EARTH SCIENCE
EARTHQUAKES
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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P-waves arrive earlier than S-waves.
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P-waves and S-waves are both recorded at all stations.
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Only S-waves are recorded at all stations.
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Only P-waves are recorded on the opposite side of Earth.
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Detailed explanation-1: -Which evidence recorded at seismic stations following an earthquake supports the inference that Earth’s interior changes from solid rock to molten iron and nickel at the mantle-core boundary? P-waves arrive earlier than S-waves.
Detailed explanation-2: -Knowing how the waves behave as they move through different materials enables us to learn about the layers that make up the Earth. Seismic waves tell us that the Earth’s interior consists of a series of concentric shells, with a thin outer crust, a mantle, a liquid outer core, and a solid inner core.
Detailed explanation-3: -When P-waves strike the outer core, however, they bend downward when traveling through the outer core and bend again when they leave. This indicates that P-waves slow down in the outer core, suggesting that this layer has a significantly different composition from the mantle and may actually be liquid.
Detailed explanation-4: -Because the speed of the seismic waves depends on density, we can use the travel-time of seismic waves to map change in density with depth, and show that the Earth is composed of several layers.
Detailed explanation-5: -Seismic waves move faster through denser or more rigid material. As P-waves encounter the liquid outer core, which is less rigid than the mantle, they slow down. This makes the P-waves arrive later and further away than would be expected. The result is a P-wave shadow zone.