# Explain why seismologists can use seismic waves to determine the internal structure of the Earth.

> WJEC GCSE Physics (Wales) — 1.7 Seismic waves · Explain · 4 marks

> When an earthquake occurs, seismic waves travel through the Earth and are detected at seismic stations around the world. Scientists study the patterns of wave arrivals to learn about the Earth's interior.

## Mark scheme (4 marks)

1. There are two types of seismic wave: P-waves (longitudinal) and S-waves (transverse)
2. S-waves cannot travel through liquids (they are blocked/absorbed by the liquid outer core)
3. Both P-waves and S-waves change speed and change direction (refract) when they pass from one layer into another
4. The pattern of detected waves (shadow zones / which stations receive which waves) reveals the nature and depth of the Earth's internal layers

## Key terms

- [seismic waves](https://www.gradenine.co.uk/glossary/seismic-waves)

## Related

- [Revision notes for WJEC GCSE Physics (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-seismologists-can-use-seismic-f5f3cbe4) · Published by Druglandscape Ltd.