Lecture 8- Tsunamis Flashcards
What three things typically generate tsunamis?
- Submarine Eq/ volcanoes
- Submarine/into sea landslides
- Comets or meteorite impacts
What is tsunami wave velocity a product of?
Earths velocity and sea depth
What is the equation linking amplitude and velocity?
A2V= constant
What happens to H and V as waves get progressively inshore?
H decreases ,which in turn causes a decrease in V and an INCREASE IN A
Essentially: the wave gets slower but taller
What is the typical velocity fo an offshore tsunami?
Up to 900km/hour
What is the average amplitude of an offshore tsunami?
<2m
What Is the average wavelength of an offshore tsunami?
Hundreds of Km
What is the average velocity fo a near shore tsunami?
Few tens of kms
What is the average amplitude of nearshore tsunamis?
Several tens of KM
What is tsunamirun-up?
The maximum height above sea level reached by tsunami waves as it rushes on shore
What is Unami inundation?
The horizontal distance reached by a tsunami, measured from the shoreline
Where do 59% of all earthquakes occur?
In the Pacific ring of fire
Where to 25% of tsunamis occur?
In the Mediterranean Sea
What are the three ways of reducing vulnerability to tsunamis?
- Hazard assessment (probabilistic forecasting)
- Land use planning +defence
- Education, planning, training
What magnitude earthquake “guarantees” a tsunami event?
> 6.5
What is issued when an earthquake magnitude 6.5 or greater occurs?
Bulletins
What is issued when earthquakes 7.1-7.5 occur?
Watch bulletins
What are dart bois?
Pressure recorders that are able to distinguish between long tsunami inundation and natural short wavelength ones
How many countries are covered in the Pacific Tsuanami waning system?
28
When was japans tsunami warning system established?
1952
How many people died in the 2004 Indian Ocean tsunami? Why?
290000+ as there was no early warning system
How quickly within a tsunami event does the Japanese tsunami warning system issue an alert?
Three minutes
When was the pacific tsunami warning system implemented, how many countries are included and how long does data analysis tke?
Established in 1949, includes 28 countries and takes 10-20 minutes to process data
Why does the tsunami blind zone occur in the pacific tsunami warning system?
Gaps in dart buoy distribution (particularly close to the coastline)
