Transcript Slide 1

• Movement/tremor in earths crust
• Starts with a slight shake, stops and then
• Length of shaking varies from seconds to
• Associated with plates boundariesparticularly subduction zones
• Huge stress and rock snaps along fault
• Energy released as seismic waves
A tremor or seismic wave caused by energy release along a fault line… due
to stress… causes after shocks.
90% are shallow focus (70km deep)
Intermediate and deep earthquakes – only at subduction zones – not as strong
Main areas at plate margins
1. Pacific Ring of Fire eg. Kobe 1995 = 5,000 dead – cost $31b
Chile 2010 magnitude 8.8
1. Mediterranean/Asiatic eg. Iran 1990 = 40, 000 dead
Turkey 1994 = 20,000 dead – cost $7b
Iran 2004 = 20,000 dead
Indian-Burma 2004 Earthquake and Tsunami – 230,000 dead
• Seismology the study of earthquakes.
• Seismograph Instrument used to detect,
measure & record seismic waves.
• Seismic waves.. Primary(P)  5km per sec.
through solid & molten material.(spring)
Secondary(S) 2.5km per sec. through
solid material. Right angle movt. (rope)
Surface- slow.. Move side to side.
Locating epicentre: Calculated by recording intervals btw. S & P waves at a
seismograph station, 3 times….. 3 circles drawn & pinpoint centre.
Magnitude: measured on Richter scale…. Each scale magnified by 10 for
ground motion & by 30 for energy levels.
Mercalli scale measures damage on a 12 point scale.
Predicting earthquakes…
1. Seismic gaps… fault lines that have been quiet for a long time, likely to
become active soon i.e. Patterns
2. Measure crustal stress levels – instrument placed in holes 1,5km deep can
measure stress levels
3. Ground tilting - lasers
4. Swarms of foreshocks and slow tilting of the land are indicators of a quake.
5. Animal behaviour is used but not accurate.
6. Dating : study where earthquakes have occurred and monitor for energy build
up & patterns.
• Earthquake effects:
• Death and destruction
• Liquefication e.g. Mexico City anf Los Angeles
• Migration – huge numbers displaced
• Disease due to burst water pipes etc
• Economic meltdown due to physical damage to
• Damage & injury depend on:
 Time of day: People indoors/outdoors, in traffic queue.
Pop. Density: larger the pop. the greater the casualties.
Type of structure: poorly built collapse easily.
Soil type: Liquification of sand & silt (saturated & particles seperate)… flows
when hit by seismic wave & destroys objects in its path.
Geology: Solid rock more resistant.
Magnitude & duration: stronger & longer- more damage
Distance from epicentre: Further away less damage.
Fire: gas pipes broken, electricity lines short,
Flood: pipes broken; (lack of water to fight fire)
Tsunami: ( a tidal wave) Focus under the ocean. Waves spread outwards at up
to 1000km/h.
Meets shallow water, piles up and creates waves up to 30m. Devastates coasts.
Eg. Indonesia 2004. Satellite images help predict arrival of a tsunami.
All items in houses should be fixed to walls and imovable
Rubber shock absorbers and springs for buildings called seismic isolators
Automatic shutters on windows to prevent flying glass and all windows
should be shatterproof
Flexible material that can sway should be used e.g. Reinforced Iron Bars
Every floor reinforced at corners so less likely to collapse
Open areas to evacuate fleeing pop.
Local emergency plan
Earthquake drill for the public
Tsunami 26th Dec 2004
Epicenter off the west coast of Sumatra, Indonesia.
depth of 30 km (19 mi) below mean sea level
caused plate shifting of up to 20 m
estimated 1,600 km of faultline slipped (or ruptured) about 15 m
along the subduction zone where the India Plate slides (or subducts)
under the overriding Burma Plate
• The earthquake was caused by subduction and triggered a series of
devastating tsunami along the coasts of most landmasses bordering
the Indian Ocean, killing nearly 230,000 people in eleven countries,
and inundating coastal communities with waves up to 30 meters
• Magnitude of between 9.1 and 9.3, second largest earthquake ever
recorded. This earthquake had the longest duration of faulting ever
observed, between 8.3 and 10 minutes. It caused the entire planet
to vibrate as much as 1 cm and triggered other earthquakes as far
away as Alaska
• sudden vertical rise of the seabed by several metres during the
earthquake displaced massive volumes of water
• In deep ocean water, tsunami waves form only a small hump, barely
noticeable and harmless, which generally travels at a very high
speed of 500 to 1,000 km/h
• In shallow water near coastlines, a tsunami slows down to only tens
of kilometres an hour but in doing so forms large destructive waves
• The wave reached a height of 24 m when coming ashore along
large stretches of the coastline, rising to 30 m
• the total energy of the tsunami waves was equivalent to more than
twice the total explosive energy used during all of World War II
(including the two atomic bombs
• (Tsunami)
• (Tsunami) (earthquakes)
• (all plate tectonics)
Haiti Earthquake
Haiti – Caribbean Island
Poorest Country in Western World
Population of 10 million
Most people live on less than $1.50 a day
12 jan 2010
Earthquake measuring 7.0 on Richter
• Killed 230,000 people
• Felt in neighbouring countries
• Caribbean Plate and North American Plate
• Caribbean plate moves 20mm eastwards
per year in relation to NAP
• Had not moved in 250 yrs so huge
pressure built up
• Shallow quake just 13km deep and 25km
fro capital of Port-au-Prince
222,000 people dead, 300,000 injured
1.3 million homeless
90% of buildings in capital destroyed
4000 inmates escaped from prison
Vital infrastructure destroyed including
hospitals, transport facilities and
communication systems
• Port was destroyed so had to use port in
Dominican Republic but connecting road
was blocked for 10 days
• Aftershocks hampered aid effort
• Government moved people out of the
capital where aid could be more effectively
• Aid was sent from around the world e.g.
Medical supplies, tents, clothes, water etc.
Long Term effects
• Economic devastation – 1 in 5 jobs lost
• Brazil donated $140m, UK $24 etc
• Shanty Towns in port-au-prince destroyed
so people returning to original villages left
years previously
• Economic cost close to $7b
• Severe outbreak of cholera