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PSHA Study for the State of Hawai’i Based on Regionalized Seismic Source Characterization and Ground Motion Characterization Models

Description: 

The State of Hawai’i spans the range from high levels of seismicity and active tectonics located around the island of Hawai’i to more stable and quiescent seismicity located around the island of Kauai. Given the observed active tectonics, volcanism, and seismicity, the area around the island of Hawai’i has some of the highest seismic hazard ground motion levels in the United States. A regionalized probabilistic seismic hazard analysis (PSHA) study was conducted for 81 sites located across the state of Hawai’I using a standard state of practice PSHA methodology.

To support the PSHA calculations, an updated seismic source characterization (SSC) and ground motion characterization (GMC) model were developed. For the SSC model, both crustal faults and regionalized seismicity were included based on previous fault models and an updated seismicity catalog. Given the potential damage significance from mainshocks as well as aftershocks, the rates for the gridded seismicity sources were developed for both a declustered and non-declustered catalog (i.e., including aftershocks) as part of the SSC model. The spatial distribution of events was only based on the declustered catalog. For the GMC, an evaluation with observed strong motion recordings in Hawai’i was performed to select the appropriate ground motion models. As part of this evaluation both current crustal models and subduction models were evaluated given the observed depth of events in Hawai’i, spanning from shallow depths of <20 km to intermediate depths of 20 – 40 km. For the aftershock sources, adjustments were applied to the ground motion models to account for an expected reduction in ground motions from aftershocks relative to mainshocks. We will present the significant SSC and GMC regionalized model features, the deviations from the recently released Hawai’i USGS models, and discuss the overall results from this PSHA study.

Session: USGS National Seismic Hazard Models: 2023 and Beyond

Type: Oral

Date: 4/18/2023

Presentation Time: 10:30 AM (local time)

Presenting Author: Nick Gregor

Student Presenter: No

Invited Presentation: 

Authors