Earthquakes Flashcards
What are most earthquakes caused by?
Movement on plate tectonic boundaries, remaining earthquakes are caused by volcanoes/magma movement
What causes stress along the lithosphere?
Friction
What do rocks under stress do? What are they called?
Fracture along cracks - called faults
What is the focus or hypocentre of an earthquake?
The breaking point
What is the epicentre?
The point on the surface directly above the focus and usually experiences the most violent ground shaking
How long does the main earthquake tremor last?
Less than a minute but several aftershocks
What is the former earthquake scale?
Richter scale
What is wrong with the Richter scale?
Objective and is a measurement of magnitude
What is the current earthquake scale?
Mercalli
What is the Mercalli scale?
Measures intensity - damage released
What is a problem with the Mercalli scale?
Subjective - depends on observer
What are the 2 primary earthquake hazards?
Ground rupture
Ground shaking
What are the 4 secondary earthquake hazards?
Liquefaction
Fires
Landslides
Tsunamis
What can ground shaking be like?
Can cause lateral movement which can damage buildings
What are 2 impacts of ground shaking?
Weak buildings collapsing
Walls and floors become separated leading to pancaking
What is pancaking?
Floors collapse on top of each other
What is ground rupture?
The visible breaking and displacement of the Earth’s surface
What is liquefaction?
Ground that is water logged will separate into soil/sand and water which will rise to the top
What is the problem with liquefaction?
Can lead to mudflows which can submerge buildings
Why can fire occur?
From ruptured gas mains
How can landslides occur?
Caused by slope failure as a result of an earthquake e.g 4312 landslides Nepal 2015
What are 2 preparation methods of predicting earthquakes?
Foreshocks
Ground deformation
How can you mitigate an earthquake?
Hazard resistant designs
Steel due to it being flexible and ductile
How can mass dampers reduce the movement of buildings?
Can improve resistance of buildings
How can cross-bracing be used for quakes?
Strength added to floors and walls to stop pancaking
How can people adapt for earthquakes?
Identify high-risk areas
Putting critical buildings e.g schools in low-risk areas
