Seismic Waves and Measurement Questions and Answers

Answer: A

Correct answer: time

An accelerogram is a time history: the acceleration of the ground plotted against time, usually for each of three components. Everything else follows from it - the peak value by inspection, the duration of strong shaking by its envelope, the velocity and displacement by integration, and the response spectrum by running the record through a series of single-degree-of-freedom oscillators.

Answer: B

Correct answer: carry information from depths no drill can reach

The deepest borehole ever drilled reaches about 12 km, a fraction of one per cent of the earth’s radius, whereas seismic waves pass through the entire planet and return with their travel times and amplitudes altered by everything they met. Almost all we know of the mantle and the core - the depth of the Moho, the transition zones, the liquid outer core, the solid inner core - comes from reading those changes.

Answer: C

Correct answer: S wave

The S wave is a body wave, travelling through the interior of the earth. Rayleigh and Love waves are the two surface waves, and ground roll is the name given to the Rayleigh wave when it appears as unwanted noise on a shallow seismic survey. Surface waves are confined near the surface and attenuate slowly with distance, which is why they dominate the later part of a distant seismogram.