The New Zealand Velocity Model (NZVM) Version 2.0 and ground motion simulations of Hope Fault earthquakes

Ethan M. Thomson, Brendon A. Bradley, & Robin L. Lee

Published August 14, 2018, SCEC Contribution #8552, 2018 SCEC Annual Meeting Poster #287

This poster presents recent updates to the New Zealand Velocity Model (NZVM) for use in physics-based broadband ground motion simulation and scenario simulations of ruptures on the Hope Fault. The NZVM is based on the concept of embedding high-resolution regional models in a modular fashion within a lower-resolution 3D tomography-based velocity model for the shallow crust. This flexible and extensible approach allows new regional models to be incorporated within the NZVM as they become available. The NZVM Version 2.0 builds on Version 1.0 by incorporating seven recently developed regional sedimentary basin models, distributed throughout New Zealand, to supplement the existing Canterbury region model implemented in Version 1.0. Additionally, a Vs30-based near-surface geotechnical layer and a new basin-edge smoothing regime have been implemented.

Broadband ground motion simulations for scenario ruptures of the Hope Fault are presented as a test case to assess the new basin models. The Hope Fault is a strike-slip fault in the South Island that transects the Hanmer and Kaikoura Basins, which are explicitly modelled in NZVM Version 2.0. It is a major contributor to the seismic hazard in the region and has the second highest slip rate (~20mm/yr) of any South Island fault. Results of ground motion simulations for historic small to moderate magnitude (4.0<Mw<5.0) earthquakes are used to validate the velocity structure within the new basins characterised in NZVM Version 2.0. Numerous scenario source geometries involving multiple fault segments spanning from the Kelly Fault (a splay fault off the Alpine fault) through to the Jordan Thrust were considered. The scenarios varied from Mw 7.1 to a maximum magnitude of 7.7. Simulation results for the Hope Fault scenarios are compared with 14th November 2016 Kaikoura Mw 7.8 earthquake to compare their relative regional impacts.

Key Words
crustal velocity model, ground motion simulation

Citation
Thomson, E. M., Bradley, B. A., & Lee, R. L. (2018, 08). The New Zealand Velocity Model (NZVM) Version 2.0 and ground motion simulations of Hope Fault earthquakes. Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
Community Modeling Environment (CME)