# Resolution of cross-dip

Series | Geophysical References Series |
---|---|

Title | Problems in Exploration Seismology and their Solutions |

Author | Lloyd P. Geldart and Robert E. Sheriff |

Chapter | 4 |

Pages | 79 - 140 |

DOI | http://dx.doi.org/10.1190/1.9781560801733 |

ISBN | ISBN 9781560801153 |

Store | SEG Online Store |

## Contents

## Problem 4.9a

Sources and are, respectively, 600 m north and 500 m east of source . Traveltimes to zero-offset geophones at , , and for a certain reflection are 1.750, 1.825, and 1.796 s. What are the dip and strike of the horizon, the average velocity being 3.25 km/s?

### Solution

The dip moveouts are s/km to the north and s/km to the east. We take the -axis east-west (see Figure 4.9a). If we apply equation (4.2b) as in problem 4.2c, we get

Using equations (4.2g,h), we find that

## Problem 4.9b

What are the changes in dip and strike if line AC has the bearing N80E?

### Solution

We use equation (4.2j) and Figure 4.2e to obtain the dip moveout along the east-west -axis when the measured moveout along the -axis with bearing N80E is 0.092 s/km. Equation (4.2j) gives

thus,

and the strike angle , that is, N60.0W. Thus, the change in line direction changes the dip about and the strike about .

## Problem 4.9c

Solve part (b) graphically.

### Solution

The graphical construction, shown reduced in Figure 4.9c, yields dip moveout of 0.145 s/km and strike of N61W.

The dip moveout 0.145 gives a dip 13.6. Thus the graphical solution gives almost exactly the same values as in part (b).

## Continue reading

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Effect of migration on plotted reflector locations | Cross-dip |

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Partitioning at an interface | Seismic velocity |

## Also in this chapter

- Accuracy of normal-moveout calculations
- Dip, cross-dip, and angle of approach
- Relationship for a dipping bed
- Reflector dip in terms of traveltimes squared
- Second approximation for dip moveout
- Calculation of reflector depths and dips
- Plotting raypaths for primary and multiple reflections
- Effect of migration on plotted reflector locations
- Resolution of cross-dip
- Cross-dip
- Variation of reflection point with offset
- Functional fits for velocity-depth data
- Relation between average and rms velocities
- Vertical depth calculations using velocity functions
- Depth and dip calculations using velocity functions
- Weathering corrections and dip/depth calculations
- Using a velocity function linear with depth
- Head waves (refractions) and effect of hidden layer
- Interpretation of sonobuoy data
- Diving waves
- Linear increase in velocity above a refractor
- Time-distance curves for various situations
- Locating the bottom of a borehole
- Two-layer refraction problem