By studying seismographs, scientists can analyze the depth of the Earth's layers.
Analyzing the depth of the Earth's layers:
The geologists can know about the deep layers of the Earth's crust by examining the seismic waves collected through seismographs, which travels through the Earth when an earthquake takes place. By observing the time of the arrival of the prime set of waves, and how the arrangement of the frequencies of the waves is there within the set, scientists can know about the density and other features of the layers.
The comparative differences in the arrival times of the S and P seismic waves at different recording stations assist geologists to know the different speeds by which waves are travelling, this further assists in knowing the density of the material the layer is formed of, and the thickness of the layer in distinct directions.
Thus, the correct answer is option a, that is, the depth of the Earth's layers.
Find out more information about study of the Earth's interior here:
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