshore New Zealand, the Cape Egmont Fault, to demonstrate the impact of using non-uniform slip rates and realistic fault geometries on the resulting synthetic earthquakes. Adopting variable slip rates reduces unexpectedly high nucleation rates of seismicity along the fault edges and unrealistic distributions of events with increasing depth. Introduction of complex 3D fault geometries, including fault segmentation and bends, produces less characteristic earthquake populations.