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WITHDRAWN Subduction Zones in USGS National Seismic Hazard Models

Description: 

WITHDRAWN Shaking caused by subduction zone interface and intraslab earthquakes can be a large contributor to overall earthquake hazard in U.S. Geological Survey (USGS) National Seismic Hazard Models (NSHMs). Recent and ongoing efforts to characterize hazard from subduction zones across the U.S. and its territories have shown that it is difficult to apply the same earthquake rupture forecast (ERF) modeling techniques everywhere. Furthermore, ergodic global and regional partially non-ergodic ground motion models (GMMs) are often difficult to reconcile with local data that may not have been considered during GMM development. For example, in the conterminous U.S. NSHM, the slow-slipping Cascadia subduction zone is characterized by a reliable geologic and paleoseismic record of large, zone-rupturing earthquakes, but the earthquake catalog is depleted in M<8 events. The subduction zone ERF is therefore limited to large M8+ events and localized patches of low-rate subduction intraslab events. The complex and uncertain structure of deep basins in high exposure areas like Seattle required their careful consideration during development of the GMMs. In contrast, the fast-slipping Alaska-Aleutian subduction zone (AASZ) is constrained by a modest paleoseismic record; high slip-rates permit development of geodetically derived slip-deficit rates. The AASZ also includes a rich catalog of smaller earthquakes, so the ERF also includes gridded seismicity-based ruptures (M5-8). In the 2023 Alaska NSHM, regional partially non-ergodic GMMs for subduction interface events were found to be at odds with recent earthquake data and were therefore disregarded in favor of data-adjusted global models. Here, we compare the different subduction zones considered in the USGS NSHMs in terms of geometry, geologic and paleoseismic constraints on historic ruptures, and earthquake catalog rates. We also discuss ways to improve the consistent representation of epistemic uncertainty across subduction zone ERF and GMM components.

Session: Advancing Seismic Hazard Models [Poster]

Type: Poster

Date: 4/17/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Jason

Student Presenter: No

Invited Presentation: 

Poster Number: 55

Authors