UNITED STATES FAULT AND FOLD DATABASE UPDATE

In the 1990s, the USGS, partnering with geological surveys in Alaska, Arizona, California, Texas, and Utah, dedicated resources to support an ambitious vision to create a digital inventory of potentially active faults. Published paleoseismic and geologic research was synthesized over the next 12 years resulting in interactive Geographic Information System (GIS) and descriptive products for more than 2,000 reported Quaternary-age faults. This public-facing asset reports data, on a fault-by-fault basis, throughout the Western United States, including Alaska and Hawaii. The faults were originally mapped at scales of 1:250,000 or 1:100,000 resulting in a uniform national coverage that is spatially accurate at an eye altitude of about 75 or 30 miles in Google Earth, respectively.

Although the early design of the United States product was to address the needs of the geologic community, the database currently serves a wide variety of users including those performing seismic-hazard assessments. Seismic-hazard users define geometry and behavioral attributes for fault sources based on the database. The Global Earthquake Model project (GEM) recognizes this need on a global scale and similar products (developed for Argentina, Australia, Bolivia, Brazil, Chile, Columbia, Costa Rica, Ecuador, Italy, Japan, New Zealand, Nicaragua, Panama, Peru, and Venezuela) are to be consolidated into a global dataset. However, the United States fault database, which underwent minor revisions eight years ago and in 2010, remains the most detailed of all existing compilations; future improvements will provide important details to inform seismic-hazard models.

The fault inventory is currently under revision to showcase recent fault paleoseismic-site investigations. Improvements include more accurate fault and trench-site locations using the most detailed published mapping; relevant additions to attributes and bibliographies are included in the update. In addition to the original contributors, an additional five states have joined this effort to improve the database content.