Geography · Year 13 · Hazards and Risk Management · Summer Term

Earthquakes: Causes and Impacts

Focuses on the mechanisms of earthquakes, seismic waves, and their primary and secondary impacts.

• National Curriculum Attainment Targets
• A-Level: Geography - Hazards
• A-Level: Geography - Tectonic Processes

About This Topic

Earthquakes arise from sudden stress release along faults in Earth's crust, often at tectonic plate boundaries. Year 13 students study primary waves (P-waves, compressional and fastest) and secondary waves (S-waves, shear and slower), alongside surface waves that cause most surface damage through rolling motions. They connect these to impacts: primary effects like ground shaking and rupture, secondary ones including tsunamis, landslides, liquefaction, and fires. Factors such as epicentre distance, focal depth, soil type, and building quality determine shaking intensity on the Mercalli scale.

This topic aligns with A-Level hazards and tectonic processes, building skills in spatial analysis and risk evaluation. Students compare global case studies, such as the 2010 Haiti quake versus Japan's 2011 Tohoku event, to assess how preparation and engineering mitigate outcomes. Key questions guide them to explain wave damage variations and evaluate building codes from regions like California and New Zealand.

Active learning benefits this topic by using tangible models to visualise wave propagation and structural failure. When students construct and test buildings on improvised shake tables or map real seismic data collaboratively, they grasp abstract mechanics, refine analytical arguments, and connect theory to human geography.

Key Questions

1. Explain how different types of seismic waves cause varying degrees of damage.
2. Analyze the factors that influence the intensity of an earthquake's ground shaking.
3. Compare the effectiveness of different building codes in mitigating earthquake damage.

Learning Objectives

• Analyze the specific mechanisms by which P-waves, S-waves, and surface waves contribute to earthquake damage.
• Evaluate the influence of focal depth, distance from the epicenter, and local geology on seismic wave intensity.
• Compare the effectiveness of different building construction techniques and materials in resisting seismic forces.
• Synthesize information from case studies to explain variations in earthquake impact and recovery.
• Critique the design and implementation of building codes in seismically active regions.

Before You Start

Plate Tectonics

Why: Understanding plate boundaries and movement is fundamental to explaining the underlying causes of most earthquakes.

Types of Rocks and Their Properties

Why: Knowledge of rock types and their behavior under stress is necessary to comprehend fault formation and seismic wave propagation through the crust.

Key Vocabulary

Seismic Waves	Vibrations that travel through Earth carrying the energy released during an earthquake. They include P-waves, S-waves, and surface waves.
Epicenter	The point on Earth's surface directly above the focus, or origin, of an earthquake. Seismic waves are typically strongest at the epicenter.
Liquefaction	A process where saturated soil or sand loses its strength and stiffness due to earthquake shaking, behaving like a liquid.
Mercalli Intensity Scale	A scale used to measure the intensity of an earthquake's effects at a particular location, based on observed damage and human reactions.
Fault	A fracture or zone of fractures between two blocks of rock, where the blocks have slid past each other. Earthquakes commonly occur along faults.

Watch Out for These Misconceptions

Common Misconception

Earthquake magnitude measures local damage.

What to Teach Instead

Magnitude quantifies total energy released; intensity gauges effects at specific sites via Mercalli scale. Shake table activities let students see how same 'magnitude' yields different outcomes by soil or distance, clarifying the distinction through direct comparison.

Common Misconception

All seismic damage comes from P-waves.

What to Teach Instead

Surface waves cause most destruction due to slower speed and amplification. Slinky demos and video analysis help students observe wave behaviours, correcting overemphasis on fastest waves via peer teaching.

Common Misconception

Earthquakes only occur at plate boundaries.

What to Teach Instead

Intraplate quakes happen too, like in the UK. Case study jigsaws expose students to global examples, prompting map work that reveals diverse settings and builds comprehensive tectonic understanding.

Active Learning Ideas

Pairs Demo: Slinky Seismic Waves

Give each pair a slinky. One student creates quick longitudinal jerks for P-waves and transverse shakes for S-waves. Pairs time wave travel along the slinky and note motion differences. Follow with class discussion on damage links.

25 min·Pairs

Small Groups: Shake Table Building Challenge

Groups build structures using spaghetti, marshmallows, and tape to represent different codes. Shake a tray table at varying intensities. Measure collapse thresholds and redesign for resilience. Record findings in shared tables.

50 min·Small Groups

Whole Class: Earthquake Case Jigsaw

Assign groups one quake (e.g., 1906 San Francisco, 2015 Nepal). Research causes, waves, impacts, responses. Regroup to share via jigsaw, then map patterns on class board.

45 min·Small Groups

Pairs Debate: Building Code Comparisons

Pairs prepare arguments for one code (Japan vs. Turkey). Debate effectiveness using evidence from quakes. Vote and reflect on risk reduction criteria.

30 min·Pairs

Real-World Connections

• Structural engineers in earthquake-prone areas like Tokyo, Japan, and Los Angeles, USA, design buildings using base isolation systems and reinforced concrete to withstand seismic activity.
• Emergency management agencies, such as FEMA in the United States, develop hazard mitigation plans that include public education on earthquake preparedness and response strategies.
• Geologists and seismologists at observatories like the USGS monitor seismic activity in real-time, analyzing wave patterns to understand earthquake origins and predict aftershocks.

Assessment Ideas

Discussion Prompt

Pose the question: 'Given the same magnitude earthquake, why might the damage in a densely populated city built on soft sediment be far greater than in a less populated area on solid rock?' Guide students to discuss wave amplification, liquefaction, and building density.

Quick Check

Provide students with a simplified diagram of seismic wave propagation from a fault. Ask them to label the P-wave, S-wave, and surface waves, and briefly describe the primary motion associated with each and the type of damage each is most likely to cause.

Peer Assessment

Students research a specific earthquake case study (e.g., Christchurch 2011, Mexico City 1985). They then present their findings on the primary and secondary impacts to a small group. Peers use a checklist to assess if the presentation clearly explained the role of seismic waves, local geology, and building codes in the event's outcome.

Frequently Asked Questions

What causes different earthquake damages from seismic waves?

P-waves arrive first but cause little damage; S-waves shake structures vertically; surface waves roll the ground, amplifying destruction near epicentres. Factors like depth and geology modify effects. Students benefit from modelling these in groups to predict outcomes and link to real events like Christchurch 2011.

How do building codes reduce earthquake impacts?

Codes mandate base isolation, flexible materials, and damping systems, as in Japan's standards post-1995 Kobe. California uses shear walls effectively. Comparisons show 50-90% damage reduction in retrofitted areas. Encourage students to evaluate via debates using data from recent quakes.

What active learning strategies work for teaching earthquakes?

Use slinky waves, shake tables with model buildings, and jigsaw case studies for hands-on engagement. These make waves tangible, simulate failures, and promote collaborative analysis of impacts. Students retain more by debating codes and mapping data, turning passive recall into critical evaluation skills.

What factors influence earthquake ground shaking intensity?

Epicentre proximity, focal depth, local geology (soft soils amplify), and structure type control intensity. Mercalli scale rates effects from I (barely felt) to XII (total destruction). Data mapping activities help students quantify these, connecting to preparedness planning in hazard units.