# Explain how seismic waves produced by earthquakes provide evidence for the internal structure of the Earth, including the existence of a liquid outer core.

> Eduqas A-Level Physics — 5.2 Gravitational fields (A-Level only) · Explain · 5 marks

> When an earthquake occurs, seismic waves travel through the Earth and are detected at monitoring stations around the world. Scientists have used the patterns of wave detection to draw conclusions about the layers inside the Earth.

## Mark scheme (5 marks)

1. P-waves are longitudinal seismic waves that can travel through all mediums (solids and fluids)
2. S-waves are transverse seismic waves that cannot travel through fluids/liquids
3. S-waves are not detected on the opposite side of the Earth from the earthquake, creating a 'shadow zone'
4. This shows that part of the Earth's interior must be liquid, since S-waves cannot pass through fluids
5. P-waves are still detected on the far side of the Earth, confirming that a solid inner core exists through which they can travel

## Key terms

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

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-seismic-waves-produced-by-3cb05a84) · Published by Druglandscape Ltd.