HAZARDS - earthquakes

Question 1

where do earthquakes occur?

Answer 1

closely related to location of plate boundaries.

Question 2

nature of earthquake at constructive boundaries

Answer 2

shallow focus

mid ocean ridge = low hazard

Question 3

nature of earthquake at collision boundaries

Answer 3

shallow focus

fold mountain formation

Question 4

nature of earthquake at destructive boundaries

Answer 4

deeper focus in the benioff zone due to compressional forces

Question 5

nature of earthquake at conservative plate boundaries

Answer 5

shallow focus

Question 6

what percentage of earthquakes are intraplate?

Answer 6

10%

Question 7

focus

Answer 7

point at which the pressure was released within the crust

Question 8

epicentre

Answer 8

point at the surface, directly above the focus. where the most intense shaking occurs.

Question 9

seismic wave

Answer 9

shockwaves that radiate from the focus.

Question 10

what are the two types of seismic waves?

Answer 10

body waves and surface waves

Question 11

body waves

Answer 11

travel through the earth

there are primary and secondary body waves

Question 12

primary waves

Answer 12

LONGITUDE waves
high frequency
FASTEST of the body waves
travels through SOLIDS and LIQUIDS

Question 13

secondary waves

Answer 13

TRANSVERSE waves
high frequency
half the speed of p waves - SLOW
travels through SOLID only

Question 14

what type of movement do P and S waves cause

Answer 14

P = back and forth = ground cracks
S = shaking up and down

Question 15

surface waves

Answer 15

travel along the earths surface = larger hazard

Question 16

love waves

Answer 16

type of surface wave = shakes ground at 90* to the direction of movement
slower = more damage
damages infrastructure and buildings

Question 17

Rayleigh waves

Answer 17

type of surface wave
rolling motion
radiates from epicentre in complex low frequency motion
breaks surface

Question 18

liquefaction

Answer 18

secondary impact of earthquakes

unconsolidated sediment is saturated with water and acts like liquid due to the shaking

Question 19

effect of liquefaction

Answer 19

subsidence of building foundation

destruction of utility pipes

Question 20

landslides

Answer 20

unstable material on slopes fall due to ground shaking

Question 21

effects of landslides

Answer 21

injuries, blocked path, emergency aid unable to pass

Question 22

Tsunamis

Answer 22

effect of earthquakes
large waved formed due to subduction of plate offshore
over 10m high
coastal flooding and destruction

Question 23

what are the three scales earthquakes can be measured in?

Answer 23

mercalli scale
Richter scale
moment magnitude scale

Question 24

mercalli scale

Answer 24

I - XII
based on observations
I = not felt only detected by instruments
XII = total destruction

Question 25

richter scale

Answer 25

1-8
logarithmic scale
amplitude of wave and distance from focus
use a seismometer

Question 26

moment magnitude scale

Answer 26

logarithmic scale with no upper limit
more accurate than the richter scale
measure the total moment released- distance fault moved and forced require to move it (energy)
no upper limit

Question 27

short term impacts

Answer 27

death
injury
destroyed infrastructure and buildings
burst pipes
fires

Question 28

long term impacts

Answer 28

• infrastructure problems
• disruption to supply lines and economy
• 2/3 of Haiti’’s working in agriculture and industry were unemployed
• looting

Question 29

nature of an earthquake is affected by 3 main factors

Answer 29

margin type, rate of movement, depth of focus.

Question 30

compare deep focus and shallow focus earthquakes

Answer 30

shallow = lower magnitude
deep = higher magnitude
shallow = more damage
deep = less damage

Question 31

relationship between frequency and magnitude of earthquakes

Answer 31

high frequency earthquakes tend to have low mag.

high magnitude earthquakes happen less frequently.

Question 32

regularity of earthquakes

Answer 32

don’t follow any pattern

frequency is not an indicator

Question 33

predictability of earthquakes

Answer 33

scientist can monitor tectonic movement and and predict areas at risk
imposible to predict a time and magnitude

Question 34

preparation and mitigation strategies

Answer 34

educate - drills
emergency response
earthquake proof buildings

Question 35

how to make a house earthquake proof

Answer 35

strengthened corners

shock absorbance