Question 1: Define seismic waves and explain how they are generated during an earthquake.

Answer: Seismic waves are vibrations that travel through the Earth's crust caused by the sudden release of energy during an earthquake.

Question 2: Name and briefly describe the two main types of seismic waves.

Answer: The two main types are P-waves (primary or longitudinal waves) which are faster and travel through solids and liquids, and S-waves (secondary or transverse waves) which are slower and only travel through solids.

Question 1: A seismic wave travels at a speed of 6 km/s. How long does it take for the wave to travel a distance of 150 km? (Use the formula: time = distance / speed)

Answer: 25 seconds

Question 2: If the P-wave velocity in a particular region is 8 km/s and the S-wave velocity is 4.8 km/s, calculate the ratio of their speeds.

Answer: 1.6667

Question 1: Describe a simple experiment to demonstrate how seismic waves can be detected using a seismometer. Include the key variables involved and safety precautions.

Answer: Students can set up a seismometer using a suspended mass attached to a frame with a recording device. When vibrations occur, the mass remains stationary while the frame moves, causing the recording device to detect the motion. Key variables include the amplitude and frequency of vibrations, and safety precautions involve ensuring the equipment is securely mounted and away from potential impact sources.

Question 2: Identify three variables that affect the speed of seismic waves and explain their influence.

Answer: Variables include the type of material (e.g., rock, sediment), its density, and its elastic properties. Higher density and rigidity generally increase wave speed, while softer materials decrease it.

Question 1: In a seismic event, P-waves are recorded 30 seconds after the initial tremor, while S-waves are recorded 50 seconds after. The distance to the epicentre is 240 km. Calculate the average speeds of P-waves and S-waves in this event.

Answer: P-wave speed = 8 km/s; S-wave speed = 4.8 km/s

Question 2: Based on the data provided, which wave caused more damage and why? Consider their energy and wave properties in your answer.

Answer: S-waves generally cause more damage as they have higher amplitude and cause more ground movement. Although P-waves arrive earlier and are faster, S-waves produce larger displacements, resulting in greater destructive potential.

Question 1: Explain how understanding seismic wave velocities aids in exploring beneath the Earth's surface, such as in oil and mineral exploration.

Answer: By analysing seismic wave velocities, geologists can determine the types and properties of underground materials, helping to identify resource-rich areas and map subsurface structures.

Question 2: Discuss the importance of seismic wave studies in earthquake risk assessment and building design.

Answer: Seismic wave studies enable scientists to locate fault lines and estimate the potential severity of earthquakes. This information is crucial for designing buildings and infrastructure that can withstand seismic forces, reducing damage and saving lives.