SEASIDE, OREGON

The city of Seaside, Oregon, is vulnerable to earthquake ground shaking and tsunamis due to the Cascadia Subduction Zone (CSZ): 

• Hazards: probabilistic earthquake ground shaking and tsunami 
• Buildings: 4,679 
• Transportation network: roads and bridges 
• Local population: 7,115 (2020 estimate). 
• Tourist population (peak summer): 
  • Daytime:20,000onasingleday. 
  • Nighttime: 10,000 on a single day

IN-CORE Technical Process 

• Includes the effect of earthquake damage to buildings on building egress time. 
• Incorporates the effect of earthquake-shaking- induced debris on tsunami evacuation. 
• Quantifies the impact of mitigation strategies on tsunami evacuation and life safety.

In the event of a tsunami and assuming a daytime population requires time to seek shelter (15 minutes for locals and 10 minutes for tourists), the annualized fatality risk (persons/year) is the combination of baseline tsunami fatalities plus those associated with building egress time and debris.

 For a 1000-year mean recurrence event, the addition of egress and debris increases the risk 8.3-fold over the baseline, state-of-the practice models. 

When compared to the status quo for a 1000-year mean recurrence event, we find a 65% decrease in annualized fatality risks when mitigation strategies (tsunami readiness, vertical evacuation, and seismic readiness) are employed. 

The findings aid understanding the tsunami evacuation modeling and provide better insight for decision makers and emergency planners in coastal communities.

Amini, M., Sanderson, D. R., Cox, D.T., Barbosa, A.R., Rosenheim, N. (accepted). “Methodology to incorporate seismic damage and debris to evaluate strategies to reduce life safety risk for multi-hazard earthquake and tsunami”. Natural Hazards. http://dx.doi.org/10.21203/rs.3.rs- 1862973/v1.