Earthquakes Flashcards
Where do earthquakes occur?
Nearly all earthquakes occur at plate boundaries.
Where is one of the most deadly subduction zones located?
The subduction zone off the coast of Japan.
What is happening at the Japan Subduction zone?
The heavier Pacific Plate is being dragged under the Eurasian Plate.
How many earthquakes hit Japan every year?
About 1,500
What is Disaster Prevention Day?
This takes place on the Anniversary of the Great Kanto Earthquake of 1923 which killed 100,000 people.
Disaster preparations are taken nationwide. (1st of September)
Where do the most common and intense earthquakes occur at?
At subduction zones at convergent boundaries.
Give an example of a recent earthquake that occurred at a subduction zone.
The Japan Earthquake of 2011.
Due to the focus being under the ocean, a tsunami occurred also.
Apart from Japan, where else are earthquakes common?
Along the boundary between China and India.
Here two continental plates (the Indo-Australian and Eurasian) collide resulting in the formation of the Himalayas.
Why are the earthquakes that occur in China and India dangerous?
While they are not as powerful as those at subduction zones:
The relatively shallow depth of the focus means that the seismic waves do not have as far to travel.
They can cause a lot of damage to the surface.
Give an example of an earthquake that occurred in Nepal.
The Nepal Earthquake of 2015
Killed 8,000 people
Damaged 130,000 buildings
Deadliest day on Everest- 22 people were killed.
The Indian plate is converging on the Eurasian plate at a rate of 5 cm per year
Give an example of an earthquake in China.
The Sichuan Earthquake of 2008
Killed 69,000 people
5 million homeless.
What other plate boundary do earthquakes occur at?
America
Passive/Transform boundaries.
Name a passive/transform boundary.
The San Andreas Fault in California
What are seismic waves?
The energy released from an earthquake
What are foreshocks?
A major earthquake may be proceeded by smaller earthquakes
What are aftershocks?
Smaller earthquakes that follow after a major earthquake
What is the epicenter?
The point on the surface directly above the focus, where tremors are the strongest and the worst damage occurs
What is the focus?
The point deep in the Earth’s crust where the earthquake originates. If the focus is under the sea a tsunami will occur
What factors can help geologists predict earthquakes?
- Measuring rock stress
- Measuring radon gas emissions
- Changes in water and oil levels
- Unusual animal behaviour
- Seismic Gaps
- Early warning systems
What factors affect the damage caused by an earthquake?
- Economic development
- Population density
- Time of day
- Rock type
- Depth of focus
- Energy and duration
Name the impacts of earthquakes
- Soil liquefaction
- Fire and service disruption
- Falling debris
- Tsunamis
How do you reduce the effects of an earthquake?
- Earthquake drills
- Efficient urban planning
- Early warning systems
- Earthquake proof buildings/infrastructure
Name the two ways to measure an earthquake
- The Richter Scale
- The Mercalli Scale
What does the Richter Scale measure?
Measures the intensity or magnitude of an earthquake/measures the energy released by an earthquake.
Named after Charles Richter
What does the Mercalli scale measure?
- Does not use instruments
- Describes the effects or intensity of an earthquake based on human observations
- Scale runs from 1 - 12
