Tsunami inquiry
Introduction
False alarms for tsunami in New Zealand are a regular occurrence. It’s easy to become blase about the warnings. However, it is only a matter of time before New Zealand is struck by a catastrophic tsunami. Its position on the Pacific Ring of Fire makes it particularly vulnerable. They pose significant risk to life and property. Tsunami’s inevitability means that it’s important to mitigate these potential effects. It is impractical to hold a tsunami back. Through this inquiry we have found that the best solution is a mix of evacuating and improving/developing a warning system.
What is a tsunami
Just like normal waves tsunamis consist of moving energy through water. The difference is where that energy comes from. For normal waves their energy comes from the wind which limits its size and speed. For a Tsunami its energy comes from landslides, volcanic eruptions, meteors and most commonly earthquakes. This is where the tectonic plates shift. Releasing energy to the ocean's surface and making it rise. Because of gravity the rise in the ocean gets pulled down which makes the rise ripple out. Now the tsunami is formed. When a tsunami is far from shore it travels through the entire depth of the ocean but when it reaches shallow water that energy is compressed. The speed of the tsunami slows down whilst the mass of it rises.
What causes a tsunami
Tsunami can be caused by many different things. Tsunamis are mostly caused by earthquakes on convergent tectonic plate boundaries. Since 1900 over 80% of tsunamis have been caused by earthquakes. However it’s not only earthquakes that can trigger tsunamis. A tsunami can be caused by landslides, volcanic activity, certain types of weather and possibly near-earth objects such as asteroids and comets. Asteroids do not have to directly hit the water. They could explode above the water and cause a tsunami.
Plate tectonics
In order to understand the role of violent seafloor movement as a major cause of tsunamis, you need to understand plate tectonics. The earth’s surface is made up of a number of plates that contain both the continents and ocean floor. They move relative to each other at rates up to several inches per year. A plate boundary is the area where two plates come together. The way one plate moves relative to another determines the type of boundary. There are three different types of boundaries. The first one is spreading. Spreading is where two tectonic plates move from each other. The second boundary type is Subduction. Subduction is where the two tectonic plates move towards each other, with one plate sliding beneath the other. Then lastly the last type of boundary is Transform. Transform is where the two tectonic plates slide towards each other. However, out of all these subduction is the main cause of tsunamis.
After the tectonic plates have come in contact with each other they disturb large amounts of the ocean floor. This disturbance displaces and lifts the ocean surface creating a swell. This swell is the tsunami. It gets bigger and bigger as it heads inland.
Landslides, Volcanic eruptions and Meteors
Submarine landslides often occur during a large earthquake. These landslides can be underwater and near the water to create a large tsunami. During a submarine landslide the equilibrium sea level is altered by sediment moving across the sea floor. Gravitational forces then propagate the tsunami given the initial perturbation of the sea level. This is the same as a violent marine volcanic eruption that displaces the water column which generates a tsunami. However, above water landslides and objects from space can disturb the water from the surface. The falling debris displaces the water from its equilibrium position and produces a tsunami.
Numerical data
This pie chart above shows the different causes of tsunamis. As you can see earthquakes are the biggest cause of tsunamis. We know that if there is an earthquake we can predict a tsunami. Out of all of these different tsunami causes earthquakes are 72%. Other causes such as volcanic eruptions, landslides and objects from space aren’t as big of a cause as earthquakes. This means that if we can figure out how to mitigate earthquakes we are also mitigating 72% of tsunamis.
How have tsunamis affected people in the past?
In the past after the “Killer wave” destroyed food sources and coastal settlements, sweeping society changes emerged. In New Zealand this included the building of fortified hill forts (pā) and a shift toward a warrior culture. One of the most destructive tsunamis that hit New Zealand was triggered by the Tonga-Kermadec fault. This happened in the mid 15th century. It was soon followed by an enormous wave which was triggered by an exploding volcano. This volcano is called Kuwae, near Vanuatu. To get an idea of how serious this tsunami was, this volcano 1453 eruption triggered the last phase of worldwide cooling. This was called the “little ice age”.
Between 1998 and 2017 tsunamis all around the world have caused more than 250,000 deaths. This is not including more than 277,000 deaths due to the Indian Ocean tsunami in 2004.
Can tsunamis be predicted?
As we explained earlier earthquakes are the main cause of tsunamis. Earthquakes can’t be predicted. We can however predict a tsunami after an earthquake has occurred. Also, there are many ways that we can start predicting the likelihood of tsunamis occurring. One of these is that historical records show where earthquakes frequently occur. Which gives us an idea of where and when a tsunami will happen from past events. Plate tectonic theory also predicts where earthquakes will occur. However these cannot accurately predict where a tsunami will occur. Therefore tsunami prediction cannot be really accurate.
However tsunami waves act in a predictable manner. This is because the speed of a tsunami can change, based on the ocean depth. The deeper the ocean floor is the faster the tsunami travels. Nowadays there are sensors that are in the paths of a tsunami. These sensors measure its characteristics before it arrives at other coastlines.
Scientists are constantly trying to learn new ways to predict the behaviours of tsunamis. However, due to current technology tsunami data comes at us after the disaster and damage has been done. In a post-tsunami survey geologists measure a number of factors. Scientists are particularly interested in the inundation and run-up feature after a wave has struck land. Inundation is the maximum vertical distance above sea level that the waves reached. Inundation and run-up are often determined by measuring the distance of killed vegetation. Scattered debris along the land and eye witness of people that survived the tsunami. These different ways to predict tsunamis are really helpful for scientists. This is because geologists and scientists can start predicting the damage and places that tsunamis are most likely to happen.
Pacific tsunami warning centre procedures:
Pacific tsunami warning centre has 4 procedures for it. These are:
First step is to locate the earthquake.
Is it local or anywhere else?
Is it under or near the ocean?
Is it shallow or deep within the earth?
How big is it (the magnitude)?
The second step is to determine tsunami travel time?
Tsunami travel time is dependent on seafood depth.
We know the seafloor depth for around the whole world which makes it easier to predict how fast a tsunami could come.
Therefore once we know when and where an earthquake has occurred, we can determine when a tsunami will arrive at any coastline.
The third step is to check the sea level gauges for evidence of a tsunami:
Sea level gauges measure and record sea level at a given location using a pier.
Deep-ocean assessment and reporting of tsunamis buoys are a deep ocean pressure sensor-type of sea level gauge.
The fourth and final step is issue warning messages as appropriate:
If there is an earthquake in a PTWC (Pacific Tsunami Warning Centre) of responsibility and meets a magnitude threshold they will issue a tsunami message. Initial tsunami bulletins for Pacific rim earthquakes are issued in 10-20 minutes. For Hawaii however these warnings are issued within 2-5 minutes.
Biggest tsunamis recorded
Building on how Tsunamis have affected people in the past, we can look at some of the biggest tsunamis recorded. This will tell us how tsunamis have affected people in the past and give us ideas for possible solutions. Big island, Hawaii. This was the fifth biggest Tsunami recorded reaching a run-up height of 9m. Triggered on April 1, 1946 this Tsunami killed 159 people and caused major destruction destroying 1.300 homes. The fourth largest tsunami “Hilo Bay” also struck Hawaii on May 22, 1960. Killing 61 people even though it was 1.5m higher than the big island tsunami. Occurring on July 12, 1993 the Okushiri, Japan tsunami is the third biggest tsunami. Reaching heights of 31m this tsunami was a big step up from its previous contenders also killing 239 people. The indian ocean tsunami rolled over the coastlines of Sri lanka, Thailand and India. The run up height of this tsunami was 35m and killed just under 230,000 people. The biggest tsunami was recorded on July 8, 1958 in Alaska. Reaching a run-up height 524m you may think this tsunami had a large effect on humans. But you would be wrong, even though it was half a km high it only killed 5 people.
Positive effects
Many people believe that a tsunami is all bad and only negative things come out of it, but you would be wrong. “In general, the positive effects of Tsunamis include the redistribution of nutrients in the coastal region. The creation of new habitats, landscape changes and provision of new economic opportunities”.
Redistribution of nutrients
Probably the most important positive effect of a tsunami redistributing nutrients, let us explain. The tsunami waves lift sediment filled with nutrients. As the waves crash down it spreads the nutrients inland. These nutrients help to fertilise agricultural soil and help grow mangroves. Not only do tsunamis distribute nutrients inland but in oceans as well. “Tsunami waves help in propagating small animal species from one region to another”. An example of this is in the Malacca Strait near Sumatra and the Bay of Bengal. After Tsunamis events the amount of nutrients in the ocean increased by 3 to 5 times.
Creating landscapes
Another effect that tsunamis have is the ability to create landscapes. Some people see this as destruction but it really isn't. Tsunamis can either deposit large amounts of materials on shore or wash away rocks and sand. As Tsunamis deposit materials on shore they form sand laminae, dump deposits, ridges, mounds and boulder stacks, says Yonature.com.
As the tsunami wave rushes inland they wipe out. Coastal forests, grooves, potholes and leave impact marks. And in return create ramps, canyons, pools, cascades, sea caves, arches, whirlpools, raised platforms and truncated cliffs.
New economic opportunities
Another benefit is new economic opportunities. I said before that tsunamis clear land, when they do this creates opportunities for Architects and engineers. This will mean that they can design new buildings for the future. Whilst this may have a negative impact on the habitat and any plants or animals there is always change. A tsunami will change many different landscapes. So whilst one is being used in industrial or residential, another landscape will have those plants, trees and animals.
Negative effects
The impacts of a tsunami can be devastating. Killing almost 430,000 people since 1850 a tsunami is nothing to mess with. The many negative effects of a tsunami outway the very few positives making it a very deadly geohazard. The negative effects of a tsunami depend on the characteristics of the seismic events that generated it. Its size (magnitude), its distance from its root cause and finally the configuration of its bytheryum (depth of the water) are all factors of its danger.
Death
One of the biggest effects of a tsunami is impact on human life. Nearly 430,000 people have been killed since 1850. There is very little warning before a tsunami hits and many people are left to fight for themselves and at that point there isn't much hope. According to Japantoday.com when the water is 70cm up your body there is a 71% chance of survival. People living in coastal areas almost have almost no time to reach high ground and die. “An example of this is the 2004 Tsunami that struck South East Asia and East Africa killed over 31,000. People in Sri Lanka only, leaving 23,000 injured”.
Destruction
The initial wave of a tsunami is not what causes all the damage but the water behind it. When the wave crashes down the mass behind the tsunami is released. There is so much water and power that everything in it is either destroyed or picked up by the current and washed away. This means there are two destructive elements of a Tsunami. The smashing force of the wave and the mass of water behind it. Tsunami waves destroy buildings, cars, lampoles, boats. As they make their way inland they demolish trees, plants and any other structures in their path.
Disease
"A tsunami can cause many problems and diseases are another. As a tsunami crashes and destroys buildings and cars but also damages infrastructure such as sewage and drinking water”. It will then spread through the flood to any survivors or rescue teams. Thus creating and spreading many diseases. Anyone still alive needs to be aware of diseases such as malaria. Under these conditions it is difficult for people to stay healthy which makes it harder for diseases to be treated. This means more chaos and deaths.
Environmental impacts
Another negative impact of a tsunami is their major toll on the environment. Animals, insects, plants and trees are just some of what are destroyed and killed during a tsunami. A tsunami can completely change a habitat making it unrecognisable. Not only land animals, animals die but sea life as well. As discussed before tsunamis can damage infrastructure releasing sewage. This sewage pollutes the ocean killing lots of sea life. Another impact is the solid waste tsunamis hold. As you can see in this photo this waste has a huge impact on the environment picking it up and demolishing buildings.
Psychological effects
Victims of a Tsunami often suffer psychological problems due to its danger factor and effects. This can happen for weeks, years and sometimes a whole lifetime. A study on the Sri lankan Tsunami 2004 showed that survivors had PTSD (post traumatic stress disorder). 14% to 39% of these were children, 40% of adolescents and 20% of mothers of these adolescents were found to have PTSD 4 months after the tsunami says Sms.Tsunami-warning.com. In Perilya village 2,000 people died and 200 became homeless. And some of these survivors were still experiencing psychological problems after 2 years of the event.
Cost
After a tsunami hits with the damage comes a cost. The government will have to help aid and fund cities in need. United nations, community groups and donations may also help repair any cities in need. Funding will be needed for unsafe buildings, income replacements, waste and any other problems that need fixing. It is hard to determine the exact figure as it depends on the damage caused by the tsunami. “ Tsunamis produce very strong currents that do considerable damage and cause loss of life”.
Currents/expert opinion
When we contacted our expert we asked him what he thought was the worst impact of a tsunami. He believes that the current the tsunami produces is the most damaging effect. “Tsunamis produce very strong currents that do considerable damage and cause loss of life”. This current also adds to the damage factor of a tsunami, washing sewage and debris inland.
Our expert Willem De Lange:
Tsunami expert Willem De Lange has been working on tsunamis since 1981 (40 years), monitoring tsunamis activity in the ocean. He has also spent time advising civil defence. We found Dr Willem when browsing our topic on Stuff.co.nz. We were intrigued when he said “it’s very uncommon to have three tsunami occurring worldwide within 24 hours in different locations, but to have it being generated in one location is extremely unusual”. We wanted to learn more about tsunamis so we contacted Dr Willem and he replied with very good and resourceful information.
What are the possible solutions to mitigate the negative effects of tsunamis?
There are many different solutions to mitigate the negative effects of tsunamis. In this part of the report we researched and explained the different possible solutions to this problem.
First solution - Warning system:
The Tsunami Warning System is the first of two steps in developing a warning system for the Pacific countries. While this system provides each region with the information it needs to assess whether it is at risk from a Pacific-generated tsunami. Each of the pacific countries must develop a system to communicate the warning to the public. A country with a well instructed, readily executable warning system can take full advantage of that time made available to it. Before a tsunami strikes. On the other hand a poorly planned warning system can spell disaster. For example in New Zealand there are signs along the coastlines and beaches. These signs show the different hazard areas for a tsunami and where you are safe.
These tsunami warnings are sent straight to your mobile device and you will get a really loud noise when the message is sent to you. This message will have instructions on what to do and if you are in the danger zone.
Our expert Willem Delange also said that the best solution is having a good warning system. After a good warning system a good evacuation plan is part of the best solution.
Second solution - Planning land use:
Carefully planning land use based on local assessments of risks and vulnerabilities. Adopting changes in how tourist infrastructures are sited. Implementing environmental protection measures and appropriate building standards. This basically means that it’s sensible not to build large public buildings near or in tsunami hazard zones.
The good things about this solution is that there will be less destruction. Both financially and to members of the public that live in these tsunami hazard zones. If this is going to happen there will be a big turn in the building code and where you can build houses and public buildings.
The bad side of this solution is that it’s not cheap and not easy to relocate a mass of public buildings. People wouldn’t really be keen to leave their beautiful beachside homes which makes it harder for this solution to be the most effective.
Third solution - Make sure your home has been checked:
This solution is that an engineer comes and checks your home and advises you on how to make it more tsunami resistant. This doesn’t mean that it will be fully tsunami proof but it won’t get destroyed as much. If many people do this there would be less destruction of homes and loss of lives around the world. This solution, as How to protect your home from a tsunami mentions, is that there are many different ways that you can divert waves from your property. For example, Improperly built walls could make your situation worse. Have a consultation with a professional. This will reduce the risk that you and your family is in and also reduces the cost after the tsunami hits your home. Because if you have a structure that is not easy for a tsunami to destroy you wouldn't have to spend as much money to fix your home.
Fourth solution - Tsunami safehouse:
The underwater safe house concept is designed to allow water to flood the house whilst trapping air. This allows anyone in the building to float to the top where all the air is trapped. This safehouse will be accessible to all public but can only be accessed during a tsunami event. The safe house will have toilets, a kitchen and food. We can demonstrate how this solution works by using water and a glass. If we tip a glass upside down and submerge half of it into the water. The water in the glass will rise back up to its original sea level (half of glass) leaving the upper half free with air for anyone in the house to breathe.
To be accessed the safe house doors will need to be connected to a warning system. When the warning system detects a tsunami it will send a message that will open the doors. We also need to consider the cost of this solution. Millions of people are prone to a tsunami hit. A safehouse is not cheap, there are things to consider such as:
Building supplies.
Builders, engineers and architects.
Power.
Food and toiletry supplies.
Some to look after the safehouse.
Whilst these are the main costs it is very hard to determine the exact amount needed to fund this solution as the population in different countries vary but it will most likely be billions of dollars for them to be built. According to Redzone.co Chile and Peru, West Coast USA, Japan, and New Zealand are in the most danger to Tsunamis, because we are all coastal regions. As you can see New Zealand is in this list.but as we have a population of 4,850,931 it will be easier to fund this solution.
Fifth solution - Evacuation:
Evacuation can be successful if pulled off correctly. Organisations like Getready.govt.nz which recommended and helped create by our expert Willem De Lange. This program teaches people how to stay safe and get out fast using simple steps.
If you feel an Earthquake, sea a sudden rise or fall in sea level or hear unusual sounds from sea.
Drop and cover during the shaking once it's over, get to high ground fast.
And if you make it out they will send you a message via your phone to go back down or stay where you are. This solution can be difficult as may be things like buildings, unclimbable cliffs and other obstructions stopping us. it could take hours before we reach high ground and by that time we are either dead or severely injured. We can accomplish this by designing pathways that lead directly to the nearest safezone.
According to our expert Dr Willem De Lange this solution is most effective. “Civil defence has created a campaign called long or strong - get gone. This campaign works well advising people in Tsunami prone areas to get out fast to safety”.
Sixth solution - Changing building codes that address tsunamis:
As we have said previously in solution two we could change land use and move buildings prone to a tsunami. But what if we didn't have to move those buildings and instead rebuild and just change the building codes. Changing these codes would mean houses prone to tsunami will be destroyed and rebuilt into a tsunami resistant building. Whilst this solution does sound desirable we do need to take into account the cost of this solution. As this comes at a cost many people may not feel comfortable paying for their house to be rebuilt. To show you how big of a cost this could we have done some research into Mount Maunganui.
“The median house price in Mount Maunganui is $1,022,200.00”. I also gathered information from Stats.govt.nz which told that there are 3798 dwellings in Mount Maunganui that are prone to a tsunami hit. If we were to demolish all these houses we would be destroying $3.9 of property. And that figure does not factor in the cost of rebuilding all those structures. We're not saying that all those buildings should be torn down, but if they were all those buildings would have a better chance against a tsunami hit.
Seventh solution - Do nothing:
This solution means do nothing. No warning, no evacuation, just hoping that people will sort it out for themselves. We chose “do nothing” so we could compare it to all our other solutions and how it would look in our Pmi table.
A Tsunami is inevitable and the damage brought with it is huge and to do nothing the damage would be worse. In terms of a tsunami with damage comes costs, so even though we haven't done anything we still need to consider cleanup costs such as.
Paying people income.
Repairing structures.
Repairing infrastructure.
And these are just some of the costs. So even though we have done nothing the cost has been more than any other solution.
Conclusion
After looking into all the different possible solutions we have come to the conclusion that it is not one solution but a mix of them all. When we looked at our pmi table the two solutions that really stood out were the Warning system and evacuation. These two solutions can work very well together, let us explain. If we can develop a warning system alerts people via their phone the instant it knows of any tsunami activity. If this happens everyone in tsunami prone areas should have time to evacuate. Whilst these two solutions are the best we may need some of the other solutions like a safehouse in places where there is no high ground.