Traveltime curves for various events
Draw arrival-time curves for the five events in Figure 6.14a.
We have for the depth to the mesa, 1900 m; height of mesa, 900 m. The traveltime curves were obtained graphically. We let stand for receiver locations.
For the reflected diffraction from (diffracted at A), the virtual source (see problem 4.1) for the event is in Figure 6.14b(i) (note that traveltime increases upward), so that
For the reflection from , we use the virtual source . We will also have a diffraction from the source (paths not shown).
For the reflected refraction from (reflected at C), we find two traveltimes and then draw a straight line through them.
For the diffraction at from ,
For the diffracted reflection from (diffracted at C), we use the image point of (not shown) so that
which gives the same curve as for the diffraction from except that it is displaced towards increased time by the difference in traveltimes for and .
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Also in this chapter
- Characteristics of different types of events and noise
- Horizontal resolution
- Reflection and refraction laws and Fermat’s principle
- Effect of reflector curvature on a plane wave
- Diffraction traveltime curves
- Amplitude variation with offset for seafloor multiples
- Ghost amplitude and energy
- Directivity of a source plus its ghost
- Directivity of a harmonic source plus ghost
- Differential moveout between primary and multiple
- Suppressing multiples by NMO differences
- Distinguishing horizontal/vertical discontinuities
- Identification of events
- Traveltime curves for various events
- Reflections/diffractions from refractor terminations
- Refractions and refraction multiples
- Destructive and constructive interference for a wedge
- Dependence of resolvable limit on frequency
- Vertical resolution
- Causes of high-frequency losses
- Ricker wavelet relations
- Improvement of signal/noise ratio by stacking