seismic hazards

Question 1

how seismic hazards occur

Answer 1

• they occur along all plate boundaries as they become stuck due to friction
• when plates are stuck the convection currents continue to push which builds up the pressure
• this pressure gives way causing a jolting motion which causes seismic waves

Question 2

p waves=

Answer 2

primary waves travel the greatest velocity through the earth

it moves the ground back and forth

Question 3

S waves

Answer 3

secondary waves which are slower

they cause the most amount of destruction as the crust moves from side to side

Question 4

surface waves

Answer 4

there’s 2 types of waves:
love waves=they move the ground side to side
Rayleigh waves= roll along the surface

Question 5

magnitude=

Answer 5

measured in a variety of ways:

• THE RICHTER SCALE= logarithmic scale measures from 1-10. each number is 10 times greater than previous number
• more common to be measured using the MERCALLI scale which measures intensity and impact- its subjective as its dependent on human development rather than the stength

Question 6

distribution=

Answer 6

occurs along all plate boundaries
most powerful along destructive margins
conservative margins are marked with a fault which produces the earthquake

Question 7

frequency=

Answer 7

they are frequent and occur everyday but hundreds cannot be felt by humans

Question 8

regularity

Answer 8

earthquakes follow no pattern and are random

Question 9

predictability

Answer 9

almost impossible to predict

SEISMIC GAPS= areas that have no experienced an earthquake for sometime and are overdue one

Question 10

primary effects=

Answer 10

GROUND SHAKING= horizontal and vertical movement of the ground. the severity depends on the magnitude, geology and distance form epicentre
GROUND RUPTURE= the visible breaking and displacement of the earths surface especially on the fault lines due to seismic tremors- there a risk to bridges and nuclear power stations

Question 11

secondary effects

Answer 11

LIQUEFACTION= earthquakes occurring on geology which has a high water content and consists of sand causes a solid to act like a liquid causing buildings to collapse and sink
LANDSLIDES AND AVALANCHES=earthquakes in mountainous regions often cause landslides which cause roads to become blocked and create a flood risk
TSUNAMIS= when the oceanic crust is jolted it displaces water. as it gets closer to the coast the sea level decreases so there’s friction between the sea bed and the waves causing the waves to slow but gain height

Question 12

general primary impacts

Answer 12

ENVIRO- fault lines destroy environment
ECONOMIC- destroys businesses
SOCIAL- buildings collapse which kills people
POLITICAL- government buildings destroyed

Question 13

general secondary impacts

Answer 13

ENVIRO- radioactive materials leak and salt water floods freshwater
ECONOMIC- decline of business, high cost of rebuilding
SOCIAL- gas leaks can cause fires and there’s a spread of disease
POLITICAL-borrowing of money for aid, looting and political unrest

Question 14

prevention

Answer 14

they can’t be prevented but the risk can be reduced such as liquefaction through soil stabilisation

Question 15

preparedness

Answer 15

• authorities can install earthquakes with warning systems via the tv and radio
• tsunami warning systems and evacuation routes can be set up
• communities can set up search and rescue teams to tackle impacts

Question 16

protection

Answer 16

HAZARD RESISTANT STRUCTURES- concrete weights on top of buildings can help counteract the stress and rubber shock absorbers
RETROFITTING- devices used to make more earthquake proof
EDUCATION- evacuation drills, kits and supplies kept at home
FIRE PREVENTION- smart meters cut off gas
LAND USE PLANNING- most hazardous areas identified and regulated places such as schools and hospital put in low risk areas

Question 17

Haiti background information

Answer 17

January 2010
7.0 magnitude
epicentre 25km fro port au prince
GDP of $1,200 /person
Port au Prince is on a fault line and at risk of tropical storms- in 2008 a storm killed 800 people (2 years before)

Question 18

HAITI impacts

Answer 18

• 316,000 people died
• 2.3 million made homeless
• housing built poorly in shanty towns
• ports, roads and communications lost
• 1/5 of jobs lost
• prison destroyed caused 400 inmates to escape
• lack of sanitation and contaminated water caused 8000 to die from cholera

Question 19

HAITI-short term responses

Answer 19

• communication systems, transport and hospitals all slowed
• country had little heavy lifting equipment so it was hard to look for survivors
• us government sent 3500 soldiers to help
• mass graves made to help with all the bodies

Question 20

HAITI-long term responses

Answer 20

• world bank stopped countries debt for 5 years
• 6 months after, 98% of rubble remained
• in 2014 170,000 people were still in camps
• 70% lacked access to electricity
• 23% of kids didn’t return to primary school

Question 21

BOXING DAY TSUNAMI-2004

Answer 21

• East Indian Ocean 9.0 magnitude earthquake below Indian Ocean caused a 30 m wave
• it affected 12 countries
• the death toll was 300,000
• lack of warning system took people by surprise
• fishing communities lost all local income

RESPONSES:$14 billion was provided in aid
US provided aircrafts for search and rescue
tsunami systems have now been put in place to reduce the effect next time

Question 22

epicentre=

Answer 22

the point of the earths surface, vertically above the focus of the earthquake

Question 23

focus=

Answer 23

inside the earths crust where the earthquake originates from