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The diagram shows part of the boundary between two tectonic plates - Edexcel - GCSE Physics - Question 4 - 2013 - Paper 1
Question 4
The diagram shows part of the boundary between two tectonic plates. (i) Complete this sentence by putting a cross (✔) in the box next to your answer. The plates ar... show full transcript
Worked Solution & Example Answer:The diagram shows part of the boundary between two tectonic plates - Edexcel - GCSE Physics - Question 4 - 2013 - Paper 1
Step 1
Step 2
Describe what happens at the plate boundary to cause this earthquake.
Answer
At the plate boundary, the tectonic plates are in constant motion due to convection currents in the mantle. When plates slide past each other, they can become locked due to friction. Eventually, the stress exceeds the frictional force, causing an abrupt release of energy, which results in an earthquake. This release of energy produces seismic waves that travel outward from the epicentre.
Step 3
Show that it takes about 2 minutes for the S waves from the earthquake to reach the seismometer.
Answer
To calculate the time it takes for the S waves to reach the seismometer, we can use the formula:
t = rac{d}{v}
where:
- t is the time,
- d is the distance (80 km),
- v is the speed of the S waves (0.65 km/s).
Plugging in the values:
t = rac{80}{0.65} ext{ s} \n
Calculating this gives approximately 123.08 seconds, which is about 2.05 minutes.
Step 4
Describe how scientists can use seismometer records of P and S waves to locate the epicentre.
Answer
Scientists analyze the seismometer records by identifying the arrival times of both the P waves and S waves. P waves arrive first because they travel faster (approximately 10 times faster than S waves). By measuring the time difference between the arrivals of the two waves at multiple seismometer locations, scientists can calculate the distance of the seismic station from the epicentre. Using data from at least three seismometer stations, they can triangulate the precise location of the epicentre.
Step 5
Suggest an explanation for this.
Answer
Some animals can detect frequencies below the human hearing range, such as infrasound, which may allow them to sense the seismic waves generated by an earthquake. Additionally, certain animals may have heightened tactile sensitivity, enabling them to feel the ground's vibrations before humans become aware of them.