Earthquakes, processes, hazards and their impacts — Eduqas A-Level Geography

Earthquakes are sudden, violent shaking of the ground caused by the release of stress along faults in the Earth's crust. This topic explores the processes that generate earthquakes, including plate tectonics, elastic rebound theory, and the role of fault types (normal, reverse, strike-slip). You'll learn how seismic waves (P, S, surface waves) propagate and cause ground shaking, leading to primary and secondary hazards such as liquefaction, landslides, tsunamis, and fires. Understanding these processes is crucial for predicting impacts and designing mitigation strategies.

The impacts of earthquakes vary greatly depending on magnitude, depth, distance from epicentre, local geology, and human factors like building standards and preparedness. In the WJEC A-Level Geography course, you'll study case studies from developed (e.g., 2011 Christchurch, New Zealand) and developing (e.g., 2010 Haiti) countries to compare vulnerability, resilience, and recovery. This topic links to broader themes of hazard management, risk perception, and sustainable development, helping you understand why some societies suffer more than others.

Mastering earthquakes is essential for understanding plate tectonics as a whole. It connects to volcanic activity, tsunami generation, and the formation of landforms. For your exams, you'll need to evaluate the effectiveness of prediction, protection, and preparedness strategies, and critically assess the role of technology and governance in reducing disaster risk. This knowledge is not just academic—it saves lives in earthquake-prone regions worldwide.

• →Elastic Rebound Theory: Stress builds along a fault until rocks rupture, releasing energy as seismic waves. Understand the cycle of strain accumulation and sudden slip.
• →Seismic Waves: P-waves (compressional, fastest), S-waves (shear, slower, cause most damage), and surface waves (Love and Rayleigh waves, cause rolling motion and greatest destruction).
• →Magnitude vs. Intensity: Magnitude (e.g., Richter, Moment Magnitude) measures energy released; intensity (e.g., Mercalli scale) measures shaking and damage at a location.
• →Primary vs. Secondary Hazards: Primary include ground shaking and surface rupture; secondary include liquefaction (soil behaving like liquid), landslides, tsunamis, and fires.
• →Vulnerability and Resilience: Factors like building design, population density, education, and wealth determine a community's ability to withstand and recover from earthquakes.

• Earthquake characteristics including P and S waves, focus, depth, and epicentre.
• Earthquake processes and associated hazards: ground shaking, liquefaction, landslides, and tsunami.
• Environmental, demographic, economic, and social impacts (primary and secondary effects).
• Impacts at local, regional, and global scales.
• Use of examples in contrasting contexts to demonstrate varied risk and impacts.
• Human factors affecting risk: economic (development/technology), social (density/profile/education), political (governance), and geographical (location/isolation).
• Responses: monitoring, prediction, warnings, mitigation (modifying event, vulnerability, loss), and the hazard management cycle.

• 💡Ensure examples are contemporary (within the last two decades).
• 💡Explicitly link tectonic processes to the resulting hazards.
• 💡Use the hazard management cycle to structure responses regarding mitigation and response.
• 💡When discussing risk, always consider the interaction between physical hazard and human vulnerability.
• 💡Use specific terminology such as 'liquefaction' and 'P and S waves' accurately.
• 💡Use specific case study details (dates, magnitudes, death tolls, economic costs) to support your answers. For example, compare the 2010 Haiti earthquake (Mw 7.0, 200,000+ deaths) with the 2011 Christchurch earthquake (Mw 6.3, 185 deaths) to illustrate how development level affects impacts.
• 💡Always link physical processes to human impacts. Don't just describe how an earthquake occurs—explain why certain areas are more vulnerable (e.g., poor building codes, high population density, lack of early warning systems).
• 💡Evaluate management strategies critically. For instance, while Japan's early warning system is effective, it cannot prevent all damage; discuss limitations like cost, false alarms, and public complacency.

• Confusing primary and secondary hazards or effects.
• Failing to use contrasting contexts for examples.
• Neglecting the distinction between hazard and disaster.
• Over-focusing on the event itself rather than the human factors influencing vulnerability.
• Inadequate application of the hazard management cycle.
• Misconception: Earthquakes only occur at plate boundaries. Correction: While most occur at boundaries, intraplate earthquakes (e.g., 1811 New Madrid, USA) happen within plates due to ancient faults or stress from plate movements.
• Misconception: The Richter scale is still the standard for measuring all earthquakes. Correction: The Moment Magnitude scale (Mw) is now preferred for large earthquakes as it more accurately measures total energy release; Richter is only accurate for small, local quakes.
• Misconception: Tsunamis are caused by all undersea earthquakes. Correction: Only earthquakes that cause vertical displacement of the seafloor (e.g., subduction zone megathrusts) generate tsunamis; strike-slip quakes rarely do.