What Seismic Waves Tell Us About Earth's Structure
Part of Seismic Waves — GCSE Physics
This key facts covers What Seismic Waves Tell Us About Earth's Structure within Seismic Waves for GCSE Physics. Revise Seismic Waves in Waves for GCSE Physics with 13 exam-style questions and 15 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 5 of 14 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 5 of 14
Practice
13 questions
Recall
15 flashcards
🌍 What Seismic Waves Tell Us About Earth's Structure
Key evidence:
- S-wave shadow zone: S-waves don't arrive on the opposite side of Earth from an earthquake — there is a large shadow zone
- This proves there's a liquid layer (outer core) that S-waves cannot pass through
- P-wave shadow zone: P-waves are refracted (bent) by the core, creating a partial shadow zone between about 105° and 140° from the earthquake
- Refraction occurs because the core has a different density from the mantle, causing waves to change speed and direction
- Solid inner core: Some P-waves are detected arriving through the very centre, and their travel times suggest a solid inner core
Quick Check: Why do S-waves not reach the other side of Earth from an earthquake?
S-waves are transverse waves that can only travel through solids. Earth's outer core is liquid, and S-waves cannot pass through a liquid (liquids cannot support shear forces). When S-waves hit the liquid outer core, they are absorbed and cannot travel any further, creating an S-wave shadow zone on the far side.