Tohoku and What It Means for Cascadia

Many recent earthquakes that grabbed headlines occurred outside of Cascadia, in countries such as Japan (Tohoku, 2011), Chile and Haiti (2010) and Indonesia (Sumatra, 2004). These far-away events, while not a part of Cascadia’s history, can teach us what to expect from future earthquakes in our region and help us plan and prepare for them.


A catastrophic magnitude 9 earthquake hit the northeast coast of Japan on March 11, 2011. The quake and resulting tsunami killed more than 15,700 people and injured another 5,300. More than 4,600 went missing. The events destroyed or damaged buildings, roads, bridges and several reactors at a nuclear power plant. Electricity, gas and water supplies, telecommunications and railway service were disrupted. Economic losses were estimated at $309 billion.

What it means for Cascadia

The tsunami generated by the Tohoku quake hit Hawaii and the U.S. west coast but caused relatively minor damage that generally was limited to beach front and harbor facilities.

  • The Tohoku quake was on a subduction zone fault, almost identical to the Cascadia subduction zone fault that lies off the coast from northern California to British Columbia. The Cascadia fault last ruptured in 1700, and is capable of unleashing a tsunami every bit as powerful and devastating.
  •  As devastating as Tohoku was, Japanese building codes (more restrictive and expensive than U.S. codes) prevented greater destruction.
  •  The tsunami generated by the Tohoku quake, not the quake itself, was responsible for most of the deaths, injuries and property damage. The size of the waves (up to 33 feet or 10 meters) overwhelmed seawalls and other defenses. The only way to protect people in the tsunami’s path is to train them to evacuate to high ground when a warning is given. In the case of Tohoku, as in a potential Cascadia subduction zone tsunami, the warning is the earthquake itself.

More Tohoku resources

HAZUS Predicts Massive Damage From Seattle Earthquake

This past week, dozens of emergency managers, geologists and state and local preparedness planners gathered in Seattle at the 5th annual Hazus conference. FEMA’s HAZUS is a loss estimation modeling program for earthquakes and can help communites prepare for earthquakes. KOMO News wrote an article on potential damage from a Seattle Earthquake (click here to see the article).  CREW has used HAZUS to develop different earthquake scenarios that can be found here.

Slow “Earthquake” Occurring Now Beneath the Olympic Peninsula and Puget Sound

The expected 2011 episodic tremor and slip (ETS) event has done the unexpected by starting months early. These events happen in the deep part of the Cascadia Subduction Zone, “down dip” from the area where the Juan de Fuca Plate is completely locked against the North American Plate. These “slow earthquakes” reoccur every 14 months on average and have been remarkably consistent over the past decade. Another of these events was expected to begin in late October, early November 2011 but has begun months early. Details from the Pacific Northwest Seismic Network.

Japan Tsunami Fuels Sense of Urgency in Cannon Beach

Cannon Beach has been proactive on preparing for earthquakes, with a vital emergency preparations committee, leadership and citizens. Cannon Beach recently completed 2 important studies,  one on geotechnical conditions which confirmed weak soils at the existing city hall location, and another on tsunami evacuation simulation.  Please see more details from The Oregonian here.