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Regionally Adaptable Ground-Motion Models for Subduction Seismicity in New Zealand

Description: 

The New Zealand National Seismic Hazard Model has undergone its first significant revision in 10 years, and a newly compiled high - quality ground - shaking motion database was built and comprises all the seismic events with Mw≥4 recorded across NZ since 2000 (Hutchinson et al., 2021). Beside this, significant improvements were also done on the evaluation of the local site parameters for stations within the national seismic network (Wotherspoon et al., 2022).

By exploiting this database, a new ground motion model (GMM) for subduction seismicity was developed for various intensity measures such as, peak ground acceleration and 5% - damped pseudo - spectral acceleration up to 10 seconds. Beside common predictors (e.g. magnitude, depth, distances, Vs30), additional parameters were added to quantify the distinct attenuation patterns of the seismic waves observed along and behind the Havre Trough - Taupo Rift for the Hikurangi subduction zone trench. We observed different trends in the residuals in these regions based on the hypocentral-depth location on the slab and three distinct attenuation coefficients were added for each region in accordance with the observed 3D attenuation. This delineation with depth of the ground motion despairs after 1 second while the effect of the attenuation is still being present but reduced at longer periods.

To capture the local site amplification along the sedimentary structures, the local site variability was constrained based on multiple site parameters (e.g. fundamental frequency of resonance. Additionally, epistemic uncertainty in regional source, path and site properties was constrained using a partially non-ergodic methodology.

The new GMMs have a robust performance compared to regional observations and their forecast capabilities of the different parameters are consistent with the ones computed using the selected GMMs. The subduction model is recommended for application to interface and inslab earthquakes with Mw ranging from 4 to 7.8, and rupture distance less than 500 km.

Session: Advances in Probabilistic Seismic Hazard Analysis and Applications

Type: Oral

Date: 4/19/2023

Presentation Time: 11:00 AM (local time)

Presenting Author: Elena Manea

Student Presenter: No

Invited Presentation: 

Authors