JDFEM.com
Juan de Fuca
Emergency Management

South coast of Vancouver Island
BC, Canada
Tsunamis -- Juan de Fuca Strait

Worried about a tsunami?
Choose one or the other scenario. They are very different!

"The BIG ONE"
from our LOCAL quake

"The LITTLE ONE"
from a DISTANT quake

You just felt
3-4 minutes
of shaking
This is the Mag 9
super quake

You heard about
a distant quake and
tsunami in the news

Quickly check for serious injuries.

Do not use phones.
Leave them for emergency people

Do not expect much help
from 911, police, fire, ambulance,
BC Hydro, and so on for days
Go to the
Tsunami Warning Center

which is the original source
where the media and emergency programs
are getting their information.
If you live near the water
Know the following before the quake because afterwards the Internet may not work.
Know DEFINITION

WARNING
Advisory
Watch


15 minutes in Tofino
30 minutes in Port Renfrew
1 hour in Sooke
1 hour 15 minutes in Victoria
The tsunami will be fairly small ,
probably less than a meter
The tsunami will not affect you
unless you are in a
HIGH RISK AREA
close to the water

such as camping or living near the water

Make sure you are a safe height
above the water
-- See official zones
Do NOT go to the beach
to watch

You may get hurt, and you will be a nuisance
to emergency operations
and the police handling evacuations and road blocks.


Stay away from the water
for 1-2 days

Follow the progress
of the small tsunami

as it hits our coast and enters Juan de Fuca Strait.
There is a 15 minute time lag,

Computer simulations
These can show you beforehand what to expect
Is the TIDE high or low?.
A small tsunami at HIGH tide can drown people camping on the beach
The picture shows the Japan
tsunami hit first around low tide, '
but continued as the tide rose
.
See hint about Insurance

JDFEM.com -- Juan de Fuca Emergency Management resource pages -- TSUNAMIS

THE "BIG ONE"
Computer Simulations
Institute of Ocean Sciences tsunami website
Every image is one minute apart --- 12 Hours = total sequence.
Use "Animation" buttons to view action.
Use "Next" and "Back" buttons for tight control
1
Notice how few minutes it takes for the red tsunami to reach the outer coast, and the many reflections (meaning multiple peaks)

The red zone at the start is water lifted by the locked zone as the continental shelf lunges ~20 meters forward in about 15 seconds

It also gives an idea of the "epicenter" or moving locked zone, which is 1000 km long and 50-80 km wide.
2
Notice the length of a tsunami wave (the red patches), and how it bounces off one coast then another.

A bay may not have a tsunami for several hours, then in a few minutes the water rises very high, surprising people (watch in the simulations when a bay suddenly turns red).

The energy is absorbed bouncing around the gulf islands, so little gets to Vancouver.
3
CFB navy ships in Esquimalt Harbour have barely an hour after the shaking to get out in deep water before the tsunami hits, with very fast currents (the black lines in the simulations)

This shows how a Seiche (saysh) wave begins to surge in and out of the harbour, like sloshng water in a shallow pan. It will be like a high tide to a low tide and back to high tide in less than 30 minutes, with over 20 knot currents.

All small boats and docks will be damaged or destroyed. Navy ships may act like battering rams against their docks already weakened by the earthquake.
4
Victoria Harbour will get the first tsunami in about 1 hour and 15 minutes, then many other high surges because of Seiche waves like Esquimalt. However the surges will be broken up into separate resonances because of the narrow places.

Many docks and boats will also be damaged by the fast surging action, including Fisherman's wharf. Signs should warn all boaters and tourists to stay away from the docks and floating homes for 24 hours or more.

JDFEM.com -- Juan de Fuca Emergency Management resource pages -- TSUNAMIS

THE "BIG ONE"
When will it hit?
The following images are from the computer simulation done in 2004 of a Cascadia Mega-quake by Josef Cherniawsky and others at the Insititute of Ocean Sciences for the Coast Guard.
This will give an approximate time of arrival after the mega-quake for planning purposes.
Smaller tsunamis with smaller wavelengths will travel slower.
30 minutes
after START of shaking.

Neah Bay -- water beginning to rise

Most of JdF Strait -- water receding < 1 meter




Size of
earthquake area

--the contnental shelf
surging west and up
to create the tsunami
45 minutes

This is where the tsunami would be when first seen on Neah Bay real-time Internet because of the 15 minute data upload delay.

Port Renfrew -- water more than 1 meter and rising fast
1 hour

Port Renfrew
- water still peaking
Sooke -- Water rising and surging around Whiffen Spit
1 hour 15 min

Port Renfrew -- water rushing out
Sooke -- peaking
Esquimalt, Victoria -- water flowing in after receding
Port Angeles -- rising fast
1 hour 30 min

Port Renfrew -- water rushing in, 2nd peak coming
Sooke -- after peak, water high, beginning to flow out.
Esquimalt, Victoria-- peaking height but still rushing into harbours. Boats and docks a mess.
Port Angeles -- peaking and piling high into harbour
1 hour 45 min

Port Renfrew -- 2nd peak rushing in.
Sooke -- water low and rushing out
Esquimalt, Victoria-- beginning to recede
All harbours and bays -- tsunami sets up resonances in each harbour and bay, with peak timing and heights quite variable, often ~20 minutes peak-to-peak, and repeats for several days. Water can rush in suddenly for at least next 48 hours.

JDFEM.com -- Juan de Fuca Emergency Management resource pages -- TSUNAMIS

THE "BIG ONE"
The Tsunami in SOOKE

Computer Simulations show the tsunami will partially overflow Whiffen Spit at perhaps
HALF the height of the outside shore

A smaller amount of water gets through into Sooke Basin, A small surge at the far end will pile up higher in Roche Cove
The FIRST tsunami will arrive ONE HOUR
after the earthquake shaking stops,
followed by many other surges of different sizes

Outside Whiffen Spit it will be
around 1.3 meters,
or about 5 feet,
crashing against the rocky shore.
(The legend is in cm, 200 cm = 6.5 feet)
The tsunami will pile up higher against Whiffen Spit, and into the bays shown in the photo,
then will flow over the top of the spit and around the end
(more if at high tide)
,
Damage to Boats and Docks

After flowing over and around Whiffen Spit
,

there could be a meter or 3 feet of water surging through Sooke Harbour, churning up mud and damaging boats and docks.

Water going over the Spit will carry away all the driftwood logs (left), which can act like battering rams on boats and docks.
SIGNS should tell people

GET OFF THE SPIT

AFTER THE SHAKING

AND STAY AWAY FROM THE WATER
FOR 24 HOURS

JDFEM.com -- Juan de Fuca Emergency Management resource pages -- TSUNAMIS

THE "BIG ONE"
How big will the tsunami be where you live?
The BC shoreline has been divided into zones based on expected tsunami height.
Wave height represents the best consensus of scientific estimates of wave height at this time.

2x the wave height gives the expected maximum "runup" or height of destruction.

3x the wave height gives the expected "safety" level where people can be evacuated to, and they can stand safely watching the destruction. Planning level allows for subsidence.(see diagram below)

However, observations of real tsunamis show the runup can vary greatly depending upon topography.Click on the picture at right to see how runup varies on the two sides of the valley in Japan, and the varying height on the right. The variable and unpredictable runup suggests it's good to have an extra margin of safety.
Official heights for planning -- pdf
PLANNING FOR HIGHER SAFETY MARGINS IS CHEAP INSURANCE

JDFEM.com -- Juan de Fuca Emergency Management resource pages -- TSUNAMIS

THE "BIG ONE"
When is it safe to visit the shore?
Pattern of tsunami waves shown by Tide Gauges
A single wave through water spreads into a "wave train"--->
and also reflects off the shores, and refracts (bends) around shallow water


The Japan 2011 tsunami that DID arrive
...

Despite the ridicule of many people, and the media saying it was a false alarm, the Japan tsunami was a very real.
  • It was 8 feet high in Crescent City, California, where it did damage and drowned one person who came to look.
  • It surged around harbours for more than 2 days...,
    • Reflecting off coast lines of Vancouver Island and Washington State
    • Seiche wave in harbours, like water sloshing back and forth in a shallow pan
It was also a wake-up call for such things as...
  • Communicating at night with distant locations, including people camping on high-risk beaches with poor access
  • Siren operations
  • Keeping the public including surfers away from beaches
  • Evacuations -- who, when, where, how...
  • Response in the middle of the night
See the Tide Gauge records below as proof of the Japan tsunami



Western Canada (List)

Vertical lines represent 3 hours each
Tofino
= + / - about 0.6 m max, or 1 foot up and down from normal for more many hours


Vertical lines represent 3 hours each
Victoria
= + / - about 0.3 m max, or ~6" up and down from normal, for more many hours...



American tide gauge sites from NOAA

Notice how many highs and lows there are, and large tsunamis may come hours after the first!

Vertical lines represent 12 hours each
NEAH BAY (opposite Port Renfrew)

Vertical lines represent 12 hours each
PORT ANGELES (opposite Sooke)


JDFEM.com -- Juan de Fuca Emergency Management resource pages -- Radiation


Causes of Tsunamis
An excellent YouTube video which clearly shows how the subduction zone causes a tsunami.
View in "browser" if it works.

Tsunami Insurance?
Homeowners can get EARTHQUAKE insurance fairly cheaply (~ $100 / year ).

It is cheap because there is a very high deductible.

It is worth every penny because a house twisted out of shape or shfted off a foundation can be worthless and have to be torn down, leaving you out a few hundred thousand dollars.

Homeowners can NOT get TSUNAMI or FLOOD insurance in Canada.
Flood insurance in the US is only available because the federal government subsidizes it.

So.....this hint might work
If your house or other buildings are in a high-risk tsunami zone, and will be washed away by a major tsunami, then AFTER the quake take some quick photos of the quake damage.

Then run or drive to a safe evacuation height where you can watch your house being washed away.

Afterward, you have proof of earthquake damage to show the insurance company that your house was badly damaged by the quake, before the tsunami,. You should get paid for the earthquake damage, even though your house is now floating out in the Pacific.

JDFEM.com -- Juan de Fuca Emergency Management resource pages -- TSUNAMIS

FOR DISTANT QUAKES
Definitions are important to avoid over-reaction
Watch -- A distant quake produced a tsunami that might be a problem in a few hours
Advisory -- A distant quake produced a tsunami that will affect our area but scientists are still monitoring how important it will be.
Warning -- A distant quake produced a tsunami that is coming in a few hours, so start evacuating low areas, and turn on the sirens. A small tsunami, expecially at high tide, can drown people around beaches, and sweep them away.
Tsunami Watch - is issued to alert emergency management officials and the public of an event which may later impact the watch area. The watch area may be upgraded to a warning or advisory - or canceled - based on updated information and analysis. Therefore, emergency management officials and the public should prepare to take action. Watches are normally issued based on seismic information without confirmation that a destructive tsunami is underway.

A typical WATCH email from the Alaska Centre.
"A TSUNAMI WATCH MEANS... ALL COASTAL RESIDENTS IN THE WATCH AREA SHOULD PREPARE FOR POSSIBLE EVACUATION. A TSUNAMI WATCH IS ISSUED TO AREAS WHICH WILL NOT BE IMMEDIATELY IMPACTED BY THE TSUNAMI. "
Tsunami Advisory - is issued due to the threat of a potential tsunami which may produce strong currents or waves dangerous to those in or near the water. Coastal regions historically prone to damage due to strong currents induced by tsunamis are at the greatest risk. The threat may continue for several hours after the arrival of the initial wave, but significant widespread inundation is not expected for areas under an advisory. Appropriate actions to be taken by local officials may include closing beaches, evacuating harbors and marinas, and the repositioning of ships to deep waters when there is time to safely do so. Advisories are normally updated to continue the advisory, expand/contract affected areas, upgrade to a warning, or cancel the advisory
.
A typical ADVISORY email from the Alaska Centre.
"A TSUNAMI ADVISORY MEANS THAT A TSUNAMI CAPABLE OF PRODUCING STRONG CURRENTS OR WAVES DANGEROUS TO PERSONS IN OR VERY NEAR THE WATER IS EXPECTED. SIGNIFICANT WIDESPREAD INUNDATION IS NOT EXPECTED FOR AREAS UNDER AN ADVISORY. CURRENTS MAY BE HAZARDOUS TO SWIMMERS... BOATS... AND COASTAL STRUCTURES AND MAY CONTINUE FOR SEVERAL HOURS AFTER THE INITIAL WAVE ARRIVAL."
Tsunami Warning - a tsunami warning is issued when a potential tsunami with significant widespread inundation is imminent or expected. Warnings alert the public that widespread, dangerous coastal flooding accompanied by powerful currents is possible and may continue for several hours after arrival of the initial wave. Warnings also alert emergency management officials to take action for the entire tsunami hazard zone. Appropriate actions to be taken by local officials may include the evacuation of low-lying coastal areas, and the repositioning of ships to deep waters when there is time to safely do so. Warnings may be updated, adjusted geographically, downgraded, or canceled. To provide the earliest possible alert, initial warnings are normally based only on seismic information

This was a WARNING email for Japan sent from the Alaska Centre.
"A TSUNAMI WARNING MEANS... ALL COASTAL RESIDENTS IN THE WARNING AREA WHO ARE NEAR THE BEACH OR IN LOW-LYING REGIONS SHOULD MOVE IMMEDIATELY INLAND TO HIGHER GROUND AND AWAY FROM ALL HARBORS AND INLETS INCLUDING THOSE SHELTERED DIRECTLY FROM THE SEA. THOSE FEELING THE EARTH SHAKE... SEEING UNUSUAL WAVE ACTION... OR THE WATER LEVEL RISING OR RECEDING MAY HAVE ONLY A FEW MINUTES BEFORE THE TSUNAMI ARRIVAL AND SHOULD MOVE IMMEDIATELY. HOMES AND SMALL BUILDINGS ARE NOT DESIGNED TO WITHSTAND TSUNAMI IMPACTS. DO NOT STAY IN THESE STRUCTURES. ALL RESIDENTS WITHIN THE WARNED AREA SHOULD BE ALERT FOR INSTRUCTIONS BROADCAST FROM THEIR LOCAL CIVIL AUTHORITIES. A TSUNAMI HAS BEEN RECORDED."
JDFEM.com
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