1. Will the scoping report include an earthquake evaluation of the site and rail links?
2. What tsunami damage is being planned for at the GPT site?
3. Are there any emergency preparations in Whatcom county for an earthquake similar to the one that hit Japan’s east coast on March 11, 2011?
4. Could all the coal pile end up in the bay after an earthquake?
The coastline of the northwestern U.S. and Canada is
bordered by an active subduction zone where the Juan
de Fuca plate is subducting, or being pushed, beneath
the North American plate. Currently, the subduction
zone is considered locked (that is, it is not slipping).
Strain is therefore accumulating on the locked
interface between the plates. Plate convergence is
estimated to be between 3 and 4 centimeters per year
and possibly as high as 5.8 centimeters per year (the
long-term geologically estimated rate).
The M9.0 Cascadia scenario is based on an
approximately 1,000 kilometer (620 mile)-long
rupture of the Cascadia subduction zone megathrust
fault. The rupture extends from Cape Mendocino,
California, to central Vancouver Island, Canada. This
scenario is based on geologic evidence that indicates
such ruptures occurred on the megathrust in the past:
The last rupture was on January 26, 1700. Geologic
evidence suggests that the average recurrence of
~M9.0 earthquakes along the Cascadia megathrust is
about 500 years, but recurrence intervals vary,
ranging from about 250 years to over 1,000 years.
The effects of these earthquakes include strong
ground shaking that goes on for several minutes,
subsidence and/or uplift of coastal areas, liquefaction,
and tsunami. Aftershocks will be both strong and
numerous (possibly M7 or higher).
Type of Earthquake
Most earthquake hazards result from ground shaking
caused by seismic waves that radiate out from a fault
when it ruptures. Seismic waves transmit the energy
released by the earthquake: The bigger the quake, the
larger the waves and the longer they last. Several
factors affect the strength, duration, and pattern of
The type of rock and sediment layers that the
waves travel through.
The dimensions and orientation of the fault
and the characteristics of rapid slippage along
it during an earthquake.
How close the rupture is to the surface of the
Figure 1. ShakeMap for a M9.0 earthquake on the
Cascadia megathrust. The black polygon offshore is
the modeled fault rupture for this scenario.
U N D E R S T A N D I N G E A R T H Q U A K E H A Z A R D S I N WA S H I N G T O N S T A T E
Modeling a Magnitude 9.0 Earthquake on the
Cascadia Subduction Zone off the Pacific Coast
Washington Military Department
Emergency Management DivisionPage 2 of 4 / 2012–2013
Subduction Zone Earthquakes: Subduction zone
earthquakes occur where the Juan de Fuca oceanic
plate is being forced under the North American plate.
An earthquake is produced when pressure that has
built up along this zone causes the plates to slip
suddenly and rapidly past each other. Shaking from
the M9.0 earthquake modeled in this scenario will be
felt over the entire region and may last for several
minutes. This event is similar to the 2011 Tohoku
earthquake and tsunami in Japan.
Aftershocks: Unlike deep earthquakes, such as the
M6.8 Nisqually earthquake in 2001, which usually
produce few or no aftershocks strong enough to be
felt, a M9.0 subduction zone earthquake will be
followed by thousands of aftershocks, a few of which
could be large enough to cause additional damage and
Other Earthquake Effects
Tsunamis: A M9.0 Cascadia subduction zone
earthquake is expected to generate a massive tsunami
that will reach the coast of Washington about 20 to 30
minutes after the earthquake; waves may continue to
strike the coastline for the next 12 to 24 hours.
(Tsunami waves will also travel across the Pacific
Ocean.) Delta failures and landslides caused by the
shaking may also create or amplify tsunami waves.
Liquefaction: If sediments (loose soils consisting of
silt, sand, or gravel) are water-saturated, strong
shaking can disrupt the grain-to-grain contacts,
causing the sediment to lose its strength. Increased
pressure on the water between the grains can
sometimes produce small geyser-like eruptions of
water and sediment called sand blows. Sediment in
this condition is liquefied and behaves as a fluid.
Buildings on such soils can sink and topple, and
foundations can lose strength, resulting in severe
damage or structural collapse. Pipes, tanks, and other
structures that are buried in liquefied soils will float
upward to the surface.
Artificial fills, tidal flats, and stream sediments are
often poorly consolidated and tend to have high
Landslides: Earthquake shaking may cause landslides
on slopes, particularly where the ground is watersaturated or has been modified (for example, by the
removal of stabilizing vegetation). Steeper slopes are
most susceptible, but old, deep-seated landslides may
be reactivated, even where gradients are as low as
15%. Catastrophic debris flows can move watersaturated materials rapidly and for long distances,
mostly in mountainous regions. Underwater slides are
also possible, such as around river deltas.
Figure 2. Tsunami damage at
Onagawa, Ishinomaki, after the
M9.0 Tohoku earthquake near
Japan’s east coast on March 11,
(Photo: NOAA/NGDC: Shunichi
BE PREPARED WHEREVER YOU ARE:
Develop a plan and a disaster
supply kit. When you’re
prepared, you feel more in
control and better able to keep
yourself and your family safe.
LEARN MORE ABOUT WHAT YOU
CAN DO: www.emd.wa.govPage 3 of 4 / 2012–2013
Hazus Results for the
Cascadia Subduction Zone Scenario
Hazus is a nationally applicable standardized
methodology developed by FEMA to help planners
estimate potential losses from earthquakes. Local,
state, and regional officials can use such estimates
to plan risk-reduction efforts and prepare for
emergency response and recovery.
Hazus was used to estimate the losses that could
result from a M9.0 earthquake on the Cascadia
subduction zone. Such an event is expected to
impact 23 counties in Washington. Among the most
affected by the earthquake are Clallam, Grays
Harbor, Jefferson, King, Mason, Pacific, and Pierce.
(These estimates do not include losses due to
Injuries: The number of people injured in this
scenario will be high. Estimates vary by location,
ranging from several dozen (as in Jefferson County)
to nearly 2,000 (in King County). Although many
of the injuries will not be life-threatening, people in
every county will require medical attention and,
in many cases, hospitalization. Potentially lifethreatening injuries and fatalities are expected; these
are likely to be more numerous if the earthquake
happens during the afternoon or early evening.
Damage: King County will have the greatest
number of damaged buildings (more than 130,000).
For other counties, the number is lower, but it often
represents a much greater proportion of the county’s
building stock (as in Clallam, Grays Harbor, Pacific,
and Mason counties). Most of the damaged
buildings will be residential, but the number of
commercial and industrial structures is also
extremely high. The degree of damage will vary,
but extensive damage to thousands of buildings is
expected in Clallam, Grays Harbor, King, Mason,
Pacific, and Pierce counties. Structural collapse
(complete damage) of thousands of buildings is also
expected (more than 3,000 in Clallam County).
Economic Losses Due to Damage: Capital stock
losses are the direct economic losses associated with
damage to buildings, including the cost of structural
and non-structural damage, damage to contents, and
loss of inventory. For this scenario, the estimates are
substantial, ranging from more than $78 million in
Jefferson County to over $3 billion in King County.
Income losses, including wage losses and loss of
rental income due to damaged buildings, are high:
King County alone accounts for over $1 billion.
Impact on Households and Schools: The number
of people without power or water will be highest in
King County (followed by Pierce, Grays Harbor,
Pacific, and Clallam). King, Grays Harbor, and
Pierce counties will have the highest number of
displaced households and individuals in need of
shelter. The functionality of many schools will be
seriously affected by the earthquake. In Pacific
County, functionality will initially be as low as 12%.
Debris Removal: Following this earthquake, debris
(brick, wood, concrete, and steel) will have to be
removed and disposed of. King County alone
accounts for more than 1 million tons, Grays Harbor
for 740,000 tons, and Pierce for 583,000 tons.
Estimates vs. Actual Damage: Although this M9.0
earthquake was modeled using the best scientific
information available, it represents a simplified
version of expected ground motions. The damage
CASCADIA SUBDUCTION ZONE SCENARIO EARTHQUAKE
End-to-end length of fault (kilometers) 1,100
Magnitude (M) of scenario earthquake 9.0
Number of counties impacted 23
Total injuries (*severity 1, 2, 3, 4) at 2:00 PM 7,534
Total number of buildings extensively damaged 43,681
Total number of buildings completely damaged 8,768
Income losses in millions $3,811
Displaced households 18,385
People requiring shelter (individuals) 11,630
Capital stock losses in millions $11,994
Debris total in millions of tons 5.68
Truckloads of debris (25 tons per truckload) 227,240
Table 1. Summary of significant losses in the M9.0
Cascadia subduction zone earthquake scenario. Among
the most affected counties are Clallam, Grays Harbor,
Jefferson, King, Mason, Pacific, and Pierce.
*Injury severity levels: 1—requires medical attention, but not
hospitalization; 2—not life-threatening, but does require
hospitalization; 3—hospitalization required; may be life-threatening
if not treated promptly; 4—victims are killed by the earthquakePage 4 of 4 / 2012–2013
resulting from an actual earthquake of similar
magnitude is likely to be even more variable and
will depend on the specific characteristics and
environment of each affected structure.
Other Tools: Community planners can also look at
how a large earthquake may impact local resources
and people’s lives and livelihoods. The following
graphs illustrate variations in such impacts: The first
shows the levels of shaking that residents are likely
to experience; the second shows the possible impact
on different services and business sectors. Note that
in King County, a greater number of residents will
be exposed to very strong shaking, whereas Grays
Harbor, Pacific, Mason, and Clallam counties,
although less populated, will experience even more
intense ground motions.
Figure 3. Number of residents and employees affected by the M9.0 earthquake projected for the Cascadia subduction zone.
Modified Mercalli Intensity (MMI) classes indicate peak ground acceleration (PGA) values and the impact of the shaking.
V. Rather Strong
(PGA 3.9–9.2 g)
Felt outside by most. Dishes and windows may break. Large bells ring. Vibrations like large train passing close to
(PGA 9.2–18 g)
Felt by all; people walk unsteadily. Many frightened and run outdoors. Windows, dishes, glassware broken. Books
fall off shelves. Some heavy furniture moved or overturned. Cases of fallen plaster. Damage slight.
VII. Very Strong
(PGA 18–34 g)
Difficult to stand. Furniture broken. Damage negligible in buildings of good design & construction; slight–
moderate in other well-built structures; considerable in poorly built/badly designed structures. Some chimneys
(PGA 34–65 g)
Damage slight in specially designed structures; considerable in ordinary substantial buildings (partial collapse);
great in poorly built structures. Fall of chimneys, factory stacks, columns, walls. Heavy furniture moved.
(PGA 65–124 g)
General panic; damage considerable in specially designed structures; well designed frame structures thrown out
of plumb. Damage great in substantial buildings: partial collapse. Buildings shifted off foundations.