Updating the U.S. Geological Survey National Seismic Hazard Model for Alaska

Session: Forthcoming Updates of the USGS NSHMs: Hawaii, Conterminous U.S. and Alaska
Type: Oral
Date: 4/28/2020
Time: 11:30 AM
Room: 230 + 235
Description: 

The National Seismic Hazard Model for Alaska was last updated in 2007. Since then, abundant new geologic and earthquake data have been collected and published; here, we present our plans for including these data and models derived therefrom in the next Alaska NSHM update. On the source modeling side, we plan to update the earthquake catalogs and the declustering and smoothing methodologies used to create gridded seismicity forecasts for two classes of earthquakes: (1) shallow earthquakes not explicitly associated with crustal faults and (2) deeper earthquakes associated with subduction intraslab seismicity. For fault models, we are currently soliciting new information on active faults heretofore not considered, or updates to existing fault sources. We also anticipate utilizing slip rates (or deformation models) derived from GPS data, consistent with recent model updates for the Conterminous U.S. The 2007 Alaska model included along-strike variations in slip rate on the Denali-Totschunda and Castle Mountain fault systems. For this update we are considering application of the Uniform California Earthquake Rupture Forecast, version 3, inversion methodology as an alternate approach to modeling rupture rates. The Alaska-Aleutian subduction zone is the primary contributor to hazard in the southern part of the state. In addition to reevaluating the 2007 interface segmentation model in light of new data, we also plan on using the SLAB 2.0 model to constrain interface and slab geometry and to discriminate between slab earthquakes and those in the overriding plate in the earthquake catalog. On the ground motion modeling side, we anticipate inclusion of the new NGA-Subduction models (Bozorgnia et al., this session), which mark a significant step forward in modeling both slab and interface ground motions. NGA-Subduction includes improved site and deep basin response models, as well as support for 22 spectral periods as required by the latest U.S. building codes for computing design ground motions.

Presenting Author: Peter M. Powers

Authors