Seismic stratigraphy uses wave reflections and refractions to resolve surfaces between rock types.

Seismic stratigraphy uses wave reflections and refractions to resolve surfaces between rock types.

• A. Seismic refraction
• B. Seismic stratigraphy
• C. Magnetotellurics
• D. Electrical resistivity

Answer: (B)

Seismic stratigraphy is all about using how seismic waves behave at boundaries between different rocks to map stratigraphic surfaces. When seismic energy hits an interface where acoustic impedance changes, part of the energy reflects back to the surface and carries information about that boundary, including depth and the nature of the boundary. Refractions, which occur when waves bend as they travel along or just below a boundary with different velocities, help constrain the layer velocities and thicknesses. By interpreting both the reflected signals and any refracted arrivals, we can delineate surfaces that separate different rock types or lithologies, such as changes in lithology or unconformities. The other methods don’t focus on mapping lithologic boundaries in this way. Seismic refraction uses mainly first-arrival energy to determine velocities and depths in simple layered settings, which is less about imaging detailed stratigraphic surfaces. Magnetotellurics and electrical resistivity probe electrical properties of the subsurface rather than seismic impedance contrasts, so they don’t resolve rock-type boundaries from seismic wave behavior.

Seismic stratigraphy is all about using how seismic waves behave at boundaries between different rocks to map stratigraphic surfaces. When seismic energy hits an interface where acoustic impedance changes, part of the energy reflects back to the surface and carries information about that boundary, including depth and the nature of the boundary. Refractions, which occur when waves bend as they travel along or just below a boundary with different velocities, help constrain the layer velocities and thicknesses. By interpreting both the reflected signals and any refracted arrivals, we can delineate surfaces that separate different rock types or lithologies, such as changes in lithology or unconformities.

The other methods don’t focus on mapping lithologic boundaries in this way. Seismic refraction uses mainly first-arrival energy to determine velocities and depths in simple layered settings, which is less about imaging detailed stratigraphic surfaces. Magnetotellurics and electrical resistivity probe electrical properties of the subsurface rather than seismic impedance contrasts, so they don’t resolve rock-type boundaries from seismic wave behavior.