Hazards - Seismic Flashcards
(29 cards)
How can scientists predict earthqaukes? (2)
1 - Measure changes in the shape of the earthquake
2 - Monitor tiny earthquakes
What are the primary effects?
Effects that are a direct result of the hazard
What are secondary effects?
Impacts that are caused by primary impacts
What are the social impacts of seismc hazards? (3)
1 - Building damage - homelessness
2 - Rupture gas pipes and break power lines leading to fires
3 - Tsunamis flood large areas - destroy crops, kill people
What are the environmental impacts of seismic hazards? (3)
1 - Damaged power plants leak toxic chemicals
2 - Fires
3 - Water salinised by tsunamis
What are the political impacts of seismic hazards? (3)
1 - Lack of food and water cancause conflict and unrest
2 - Countries development stunted as money put aside to spend on development was spent on repairing damage
3 - Money may need to be borrowed putting causing debt
What are the economic impacts of seismic hazards? (3)
1 - Ground shaking and liquedaction destroy shops
2 - Damage to industry could lead to country relting on expensive imports of goods
3 - Damage expensive to repair
What is liquefaction?
Ground shakes so much that it becomes soft
How can the effecyts of seismic hazards be prevented? (2)
1 - Prevent land that is prone to liquefaction being built on
2 - Build sea walls to prevent tsuamis hitting land
How can the effects of a seismic hazard be prepared against? (4)
1 - Earthquake warning systems via TV, radio
2 - Staying away from buildings, using desk as shelter
3 - Evacuation routes signposted
4 - Search and rescue teams + Fire response units
How can people adapt to mitigate againts seismic risks? (2)
1 - Buidlings designed to sway rather than break by using flexible materials
2 - Tall and strong buildings protect from tsunamis
How many deaths have been attributed to stroms in the last 200 years?
1.9 mil - 10,000 per year
What are the two types of Body waves?
1 - Primary 2 - Secondary
What are the two types of surface waves?
1 - L waves 2 - R waves
Describe the process of an earthquake? (5)
1 - 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 the earths surface directly above the focus so is where the earthquake is felt first
5 - Eathquakes cause the ground to shake and rupture
What are the three scales which are used to measure an earthquake? (3)
1 - Richter scale - measures the magnitude
2 - Moment magnitude scale (MMS) - Measures energy released by an earthuquake
3 - Mercalli scale - Measures the impacts of an earthquake
Which scale is more accurate, Richter or MMS?
MMS so is more widely used
Descirbe the process of a tsunami? (2)
1 - An underwater earthquake causes the sea bed to move which displaces large volumes of water
2 - The greater the movement of the sea bed the more water displaced and the bigger the wave from the epicentre
What are the features of a tsunami? (2)
1 - Tsuanmis that start near the coast are more powerful because the waves lose less energy as they travel towards land
2 - The waves travel very fast so hit the shore with little warning - high death toll
How are Avalances and Landslides caused? (2)
1 - Shaking of the ground dislodges rock/soil/snow which can cause landslide or avalanches which quickly move downslope
2 - The shaking can lossen ground material which means more water infiltrates. The extra water weight can cause a landslide even after the earthquake has stopped
How does soil liquefaction occur? (2)
1 - When soil is saturated with water the vibrations of an eathquake can cause it to act like fluid
2 - This makes the soil weaker and easier to deform. This makes it more likely to collapse where it has a heavy wight on top of it
How does margin type affect an earthquake? (2)
1 - Earthquakes at destructive plate margins have a higher magnitude than earthquakes at constructive plate margins
2 - This is because the subduction of the plate at a destructive margin causes lots of pressure to build up leading to a huge erathquake when this is released
How does the depth of the focus affect an earthquake? (2)
1 - Deep focus earthquakes have higher magnitudes than shallow focus earthquakes
2 - Deep focus earthquakes however cause less damage that shallow earthquakes because the shock waves have to travel further to reach the surface which reduces their power
Do seismic hazards follow a pattern?
No they are random
