EQ1: Tsunamis Flashcards
What are tsunamis?
-A tsunami is a train of powerful waves caused by the release of seismic energy from a divergent plate boundary caused by either submarine earthquakes (most destructive), landslides and volcanic eruptions
What are the characteristics of tsunamis?
-they consist of seismic energy that travels through the whole body of water
-as they move towards land they gain height as the water gradient becomes more shallow, they are often low in height out of sea (300m)
- energy does not deplete as it reaches land)m
-there are usually a series of waves and the first wave does not necessarily have to be the largest or most destructive
-long wave length can mean up to an hour between waves
How are tsunamis formed?
1)Energy is released during an earthquake causing the sea floor to uplift, displacing the water column above
2)the water is dragged back down by gravity and the water splits into distinct waves travelling in all directions
3)as the wave travelled towards shallow shorelines it will slow down and increase in height of up to 30m
4)the wave can travel up to a mile inland
What was the 2004 Boxing Day tsunami?
A magnitude 9.1 earthquake generated a tsunami in the Indian Ocean which sent 10m high waves towards 14 countries
What were the impacts of the 2004 Boxing Day tsunami(3)?
-killed 300 000 people across 11 of the affected countries
-$9.4 billion in total damage
-counties like Thailand that heavily relied on tourism experienced a significant decline in visitors impacting the local economy
What were the most important factors impacting that increased the risk of the Boxing Day tsunami 2004 (4)?
-Due to low economic development, the Indian Ocean did not have a monitoring or warning system and therefore did not detect the earthquake or tsunami. This meant that no one knew a tsunami was travelling towards land so did not have time to evacuate from densely populated coastal areas which lead to increased death and destruction ($9.4 billion in total)
-Many of the affected countries are low lying islands which exacerbated wave height and increased the level of infrastructural damage
-Low levels of development also meant that many of the affected countries had a low level of education and did not know how to react or save themselves when the tsunami was heading towards land and much of the infrastructure was not built with protective measures e.g. when the tide went back instead of people evacuating to go to higher ground as it is a warning sign, many fisherman went to go pick fish
-If there had been a warning system, many deaths and could have been prevented. This is evident in the 2011 Japanese tsunami which was a similar magnitude event (9 on the magnitude scale) and only killed 20 000 in comparison.
What was the Japan 2011 tsunami?
In 2011 Japan was hit by a 9.1 magnitude earthquake that triggered a train of tsunamis
What were the impacts of the Japan 2011 tsunami ?
-The seismic energy released caused the Earth to spin on it’s axis and the World to lose 1.8 seconds of time
-around 20,000 people were killed or remain missing
-was the costliest natural disaster in the world ($235 billion worth of damage)
What was the most important factor/s increasing the risk of the Japan 2011 earthquake?
-the 9.1 magnitude
-Japan is one of the most prepared countries in the world against tectonic hazards due to the frequency of hazards they experience and the level of protection which is provided for the population e.g. they observe a natural disaster day on the 1st September every year and spend billions on building resistant infrastructure yet the sheer scale and energy of the tsunami still meant that around 20,000 people were killed or went missing
Why were there less deaths in the Japan 2011 tsunami then the 2004 one?
-Japan has detention systems and warned the entire population that a tsunami had been generated. This meant people could evacuate in time and take precautionary measures, resulting in a much lower death toll in comparison to the 2004 tsunami.
-However, the economic damage could not be avoided as the infrastructural damage was a result of the coastline sinking by 1m and the tsunami waves being so powerful they travelled over the tsunami sea wall defences
