Saturday, September 07, 2013

NPM13: The USGS West Coast Tsunami Scenario Report



USGS Tsunami Report


# 7637


Large tsunamis are rare enough in the United States that most Americans give them little thought – they consider them to be disasters that only threaten the Far East or islands of the Western Pacific.


But as we’ve discussed before (see East Coast Tsunami Threats & Just A Matter Of Time), the coastal regions of the United States are not immune to these destructive tidal waves.


Earlier this week the USGS released a report detailing the likely West Coast impact of a tsunami generated by a 9.1 Alaskan earthquake – and the numbers are sobering.  


This from the USGS news release  Experts Team Up on Tsunami Resilience in California:


In this scenario approximately 750,000 people would need to be evacuated, with 90,000 of those being tourists and visitors. Additionally, one-third of the boats in California's marinas could be damaged or completely sunk, resulting in $700 million in losses. It was concluded that neither of California's nuclear power plants would likely be damaged by this particular event.


The study (below) also estimates damage to marinas, businesses and homes range between $3.5 billion and $6 billion, and as many as 8,500 could be left homeless.



The SAFRR (Science Application for Risk Reduction) Tsunami Scenario—Executive Summary and Introduction

By Stephanie L. Ross, Lucile M. Jones, Kevin Miller, Keith A. Porter, Anne Wein, Rick I. Wilson, Bohyun Bahng, Aggeliki Barberopoulou, Jose C. Borrero, Deborah M. Brosnan, John T. Bwarie, Eric L. Geist, Laurie A. Johnson, Stephen H. Kirby, William R. Knight, Kate Long, Patrick Lynett, Carl E. Mortensen, Dmitry J. Nicolsky, Suzanne C. Perry, Geoffrey S. Plumlee, Charles R. Real, Kenneth Ryan, Elena Suleimani, Hong Kie Thio, Vasily V. Titov, Paul M. Whitmore, and Nathan J. Wood

The Science Application for Risk Reduction (SAFRR) tsunami scenario depicts a hypothetical but plausible tsunami created by an earthquake offshore from the Alaska Peninsula and its impacts on the California coast. The tsunami scenario is a collaboration between the U.S. Geological Survey (USGS), the California Geological Survey, the California Governor’s Office of Emergency Services (Cal OES), the National Oceanic and Atmospheric Administration (NOAA), other Federal, State, County, and local agencies, private companies, and academic and other institutions.


This document presents evidence for past tsunamis, the scientific basis for the source, likely inundation areas, current velocities in key ports and harbors, physical damage and repair costs, economic consequences, environmental and ecological impacts, social vulnerability, emergency management and evacuation challenges, and policy implications for California associated with this hypothetical tsunami.


We also discuss ongoing mitigation efforts by the State of California and new communication products. The intended users are those who need to make mitigation decisions before future tsunamis, and those who will need to make rapid decisions during tsunami events. The results of the tsunami scenario will help managers understand the context and consequences of their decisions and how they may improve preparedness and response. An evaluation component will assess the effectiveness of the scenario process for target stakeholders in a separate report to improve similar efforts in the future.

Report PDF (2.6 MB)




An Alaskan quake isn’t the only seismic scenario that could bring a destructive tsunami to our shores.  The Cascadian fault off the Pacific Northwest has a long history of a producing major earthquakes, the last one in the year 1700.




The geological record indicates massive quakes have struck the region at least 7 times over the past 3500 years. Given enough time, another is sure to strike again.



While far less common that their Pacific counterparts, east coast tsunamis - by reason of geography, population density, and a general lack of public awareness - have the potential to be extremely dangerous as well.


Courtesy of a tweet from FEMA Director Craig Fugate last year I found this fascinating slideshow training presentation on the East Coast Tsunami Threat.


One of the slides in this 29 minute presentation shows that while they happen less often than Pacific tsunamis, historically the east coast death toll is almost as great as those from the west coast.




Depending upon the type of precipitating event (seismic activty, landslide, asteroid/meteor impact, etc) and the location, tsunami travel and warning times around the Atlantic will vary from minutes to many hours.



You can access current Tsunami warnings and arrival times at the  Pacific Tsunami Warning Center.



As far as what to do before a tsunami threatens, READY.GOV has a Tsunami Awareness Page with helpful hints.


With September being National Preparedness Month this is a good time to consider what disaster threats are likely, or at least possible, where you live and work and to make plans on how you would deal with them.


While it may seem unlikely that a tsunami will affect you or your region - this is just one of many potential hazards that may threaten you and your community - and they all require similar preparedness steps.


Knowing your local threats, whether they be tsunamis, forest fires, floods, earthquakes or hurricanes  . . . and then becoming prepared to deal with them, will provide you and your family the best safety insurance available.


For more information I would invite you to visit:






Note: I’m still away from my desk, and so my blogging schedule will be light until I return on Sunday.  I would invite you to visit Crofsblog, Virology Down Under, and FluTrackers for the latest infection disease news.