Question 1: Seismic waves are vibrations that travel through the Earth's interior or along its surface, typically caused by earthquakes or other underground disturbances. They are classified into body waves and surface waves, each with different properties.

Answer: Seismic waves are vibrations that travel through the Earth, caused by earthquakes; they include body and surface waves.

Question 1: Define 'P-waves' and describe how they differ from 'S-waves' in terms of movement and speed.

Answer: P-waves are primary or compressional waves that travel fastest and move through solids and liquids; S-waves are secondary or shear waves that are slower and move only through solids.

Question 2: Explain why seismic waves are important for understanding Earth's internal structure.

Answer: Because seismic waves change speed and direction when passing through different materials, studying them reveals the composition and layers inside the Earth.

Question 1: Calculate the speed of a P-wave if it travels 3000 km in 20 minutes. Use the formula: Speed = Distance / Time. (Convert time to seconds).

Answer: Speed = (3000 km) / (20 min × 60 s) = 3000 km / 1200 s = 2.5 km/s

Question 2: A surface wave travels at 3 km/s and is recorded to have taken 10 seconds to pass a seismic station. How far did the wave travel?

Answer: Distance = Speed × Time = 3 km/s × 10 s = 30 km

Question 1: Describe a simple theoretical experiment to demonstrate how seismic waves can be detected and measured in a laboratory setting.

Answer: Use a shaker to generate vibrations on a medium like gel or sand, and measure the wave speed with sensors at different distances, ensuring safety by avoiding excessive vibration.

Question 2: Identify two variables that need to be controlled in a seismic wave experiment and explain why.

Answer: Variables include the amplitude of vibrations and the type of medium, to ensure consistent wave speed measurements and valid comparisons.

Question 1: A seismic event produces P-waves travelling at 8 km/s and S-waves at 4.5 km/s. What can you infer about the Earth's internal layers based on these speeds?

Answer: The higher speed of P-waves indicates they travel through denser, possibly liquid or solid layers, while S-waves' slower speed suggests they are limited to solid layers, revealing information about Earth's composition.

Question 2: If the difference in arrival times of P-waves and S-waves at a seismic station is used to estimate the distance to the earthquake epicentre, explain the principle behind this method.

Answer: The method relies on the fact that P-waves arrive first due to their higher speed. By measuring the time difference between P and S wave arrivals and knowing their speeds, the distance to the epicentre can be calculated using the difference in travel times.

Question 1: Explain how seismic wave analysis helps in assessing earthquake risks and in designing earthquake-resistant structures.

Answer: Seismic analysis reveals how seismic waves travel and their intensity, helping engineers design buildings that can withstand shaking and enabling authorities to assess earthquake hazards.

Question 2: Describe how seismic wave data can be used in the oil and gas industry.

Answer: Seismic survey data is used to map underground rock layers and identify potential oil and gas reservoirs by analysing how seismic waves reflect and refract within Earth's subsurface.