G25AP00449

Project title: Conditional probability of distributed surface rupture using the FDHI database.

Project period: 9/1/2025 through 8/31/2026.

Award purpose: Many critical and important facilities such as dams, powerplants, landfills, and buildings in the US are located near primary, active faults capable of producing earthquakes of engineering significance.

These facilities (generally speaking) are designed to perform well for expected ground motions, but have not been designed for permanent ground deformation due to earthquake surface-fault rupture.

With a growing number of detailed post-earthquake field surveys, however, there is abundant evidence that surface-fault rupture on secondary faults and shears can extend several kilometers from an active, primary fault.

This has led to the recognition that there is a non-zero hazard of surface fault rupture to facilities located near primary, active faults, and a newly recognized but uncertain risk of failure from permanent ground displacement.

Probabilistic fault displacement hazard analysis is a preferred tool to measure the hazard of fault displacement for critical and important facilities, as it casts the hazard in a framework suitable for risk assessment and performance-based engineering evaluation.

This project aims to improve the standard of practice for fault displacement hazard analysis by developing a new set of models that estimate the probability of surface-fault rupture at a site located off an active fault using a recently released, expanded database of historic surface-fault ruptures.

Activities to be performed: The project will build on existing methodologies and uses a significantly expanded database of well-mapped historic surface-fault ruptures and an efficient workflow using geographical information system (GIS) tools.

No new primary data will be collected and no fieldwork will be performed.

The first activity is completing the development of an automated GIS workflow using an industry and academic standard platform to efficiently process publicly-available surface-fault rupture trace data.

The resulting processed data will be evaluated to develop statistics on the patterns and frequency of distributed faulting away from principal ruptures.

These results will be fit to equations to predict the average behavior and uncertainties in the probability of a distributed rupture with distance from a principal fault rupture.

Coefficients will be developed to model the probability of distributed rupture based on factors such as style of faulting, building footprint size, and hanging wall or footwall location for dipping faults.

Deliverables and expected outcomes: The final technical report will document the objectives, approach, data inputs, and model results.

Results will consist of equation(s) expressing the conditional probability of distributed displacement for a site located away from an active fault and tables of coefficients to be used with the equations.

Uncertainties in the results will be captured in the form of standard deviations of sets of coefficients for different uncertainty percentiles.

Additional electronic data products will be included to allow users to interrogate the results and develop alternative models for use in site-specific analyses.

We will publish our findings in a peer-reviewed, open-access journal and provide all supplemental data and tools as open-source products.

Intended beneficiaries: Owners and stakeholders of critical and important infrastructure such as dams, nuclear power plants, landfills, and buildings located near active faults that are vulnerable to the hazard of surface-fault displacement geoscientists and engineers.

Subrecipient activities: N/A

Lettis Consultants International

FUNDING OPPORTUNITY GOALS RESEARCH FOR NATURAL HAZARDS, ENERGY AND MINERAL RESOURCES, ECOSYSTEMS AND ENVIRONMENTAL HEALTH, AND WATER RESOURCES.

15.807 - Earthquake Hazards Program Assistance

USGS Office of Acquisitions and Grants [DOI - USGS]

California United States

State-Wide

USGS Earthquake Hazards Program External Research Support Announcement for Fiscal Year 2025 (G25AS00240)