A Site-Specific Probabilistic Seismic Hazard Analysis on Oahu Island in Hawaii

Date: 4/26/2019

Time: 06:00 PM

Room: Grand Ballroom

We have performed a site specific probabilistic seismic hazard analysis (PSHA) for a site on Oahu Island in Hawaii. The seismic source characterization used in this analysis is based on the 1998 USGS seismic hazard model for Hawaii, described in Klein et al. (2001). Oahu is in a region of low seismicity, with the largest historical earthquake on Oahu being the 1871 Lanai earthquake, which has an estimated magnitude of 5.9. The event did extensive, but minor damage in Honolulu. Currently, the highest hazard regions in Hawaii are on the flanks of the active volcanoes on the island of Hawaii (Big Island). Most large historical earthquakes are associated with the rupture of the rift zones along the flanks of Mauna Loa and Kilauea. The Big Island is modeled with multiple zones, including the “flank zones,” source zones enclosing the caldera and rifts of Kilauea and multiple zones encompassing the Big Island, with the seismicity divided into shallow (< 20 km) and deep zones. As seismicity in Hawaii decreases with distance to the northwest from the active volcanoes, the rest of the Hawaiian Island chain outside the Big Island is modeled as a single source zone. For the source zones, we’ve used an updated earthquake catalog, including data from the 2018 eruption of Kilauea. This is over 20 years of additional data from that used in the 1998 USGS seismic hazard maps for Hawaii. For ground motion models, we utilized the NGA-West2 models for active crustal zones.  Additionally, we used the ground motion model of Wong et al. (2012), developed for deep earthquakes (> 20 km) based on stochastic ground motion numerical modeling calibrated with the Hawaiian strong motion database, and Atkinson (2010) developed  for both shallow and deep Hawaiian earthquakes using the Reference Empirical approach. The local seismic source zone controls the hazard for short periods (peak ground acceleration), while the long period (> 1 sec spectral acceleration) is controlled by the source zones of the Big Island, even though it is located close to 400 km from the project site.

Presenting Author: Mark Dober

Authors