Seismic refraction surveys measure travel times of seismic waves along a velocity contrast. Which statement best describes its main application?

Seismic refraction surveys measure travel times of seismic waves along a velocity contrast. Which statement best describes its main application?

• A. Measures travel times along velocity contrasts
• B. Determines rock color and texture
• C. Maps magnetic anomalies
• D. Calculates porosity from waveform amplitude

Answer: (A)

Seismic refraction uses how seismic waves travel across interfaces where velocity changes to reveal the subsurface layering and the depths of those boundaries. When waves strike a boundary with higher velocity, they refract and travel along that boundary, producing first-arrival times that increase in a predictable, linear way with distance in each layer. By plotting travel time versus distance, you get straight-line segments; the slopes give the velocities of the layers, and the intercepts give the depths to the boundaries. This makes the method especially useful for mapping the arrangement of subsurface layers and estimating how deep bedrock or other key interfaces are. The other options don’t fit because rock color and texture aren’t determined from refraction travel times, magnetic anomalies require a magnetic survey, and porosity from waveform amplitude involves different seismic attributes beyond simple refraction time analysis.

Seismic refraction uses how seismic waves travel across interfaces where velocity changes to reveal the subsurface layering and the depths of those boundaries. When waves strike a boundary with higher velocity, they refract and travel along that boundary, producing first-arrival times that increase in a predictable, linear way with distance in each layer. By plotting travel time versus distance, you get straight-line segments; the slopes give the velocities of the layers, and the intercepts give the depths to the boundaries. This makes the method especially useful for mapping the arrangement of subsurface layers and estimating how deep bedrock or other key interfaces are. The other options don’t fit because rock color and texture aren’t determined from refraction travel times, magnetic anomalies require a magnetic survey, and porosity from waveform amplitude involves different seismic attributes beyond simple refraction time analysis.