Geophysics

Use this for “A reflector lies 600 m down in rock carrying waves at 2,000 m/s. When does its echo reach a geophone 800 m from the shot, and what is the moveout?”

Use this for “A ray in 1,500 m/s sediment meets 4,500 m/s rock at 10°. At what angle does it go on, and what is the critical angle?”

Use this for “An ore body 100 m in radius is 500 kg/m³ denser than its host and centred 200 m down. Find its excess mass, peak anomaly and half-width.”

Use this for “A range stands 3 km high on 35 km of normal crust (2.8 g/cm³ over a 3.3 g/cm³ mantle). How deep is its root, and how thick is the crust under the peak?”

Use this for “A lava flow’s remanent magnetism dips 49.1° below the horizontal. At what latitude did the lava cool?”

Use this for “Crust with a surface heat flow of 62.5 mW/m², a conductivity of 2.5 W/(m·K) and 1 μW/m³ of radiogenic heat is 10 °C at the surface. How hot is it 10 km down?”

Use this for “Seafloor is 50 million years old, with k = 3.3 W/(m·K), κ = 1 mm²/s and a mantle 1,300 K hotter than the sea floor. What heat flow comes out of it?”

Use this for “Ground with a relative permittivity of 9 returns a radar echo 40 ns after the pulse. How deep is the target?”

Use this for “A survey must map a plume of salty groundwater under a field. Which geophysical method suits it best?”