Figure 3. Schematic seismic survey profiles and time-distance curves. A. Predicted time-distance data for bedrock with uniform velocity. Lower box represents a vertical shallow subsurface section, where the thin black curved lines show seismic wave propagation. Black arrows denote the fastest path between the seismic source and each geophone. Upper plot shows the linear time-distance profile due to uniform seismic velocity. Vp: p-wave velocity. B. Schematic seismic survey over bedrock with a velocity gradient (i.e. seismically faster rock with depth). The fastest path from the source to each geophone is curved (refracted) as it exploits faster velocities at greater depths (curved lines with arrows), resulting in a curved time-distance profile. C. Seismic velocity model comprising an upper layer with a linear velocity gradient versus depth and a lower layer with a uniform velocity. The velocity gradient in the upper layer produces the initial curve in the time-distance profile, whereas the uniform lower layer produces a linear time-distance trend in the later part of the profile. A jump in velocity can occur where these two lines meet.
Image 17201 is a 1211 by 785 pixel WebP
Uploaded:
Oct9 09
