RECENT EARTHQUAKE HAZARD MAPPING AND HAZUS DATA ENHANCEMENT STUDIES IN WASHINGTON STATE

Recent moderate to large deep and shallow (crustal), and historical large and megathrust (subduction) earthquakes in western Washington and Oregon give rise to the high probability of future earthquakes. This high probability of earthquakes in the region requires better state, county and community preparation to mitigate future losses. We are providing earthquake site class and liquefaction susceptibility maps to give more detailed near-surface geological information for statewide seismic hazard and building code maps. To produce these maps, we have been conducting shallow shear-wave velocity (Vs) seismic surveys and compiling it in an accessible database, as well as paleoseismological trench studies, geologic quadrangle mapping, and creation of a landslide database in Washington.

These data can be used in the HAZUS MH software distributed by FEMA for earthquake modeling to prepare state and county mitigation and emergency response plans. However, the current default (Level 1) Washington State HAZUS data distributed by FEMA have been outdated. To enhance (or update) the HAZUS data, we recently launched a HAZUS Data Enhancement project, funded by the Washington Military Department – Emergency Management Division (EMD), which will provide updated inventory data to for better earthquake loss estimations and emergency response practices. Our initial effort has shown that the source data to update the HAZUS statewide (Level 2) database are complex and cannot be directly used in the HAZUS earthquake modeling, unless prior editing and appropriate updating procedure are employed. In our data enhancement project, we use a four-step HAZUS data updating procedure: 1) Data collection, 2) data preparation, 3) data entry (updating the HAZUS data), and 4) testing the updated data. The Comprehensive Data Management System (CDMS) tool recently distributed by FEMA is selected for the database update process. A general flow chart model summarizing our geologic field work for earthquake hazard mapping to inventory data collection efforts for earthquake risk analysis will be presented with examples of selected counties in western Washington. The updated inventory coupled with improved geologic, seismic and geotechnical data will lead to more robust hazard and risk analysis than has previously been available.