Seismic Waves & Earth's Interior

Question 1

Which statement best explains why a seismograph on the opposite side of the Earth from an earthquake does NOT record any S‑waves?

Accepted Answer

S‑waves cannot travel through liquids, and the liquid outer core blocks them from reaching the far side of the Earth.

Answer

S‑waves travel more slowly than P‑waves and arrive after the seismograph has been turned off.

Answer

S‑waves are absorbed by the solid mantle, so they die out before they can get to the far side.

Answer

The Earth's magnetic field deflects S‑waves away from the far side of the planet.

Question 2

An earthquake occurs beneath the island of Lumen. The seismometer in the town of Vale, which lies almost directly on the opposite side of the Earth from Lumen, records only P‑waves and no S‑waves. Which paragraph best explains why the Vale station does not detect any S‑waves?

Accepted Answer

S‑waves are shear waves that require solid material to move. When they reach the liquid outer core, they cannot travel through it, so they are stopped and never reach the far side of the Earth, creating a seismic shadow zone.

Answer

S‑waves travel more slowly than P‑waves, so they arrive after the seismometer has stopped recording; only the faster P‑waves are captured.

Answer

The Earth’s magnetic field blocks S‑waves on the far side, allowing only P‑waves, which are not affected by magnetism, to be recorded.

Answer

S‑waves are weaker than P‑waves, and by the time they travel halfway around the Earth they lose so much energy that the seismometer cannot detect them.

Question 3

A magnitude 6.2 earthquake occurs beneath the island of Kestrel. The seismograph in the town of Nadir, which is situated on the other side of the planet from the quake’s epicenter, records only the fast shaking (P‑waves) and shows no sign of the slower side‑to‑side shaking (S‑waves). Which paragraph best explains why the seismograph at Nadir did not record any S‑waves?

Accepted Answer

S‑waves are shear waves that cannot travel through liquids. When they reach Earth’s liquid outer core, they are stopped, so they never reach the far side where Nadir is located. P‑waves, which can move through both solid and liquid layers, are the only waves that arrive.

Answer

The Earth’s magnetic field blocks the side‑to‑side motion of S‑waves, preventing them from reaching locations on the opposite side of the planet.

Answer

S‑waves travel more slowly than P‑waves, so they arrive later and the seismograph was turned off before they could be recorded.

Answer

The crust beneath Nadir is unusually thick, which absorbs the S‑waves before they can be detected.

Try three questions

Which statement best explains why a seismograph on the opposite side of the Earth from an earthquake does NOT record any S‑waves?

An earthquake occurs beneath the island of Lumen. The seismometer in the town of Vale, which lies almost directly on the opposite side of the Earth from Lumen, records only P‑waves and no S‑waves. Which paragraph best explains why the Vale station does not detect any S‑waves?

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