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Seismic Hazards (workbook 4) (management of seismic hazards (prediction …
Seismic Hazards (workbook 4)
Earthquakes
Tsunamis
primary
ground shaking
ground rupture
subsidence
uplift
secondary
soil liquefaction
landslides, avalanches
tsunamis
fires
drowning
focus- the point in the earth's crust where pressure release occurs
epicentre- the point in the earth's surface immediately above the focus
shallow focus earthquakes account for 75% of all energy released- larger number of gentle
P-waves- fastest moving, travel through liquids and solids
S-waves- slower moving, cannot pass through liquids
love waves- ground shakes from side to side, cause lots of damage
rayleigh waves- very destructive, like sea waves
richter scale
moment magnitude scale
Mercalli scale
hazards
ground shaking- depends upon the magnitude, depth, the distance to the epicentre and the local geology
ground rupture- the visible breaking and displacement of the Earth's surface probably along a fault. Poses a risk to engineered structures e.g dams, bridges and nuclear power stations
ground displacement- the ground moves up (uplift) and down (subsidence)
liquefaction- occurs when soil is shaken violently and takes on the properties of a liquid
Boxing Day Tsunami 2004
epicentre off the west coast of Sumatra
Indo-Australian Plate subducts at 6cm per year beneath the Burma Plate
focus 30km below the surface
slip of 15m along a 1,600km faut
8-10 minutes
death toll of 220,000 in Indonesia- total estimate is 280,000
eight people died in Africa due to high waves
1/3 of the dead were children
4x more woman died than men
9,000 tourists died
1.8 million people displaced
significant loss of housing
diseases e.g malaria and cholera
management of seismic hazards
prediction
identify areas at risk
include monitoring groundwater
monitoring radon gas release
unusual animal behaviour
measure fault displacement
magnetic fields
works along fault zones e.g San Andreas
doesn't work along unknown fault zones
prevention
try to keep plates sliding past each other rather than 'sticking' and releasing
can include lubricating movement with water and oil
protection
understand earthquakes and the effects
identify the risk
earthquake resistant design
policies and practices
modify the human and built environment
USA- Federal Emergency Management Agency (FEMA)
hazard resistant design
large concrete weights on buildings to counteract force
large rubber shock absorbers in foundations
cross-brace structures to hold it together
MEDCs have more money than LEDCs
education
instructions issued by authorities
earthquake kits
earthquake drills in schools
supply list including food, torches, matches, toilet paper and fire extinguisher
e.g Japan disaster prevention day
American Red cross supply list
fire prevention
smart meters cut off gas if high magnitude EQ occurs
eg Tokyo gas company network
tsunami protection
automated systems give warnings
prevention walls of up to 12m
insurance
richer areas take insurance to cover damage
only 7% of houses in Kobe had insurance
Haiti Earthquake 2010
Caribbean country in the West Indies
poorest country in western hemisphere
long history of national debt, extreme poverty and poor housing
below poverty line- less than $2 a day
Junction of North American and Caribbean plates
between the Septenrional zone (North) and the Enriquillo-Platain system
epicentre 25km away from capital Port-au-Prince
7.0 Magnitude
13km depth
at least 50 aftershocks measuring 4.5
social
225,000 dead- Government accused of creating a higher figure than actual
2.3 million people homeless
all hospitals in Port-au-Prince destroyed
collapse in education system- 1,300 schools destroyed
lack of water supplies and sanitation
disease spread- 8,000 died of cholera outbreak
prison destroyed- 4,000 inmates escaped
economic
3,000 commercial properties demolished due to low construction standards
government and public buildings destroyed
infrastructure damaged
damage to communications infrastructure and telephone service
environmental
collapse in the water supply
management
short term
rescue
relief/aid
3,500 soldiers deployed
search dogs
removal of dead- burial in communal graves
long term
-by 2014, over 170,000 were still in displacement camps
23% were not in primary schools
70% lacked electricity
50% debris had been removed
new building codes
sustainable recovery