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Using a Multi-Cycle, Physics-Based Earthquake Simulator to Explore Rupture Connectivity for Seismic Hazard: The Aotearoa New Zealand Example

Description: 

Recent earthquakes demonstrate how complex earthquake rupture processes can be: examples include the multi-fault 2016 M7.8 Kaikōura (Aotearoa New Zealand) and 2019 M7.1 Ridgecrest earthquakes and the 2023 Kahramanmaraş earthquake sequence (Türkiye). It is important to account for the possible future occurrence of multi-fault earthquakes and sequences in seismic and tsunami hazard models. However, this is often challenging due to uncertainties on the timing of paleoearthquakes and the short duration of the historical record. To date, efforts to incorporate multi-fault rupture into seismic hazard models have often relied on empirical relationships, which are constrained by few M≥7.5 earthquakes, and multi-fault earthquakes have been largely ignored in probabilistic tsunami hazard models. Physics-based earthquake simulators like RSQSim — built on simple models of loading and stress transfer across a fault network — offer an alternative pathway toward identification of groups of faults that may rupture simultaneously in a multi-fault earthquake or closely spaced in time during complex earthquake sequences.

We present a 90 thousand-year synthetic earthquake catalog created using RSQSim and a 3D model of 469 crustal and subduction faults. We compare rupture connectivity of synthetic events in this catalog with the ruptures used as inputs for the 2022 Aotearoa New Zealand Seismic Hazard Model (NZSHM22). We find that: (1) Rupture connectivity of earthquakes in our synthetic catalog is high, with 46% of MW≥7.0 earthquakes rupturing multiple faults; (2) the longest earthquake ruptures in the synthetic catalog are significantly shorter than the longest ruptures in NZSHM22; and (3) inclusion of the Hikurangi subduction interface in the model increases rupture connectivity among crustal faults, but not the overall along-strike length of crustal ruptures. Further sensitivity testing is required, but initial models indicate that physics-based earthquake simulators represent a promising way to generate multi-fault earthquake inputs for seismic and tsunami hazard models.

Session: From Geodynamics to Earthquake Rupture, Models That Cross Time- and Length-Scales - I

Type: Oral

Date: 5/3/2024

Presentation Time: 04:45 PM (local time)

Presenting Author: Andrew

Student Presenter: No

Invited Presentation: 

Authors