Wellington tsunami evacuation FAQ
"In a long or strong earthquake, run past the blue line!"
Background
Wellington Emergency Management Office (WEMO) has the responsibility to make
warning arrangements for the city. GNS Science has modelled tsunami
evacuation zones in collaboration with Greater Wellington Regional Council, which
cover all sources of tsunami including mega-tsunami such as the March 2011
quake/tsunami in Japan. GNS Science also worked with local emergency
managers to help the Ministry of Civil Defence and Emergency Management
(MCDEM) publish nationally consistent tsunami evacuation zone, tsunami signage
and public alerting options guidelines. The information below is consistent with
these projects and guidelines, and also draws upon tsunami warning research
GNS Science has been involved with in New Zealand, Thailand, Indonesia, Hawaii,
the United States and Japan.
What is a tsunami?
A tsunami is a natural phenomenon consisting of a series of long surge-like waves
generated when a large volume of seawater is rapidly displaced. Tsunami are
known for their capacity to violently flood coastlines, causing devastating
property damage, injuries, and loss of life. In Japanese literally 'tsunami' means
'harbour wave'.
Huge submarine or coastal earthquakes, in which there is significant displacement
of the seafloor or coast, are the cause of most tsunami and cause the biggest
tsunami, in terms of wave height at shore and the size of affected area.
"A huge earthquake is one that is longer than a minute OR too strong to easily
stand up in."
Coastal and submarine landslides, and volcanic eruptions, can occasionally cause
tsunami too, but these affect a much smaller length of coast and are infrequent.
Because there is no felt earthquake associated with some landslides and
eruptions you should always evacuate if you see something strange in the ocean
(like the ocean receding or surf waves on a calm sea) or hear the roaring of a jet
engine from the sea.
Tsunami waves differ from ordinary coastal waves in that the entire column of
water from the ocean floor to the surface is affected. Tsunami waves contain
considerable energy. This means tsunami waves travel much further inland
compared to ordinary coastal waves. Tsunami also create other phenomena not
characteristic of ordinary waves, such as strong currents, and fast rising tides.
The first wave to arrive is often not the largest and there may be multiple waves
that arrive at the shore, each separated by up to an hour, or more. Waves may
keep coming in as a surge for minutes or tens of minutes, then rush out for a
similar length of time, before repeating the cycle. Waves may keep coming for
many hours.
How big or long an earthquake might cause a tsunami?
Long earthquakes can occur on the plate-boundary offshore, east of the North
Island. This is the same type of earthquake that produced the Indian Ocean 2004
and Japanese 2011 mega-tsunami. In this type of event, tsunami waves could
arrive at Wellington harbour in under 12 minutes.
Strong ground shaking indicates that the earthquake occurred very close. The
fault might have moved the seabed just offshore, causing a localised tsunami.
One such fault is the Wellington Fault. In this case, you may only have as little as
five minutes before the tsunami waves arrive at shore.
What is the blue line?
The blue line painted across streets in Wellington shows where the largest
tsunami might reach. Inland and uphill of the blue line is expected to be safe
from tsunami. In a huge earthquake run or cycle past the blue line. You shouldn't
simply stop at the blue line, but rather watch what is happening, head further
inland as needed.
Why shouldn't I wait for an official warning if I feel a huge earthquake?
The warning everyone has for a local source is the huge earthquake, you must
not wait to evacuate - a tsunami could be as little as 5 minutes away. Official
warnings are only able to be used for tsunami from further away.
"Immediately after a huge earthquake, scientists and emergency managers don't
have any more information about the possible tsunami than you do. Luckily you
have all the information you need - the huge earthquake"
In the short window of maybe 5-12 minutes after a huge earthquake before the
first waves of a tsunami may arrive no scientist, Council official or member of the
public will have more information than the huge earthquake everyone just felt.
There will be no extra information available within that timeframe to decide
whether to give an official warning.
How long after a huge earthquake will the tsunami arrive?
Arrival of the first waves may be as little as five minutes after the earthquake.
Five minutes is the minimum time from an earthquake you can't stand up in, if it
happens to have come from a fault just offshore of you. Waves may arrive after
only 12 minutes in an earthquake longer than a minute if it has come from the
plate-boundary. Unfortunately, there is no way of predicting if or how quickly a
tsunami could arrive. Either way, don't wait, immediately gather everyone in your
household and run or cycle past the blue line, don't drive.
Remember, once you have evacuated beyond the blue line it could be minutes, or
several hours, before the first or largest waves arrive, so stay away until being
given the official 'all-clear', which will be communicated through all available
means.
When should I evacuate?
You should evacuate immediately on foot or by bicycle. Only use a car if
absolutely necessary. If you must use your car, please do not stop at the blue
line - keep driving inland to make way for others evacuating along the same
route.
Once your neighbourhood is part of the tsunami blue line project, Evacuate past
the blue line if you feel a huge earthquake or if you are told to evacuate by an
official source. Otherwise, evacuate to high ground or inland outside of the
mapped coloured evacuation zones.
A huge earthquake is one that is longer than a minute OR too strong to stand
easily up in.
There are other natural signs of an arriving tsunami: You might see something
strange in the ocean (like the ocean receding or surf waves on a calm sea) or
hear the roaring of a jet engine from the sea. Evacuate immediately on
experiencing any of these signs.
Warnings from friends or neighbours might also be correct - if in doubt, evacuate
just in case. It's better to be safe than sorry.
Why should I walk, run or cycle past the blue line during a tsunami?
There isn't enough room on the roads for many people to use cars to evacuate in
the time before a tsunami may first arrive - in as little as 5 minutes. Traffic gridlock has been a major issue in previous tsunami, including Japan in the 2011
tsunami. Many people died when they were blocked from evacuating, when they
could have easily reached high ground by walking, running or cycling.
PLEASE! Leave the roads empty for the odd car that must be used to transport
people who are immobile.
If you must use your car, please do not stop at the blue line - keep driving inland
to make way for others evacuating along the same route.
Where should I evacuate from?
If you experience a huge earthquake, evacuate from all places below the blue
line. If your community is not part of the blue line project yet, know your
evacuation zones and evacuate from all zones in a huge earthquake. The largest
potential impact zone, which is marked by the blue line, starts at about 35m at
the coast and drops off inland.
Tsunami evacuation zones for the Wellington region can be found Evacuation
maps can be found on our Facebook page by clicking on the Tsunami Map
application here or at the Greater Wellington Website here
If the tsunami is coming from far enough away to give time for an official warning
you might get more detail, such as only to evacuate the beach (the red zone on
evacuation maps).
How do I find out how far inland a tsunami might go, and where is safe?
Tsunami might reach up to the blue line in places; that is into the red, orange and
possibly yellow zones on those maps. The blue line is painted at the outer edge of
the yellow zone, which is the maximum expected run-up height for tsunami. It is
expected to be safe inland and uphill of the blue line.
Evacuation maps can be found on our Facebook page by clicking on the Tsunami
Map application here or at theGreater Wellington Website here Find the map for
your neighbourhood, and make sure your whole family memorises it. The maps
are also included in tsunami information boards near the coast.
You shouldn't simply stop at the blue line, but rather watch what is happening
and head further inland as needed.
What are the blue lines based on?
The evacuation zones and blue lines are based on a review of credible sources of
tsunami that might affect Wellington. This review was carried out by GNS Science
and Greater Wellington Regional Council. They modelled the limit that all of those
sources, including the biggest credible mega-tsunami, could reach on land - this
mega-tsunami limit is the basis for the blue line. This mega-tsunami limit is
calibrated against real tsunami that have happened around the world and
computer models of future possible tsunami.
What are evacuation zones (red, orange and yellow)?
The red zone is the beach and foreshore and marine environment close to the
shore. If a tsunami is coming from far enough away, and there is time for official
warning, and the size of the tsunami will only be a hazard in the beach or
foreshore, then officials may only call for the red zone to be evacuated.
The orange zone was also modelled by GNS Science and Greater Wellington
Regional Council as the limit that most big tsunami from a regional (e.g. Tonga or
Samoa) or distant source (e.g. Peru) might reach. If a tsunami is coming from far
enough away, and there is time for official warning, and the size of the tsunami
coming is known to be smaller than the orange zone, then officials may only call
for the orange zone to be evacuated.
The outer edge of yellow zone is where the blue line is and represents the
maximum run-up height of a locally generated tsunami. In the event of a strong
or long earthquake, you and your household need to immediately evacuate past
the blue line or above 35 metres.
The GNS Science report report describing the modelling can be found at here
Can I trust a computer model to tell me where is safe?
For widespread, fast, effective evacuation the public need to know where is safe
and how to get there, there is abundant research across many hazards to show
this. The method used to draw the blue line is (a) conservative, (b) covers every
type of credible source including large mega-tsunami and (c) takes in data from
many past international tsunami as well as the results of computer models.
You shouldn't simply stop at the blue line, but rather watch what is happening,
head further inland as needed.
"The blue line is conservative and calculated by experts to cover mega-tsunami
like the one that hit Japan in 2011."
Why the blue line?
It is basically a sign, but because it is painted on the road and is a different colour
to other road markings it really catches people's eye. Tsunami evacuation zone
and route signage can be found around the world including the USA, Canada,
Chile, Japan and Thailand, to name a few places. Local residents in Wellington
developed the blue lines as a community initiative and it is the first place we
know of in the world to use a line across the road to educate this way.
As a result it has become the single most effective way of showing the most
important aspect of Wellington tsunami preparedness - where is expected to be
safe in a tsunami. Everyone is talking about the blue line: it has received positive
interest across the globe including in Samoa, the USA and Japan.
It is important that Wellington has a consistent approach that everyone
understands the actions to take in our city. That is why blue lines and other
appropriate tsunami signage will be going in all the tsunami risk areas; so no
matter where anyone is in the city, they know to what to do in the event of
tsunami - evacuate above the blue line.
Is the blue line high enough?
Yes. It covers all credible sources of tsunami from around the Pacific, including
the biggest ones - Plate Boundary fault-lines - that have created mega-tsunami in
the Indian Ocean in 2004 and Japan in 2011. We have one of these faults just
offshore of the east of the North Island, which may be able to generate a megatsunami of similar size. The blue line allows for these mega-tsunami. The blue
line has been designed to be safe in mega-tsunamis as large as the one in Japan.
You shouldn't simply stop at the blue line, but rather watch what is happening,
head further inland as needed.
Will the blue line affect my property value?
The blue lines in Island Bay have been in place for over a year and property
values have actually risen across Island Bay over that year. The blue line is a
world first, but it is effectively a sign marking a hazard zone and there are a
range of scientific studies that show hazard signs for tsunami and other lethal
hazards such as flooding and landslides do not effect property values. These
studies have been conducted in various countries, including New Zealand.
Tsunami evacuation zone and route signage can be found around the world
including the USA, Canada, Chile, Japan and Thailand, to name a few.
Is there enough time to evacuate past the blue line?
Every step counts. You will have at least 5-12 minutes after a huge earthquake
before the first wave arrives. This is enough time for most able people to walk,
run or cycle to the blue line or, at least, be well on their way. Remember, too,
that the further the water travels over land, the more it slows down.
It is always worth heading towards the blue line at any stage before a tsunami
arrives - you're never too late. The largest wave may come some time after the
first wave. Even the biggest tsunami won't reach the blue line in most places, and
every metre you run inland the tsunami will be shallower and slower. Leave
immediately after the earthquake, but if you are delayed you should still evacuate
past the blue line as soon as you can.
What if walking or running is not an option?
All of the people who are walking, running and cycling will leave the roads clear
for the odd car with immobile people that need to be driven.
If you have immobile people in your care, have this discussion now and make a
plan. Car-pool them as much as you can. Remember the tsunami might occur at
any time of the day, make sure you've allowed for a driver at all times.
After a huge earthquake, should I go into the evacuation zone to collect
my children from school or check someone has evacuated?
Don't go into, or return to, the evacuation zone after a huge earthquake.
Concentrate ahead of time on making sure everyone you care about knows to run
for the blue line the instant a huge earthquake has hit.
Think about it this way: if a lot of people go back in to the evacuation zone to
check that someone they care about has been evacuated, then more people will
be put in danger. This was one of the strongest recommendations from
emergency managers following the Japanese tsunami in 2011, they call it
'tsunami tendenko' - it encourages everyone to know what action to take in case
of tsunami and to practice these actions. Many people survived in Japan as a
result of following this advice. Have the conversations with your school ahead of
time and ensure you are comfortable with their evacuation procedures.
When is it ok to return below the blue line?
Only return to the evacuated area once you have received an official all-clear
from Civil Defence. Tsunami waves can take many hours to arrive and the largest
wave can be many hours after the first wave. Any huge aftershocks can generate
their own new tsunami.
Have tsunami hit Wellington in the past?
Wellington has a long human history of tsunami from both local and distant
sources. In 1855 an earthquake on the Wairarapa Fault caused a tsunami that
reached up to 10m above sea level in some areas around Cook Strait. In
Wellington this tsunami reached the interior of the Miramar Peninsula, and
probably crossed between Lyall and Evans Bays (an area that was uninhabited at
that time). Maori oral history also tells of a huge earthquake, which may well
have been accompanied by a tsunami, about 600 years ago. Tsunami caused by
distant earthquakes tend to be more frequent but less severe than ones caused
locally: examples include a tsunami in 1868, caused by an earthquake in Peru,
and ones in 1877 and 1960 caused by earthquakes in Chile.
It is likely that New Zealand has experienced tsunami larger than those recorded
in European or Maori history. Geological evidence of tsunami in Northland
suggests that a tsunami reached about 35m above sea level there - the cause of
that tsunami is not known for sure, but a large earthquake to the north of the
East Cape is a possible explanation.
Mega-tsunami, like the recent one in Japan, are infrequent events: the previous
mega-tsunami to hit most parts of the Tohoku region of Japan was in 869AD Japanese lived there at the time, but the lesson had been largely forgotten by the
time of the next mega-tsunami in 2011. We must not make the same mistake.
Why are there red, orange and yellow evacuation zones?
As well as the blue line painted across roads there are a set of nationallyconsistent evacuation maps with coloured zones on them. The blue line on the
road marks the inland edge of the largest yellow zone on the map.
If a tsunami is coming from far enough away and there is time for official
warning, and the size of the tsunami coming is known, then officials have the
option of calling for a red zone evacuation only, or a red and orange zone
evacuation. These smaller events are much more common than ones that reach
into the yellow zone, so it's important to avoid regular over-evacuation when
possible.
For example in New Zealand in the 2009 South Pacific, 2010 Chile and 2011
Japan tsunami the red zone (beach and foreshore) is all that would have been
needed to be evacuated. There was plenty of time for tsunami experts to reliably
work out the tsunami size and for official warnings to be able to say this.
If you feel a huge earthquake, you must evacuate all of the zones, head past the
blue line - there is no time to accurately estimate the size of the possible
tsunami, so there can be no evacuation order stating which zones to evacuate.
"Remember, in a huge earthquake evacuate all of the zones, get above the blue
line - there won't be time to give official warnings"
Why do the maps and signs look the way they do?
Evacuation maps and tsunami street signs follow a guideline and a standard
published by the Ministry of Civil Defence and Emergency Management, which
was produced by a working group of scientists and local emergency managers
from across the country. It drew upon expert advice and reviews of international
examples. The use of standard looking maps and signs means that if you learn
what the zones and signs mean in one place in New Zealand then you know what
to do anywhere else you go in the country. The signs are also consistent with
many Pacific countries, increasing the chance that tourists will know what to do
too when in these places.
I can see two blue lines on two different roads, and one seems to be at a
higher elevation, how can this be right?
Some of the tsunami modelling cuts through the middle of people's houses. In
some places, to avoid confusion, it is necessary to define the evacuation zones
around property and street boundaries so people can be sure about whether to
evacuate in an emergency or not. In the Island Bay pilot project, this led to a bit
of confusion on Tamar Street. This has since been recognised as an issue when
planning where the blue lines go in the future.
When are Wellington's civil defence sirens used?
Wellington has a number vehicle-mounted portable sirens and helicoptermounted public address units that will be used when a distant or regional-source
tsunami is coming (e.g. from Samoa or South America) It can take anywhere
from about 2 to 14 hours or more for tsunami from earthquakes not strongly felt
in Wellington to hit New Zealand. This provides WEMO enough time to activate
the mobile units once the tsunami threat has been confirmed and the Ministry of
Civil Defence & Emergency Management issues a warning.
Additionally, Wellington has a free Emergency Text Alert service that can provide
the public a quick head's up to any emergency event, which includes regional and
distant source tsunami. However, like all technology, it is susceptible to not
working when you need it most. This service is one more way WEMO will try to
provide an alert during an emergency. You can sign up for this free service by
following the directions on our Emergency Text Alert tab on our Facebook page
here
How can I help during a tsunami?
Knowing your neighbours and others on your street that might need additional
assistance is a great way to be of assistance during a tsunami and other potential
hazards. Make connections with these people and community groups as a way to
increase your community's resilience.
Make sure you plan evacuation with your family and neighbours before any
tsunami strikes. After a huge earthquake happens it's important that you don't
waste time before evacuating.
What have we learned from Japan in 2011?
In October 2011 GNS Science researchers interviewed local disaster prevention
officials and emergency services officials in seven heavily impacted communities
in the Tohoku region of Japan, in collaboration with local academics and
researchers. The focus of the research was to learn from the successes and
problems that occurred during the tsunami evacuation on 11th March 2011,
particularly related to the level of tsunami hazard awareness; response to natural
and informal warnings; function of official warnings; and use of vertical
evacuation buildings.
The research found that response to the natural warning of long earthquake
ground shaking of more than 2 minutes and immediate evacuation was vital in
saving lives. Official warning broadcasts caused confusion when broadcasts failed
due to power outages, and there was some public complacency following many
previous false alarms. Many deaths resulted from people delaying evacuation,
travelling into or through the evacuation zone unnecessarily, and trying to
evacuate by car. Many lives were saved when people took refuge in tall modern
buildings.