Summary

The northern Walker Lane of northeastern California and western Nevada is a region of significant earthquake hazard where major active fault systems intersect with population centers and critical water, power, and transportation infrastructure. Historic and geologic records document earthquakes approaching magnitude 7, and the 2023 U.S. National Seismic Hazard Model indicates a high probability of damaging earthquake shaking within the region over the next 50 years. Yet compared with other parts of California, many seismic sources remain poorly characterized, monitoring is relatively sparse, and substantial uncertainties persist in fault geometry and connectivity, paleoseismic parameters, seismicity, strain accumulation, site conditions, and expected ground motions.

These knowledge gaps are particularly consequential because significant water and power infrastructure lies within and adjacent to the active fault systems of the northern Walker Lane. Major dams and reservoirs, hydroelectric facilities, transportation corridors, water conveyance systems, and other lifelines are exposed to fault rupture, strong shaking, liquefaction, landsliding, and related earthquake hazards. The region also crosses the California–Nevada border, creating scientific, monitoring, infrastructure, and emergency-response challenges that require coordination across institutions and jurisdictions. 

The new Sierra Earthquake Risk Reduction Technical Activity Group (SiERRa-TAG) will brought together earthquake scientists and engineers with utilities, federal and state agencies, and local stakeholders to address these interconnected challenges. The TAG effort will focus initially on the central and northern Walker Lane, strengthening connections among communities that have not historically been closely integrated within SCEC while identifying multidisciplinary research that can improve earthquake hazard and risk assessments for the region. The inaugural SiERRa-TAG workshop reviewed ongoing earthquake-hazard research, assessed the state of knowledge and key uncertainties, and identified priority studies with the greatest potential to improve regional seismic hazard estimates and support water and power resilience. Technical presentations, a field trip to active faults and critical infrastructure, and interdisciplinary working groups connected observations and models with engineering and stakeholder needs. Participants contributed to developing an actionable, multidisciplinary research plan; priorities for earthquake scenarios and associated ground-motion studies; and improved coordination for earthquake response across the northern Walker Lane.

Workshop Goals

The workshop established the scientific and collaborative foundation for SiERRa-TAG and developed coordinated priorities for reducing earthquake-risk uncertainties in the northern Walker Lane. Specific objectives included:

1. Assess the state of knowledge and critical data gaps. Review current understanding of active faults, paleoseismic parameters, seismicity, geodetic deformation, site conditions, ground motions, and infrastructure vulnerability, and identify uncertainties that most strongly affect regional earthquake-hazard estimates.
2. Identify priority multidisciplinary studies. Determine where coordinated geological, geophysical, geodetic, seismological, and engineering investigations can provide the greatest advances in characterizing seismic sources, ground motions, and earthquake impacts, including candidate sites for an initial multidisciplinary pilot study.
3. Connect hazard science with infrastructure and engineering needs. Bring together scientists, engineers, utilities, agencies, and local stakeholders to identify credible earthquake scenarios, relevant hazard products, and priority infrastructure systems for subsequent engineering and risk analyses. 
4. Strengthen regional earthquake-response coordination. Develop relationships, communication pathways, response plans, and data-collection priorities that can improve coordinated scientific reconnaissance and cross-border response following future Walker Lane earthquakes. 
5. Develop an actionable research agenda for SiERRa-TAG. Establish shared research priorities and a coordinated work plan that can guide future SiERRa-TAG activities, support improvements to community and national hazard models, and provide a foundation for future collaborative research proposals.