Seismic hazard

Question 1

Relation between seismicity and earthquakes

Answer 1

Earthquakes are primry hazard of SA

Question 2

Describe formation earthquake

Answer 2

• Plates jerk past eachother which builds up pressure

2 - When this pressure is released it sends out shockwaves which are the earthquake

3 - The shockwaves spread out from the focus. The nearer the focus the waves are stronger and cause more damage

4 - The epicentre is where the eqrtahuke is felt first on earths surface , above the focus

Question 3

Formation tsunamis

Answer 3

• tsuamis = large waves caused by dispalcment lare vol water
• An underwater earthquake causes the sea bed to move which displaces large volumes of water
• waves rdiate from epricnetre

2 - The greater the movement of the sea bed the more water displaced and the bigger the wave

• more powrful close to coast as waves lost less E - fast therefore little warning

Question 4

Formation Landslides and Avalabches

Answer 4

1 - Shaking gorund – rock/ snow dislocfe and moves downslope quickly – A or L
2 - loosening material - more ifiltartion - weight of water – landslide

Question 5

Soil liqeuefaction?

Answer 5

1 - soil safy water
2 - vibrations earthquke cause soil to act like fluid
3 - therefore soil waker –> increased liklihood it subsidicng - in oartciaukr when buikding on top

Question 6

Factors affecting mag or earthauke?

Answer 6

Margin type:

• highest mag at detsrucvive
• bcause subcution plate caused bugger build up of ppressure

Depth of focus:
- deep focus - higher meg but less dmage because shpck waves have to travel fuethe to recah surface therfeore ;less power

Question 7

Rnaodmness, freucney, peictibilyt?

Answer 7

1 - Random
2 - low mag - high freq vic versa
3 - monuto ovemnet tetconic plates - can;t predistc magnitude or when it will strike

Question 8

Secodnary impacts vs priamry?

Answer 8

pruamty:

• Avalanches
• soil liqyescation
• tasnuamus

Secondary:

• gas pipe leakes –> fires

Question 9

Political imapctr:

Answer 9

• shortage food - soaicl unrest

- borrow monye - debt - stnunt groiwth

Question 10

short term + long term esponise:

Answer 10

ST 
- evcuating 
- rescues - aid 
LT 
- Prevention: 
- Can't but can mitigate against risk - prventbuilding land prone liqefctaon , sea walls tusmas 

• prepradness:
• warnign ustems detct small seicmi waves
• evacuation routes
• search and rescue teams
• Adaptation:
• buildinsg withstand earthquakes - flexbile materila s
• withstand tsauis - tall, riased on foundations