Geology · Year 12 · Earth Structure and Global Tectonics · 1.º Período

Earthquakes and Seismic Waves

Explore the generation and propagation of P, S, and surface waves during seismic events. Students will learn how seismograms are used to locate epicentres and determine earthquake magnitude.

TL;DR:This topic focuses on the mechanics of earthquakes and the diagnostic power of seismic waves. Students learn to distinguish between body waves (P and S) and surface waves (L and R), understanding how their different properties allow geologists to probe the Earth's interior and locate seismic events. This is a core component of the Eduqas AS/A-level Geology curriculum, bridging the gap between physics and earth science.

• National Curriculum Attainment Targets
• Eduqas Geology AS/A-level: 1.3a Seismic waves
• Eduqas Geology AS/A-level: 1.3b Earthquake measurement and hazards

About This Topic

This topic focuses on the mechanics of earthquakes and the diagnostic power of seismic waves. Students learn to distinguish between body waves (P and S) and surface waves (L and R), understanding how their different properties allow geologists to probe the Earth's interior and locate seismic events. This is a core component of the Eduqas AS/A-level Geology curriculum, bridging the gap between physics and earth science.

Students will move from the theoretical understanding of wave propagation to the practical application of seismogram analysis. They will learn to calculate the distance to an epicentre using P-S arrival times and understand the logarithmic nature of the Richter scale versus the qualitative Mercalli scale. This quantitative work is vital for developing the mathematical skills required in the A-level specification.

This topic particularly benefits from hands-on, student-centered approaches where students can manipulate real seismic data and simulate wave motion to see the physical differences in particle displacement.

Key Questions

1. How do P-waves and S-waves travel through the Earth?
2. How is the epicentre of an earthquake located?
3. What factors influence earthquake magnitude and intensity?

Watch Out for These Misconceptions

Common Misconception

The epicentre and the focus are the same thing.

What to Teach Instead

The focus (hypocentre) is the actual point of rupture underground, while the epicentre is the point directly above it on the surface. Drawing 3D diagrams in small groups helps students visualise this vertical relationship.

Common Misconception

A magnitude 7 earthquake is only slightly stronger than a magnitude 6.

What to Teach Instead

Because the Richter scale is logarithmic, a magnitude 7 releases about 32 times more energy than a magnitude 6. Using a visual 'energy bucket' comparison helps students grasp the massive scale of these differences.

Active Learning Ideas

Inquiry Circle

Locating the Epicentre

Students are given seismograms from three different stations. They must calculate the P-S time interval, use a travel-time graph to find the distance, and use compasses to triangulate the epicentre on a map.

45 min·Small Groups

Think-Pair-Share

Magnitude vs Intensity

Students are given a scenario of an earthquake hitting two different cities. They must discuss why the magnitude is the same for both but the intensity (Mercalli) differs, then share their factors (building design, rock type) with the class.

20 min·Pairs

Simulation Game

Human Seismic Waves

Students stand in a line. To model P-waves, they push the shoulder of the person in front (compression). To model S-waves, they move their arms up and down (transverse). This physically demonstrates why S-waves cannot pass through liquids.

15 min·Whole Class

Frequently Asked Questions

What is the difference between P-waves and S-waves?

P-waves (Primary) are longitudinal waves that compress and expand the ground; they are the fastest and can travel through solids and liquids. S-waves (Secondary) are transverse waves that move the ground up and down or side to side; they are slower and can only travel through solids.

How is the Richter scale calculated?

The Richter scale measures the amplitude of the largest seismic wave recorded on a seismograph. It is a logarithmic scale, meaning each whole number increase represents a tenfold increase in measured amplitude and roughly 32 times more energy release.

What are the best hands-on strategies for teaching earthquakes?

Triangulation exercises are the gold standard. Providing students with raw seismograph data and requiring them to use compasses and travel-time curves to find an epicentre mimics real-world geophysics. Using 'Slinky' springs to model wave types also provides a tactile way to understand compression versus shear motion.

Why do surface waves cause the most damage?

Surface waves (Love and Rayleigh waves) travel more slowly than body waves but have much larger amplitudes. They create complex horizontal and vertical ground movement, which is particularly destructive to building foundations and infrastructure.